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If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants?
Clone the plant.
Which of the following defines a genome?
the complete set of an organism's genes and other DNA sequences
Asexual reproduction occurs during _____.
Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?
Which of the following is a true statement about sexual vs. asexual reproduction?
In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.
Which of the following is true of a species that has a chromosome number of 2n = 16?
Each diploid cell has eight homologous pairs.
Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life cycles have in common?
I. Alternation of generations
II, III, and IV
In a plant's sexual life cycle _____.
gametophytes produce gametes by mitosis
Which of the following is an example of alternation of generations?
A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
A given organism has 46 chromosomes in its karyotype. Therefore, we can conclude that it must _____.
have gametes with 23 chromosomes
A triploid cell contains sets of three homologous chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following?
63 chromosomes in 21 sets of 3
Which of the following might result in a human zygote with 45 chromosomes?
an error in either egg or sperm meiotic anaphase
In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?
length, centromere position, staining pattern, and traits coded for by their genes
Which of the life cycles is typical for animals?
Which of the life cycles is typical for plants and some algae?
Which of the life cycles is typical for most fungi and some protists?
Homologous chromosomes _____.
carry information for the same traits
If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?
The human X and Y chromosomes _____.
include genes that determine an individual's sex
Which of these is a karyotype?
organized images of a cell’s chromosomes
If a cell has completed meiosis I and is just beginning meiosis II, which of the following is an appropriate description of its contents?
It has half the amount of DNA as the cell that began meiosis.
The somatic cells of a privet shrub each contain 46 chromosomes. How do privet chromosomes differ from the chromosomes of humans ,who also have 46?
Genes of privet chromosomes are significantly different than those in humans.
After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.
haploid, and the chromosomes are each composed of two chromatids
How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have _____.
half the number of chromosomes and one-fourth the amount of DNA.
Which of the following happens at the conclusion of meiosis I?
Homologous chromosomes of a pair are separated from each other.
Sister chromatids separate from each other during _____.
mitosis and meiosis II
Which of the following occurs in meiosis but not in mitosis?
synapsis of chromosomes
When we first see chiasmata under a microscope, we know that _____.
prophase I is occurring
Homologous chromosomes are aligned at the equator of the spindle.
Centromeres of sister chromatids disjoin and chromatids separate.
Which diagram represents anaphase I of meiosis?
Which diagram represents anaphase II of meiosis?
Which sample of DNA might be from a nerve cell arrested in G0 of the cell cycle?
Which sample might represent an animal cell in the G2 phase of the cell cycle?
Which sample might represent a zygote?
A certain female's number 12 chromosomes both have the blue gene and number 19 chromosomes both have the long gene. As cells in her ovaries undergo meiosis, her resulting eggs (ova) may have which of the following?
one chromosome 12 with one blue gene and one chromosome 19 with one long gene
If a female of this species has one chromosome 12 with a blue gene and another chromosome 12 with an orange gene, and has both number 19 chromosomes with short genes, she will produce which of the following egg types?
one-half blue short and one-half orange short gene eggs
A female with a paternal set of one orange and one long gene chromosome and a maternal set comprised of one blue and one short gene chromosome is expected to produce which of the following types of eggs after meiosis?
Each egg has a one-fourth chance of having either blue long, blue short, orange long, or orange short combinations.
Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?
Which of the following can occur by the process of meiosis but not mitosis?
Diploid cells form haploid cells.
In meiosis, homologous chromosomes are separated during _____.
In meiosis, homologous chromosomes are separated during _____.
What is a major difference between meiosis II and mitosis in a diploid animal?
Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells.
What is a major difference between mitosis and meiosis I in a diploid organism?
Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.
For the duration of meiosis I, each chromosome _____.
consists of two sister chromatids joined by a centromere
Homologous pairs of chromosomes align opposite of each other at the equator of a cell during _____.
Centromeres split and sister chromatids migrate to opposite poles in meiosis _____.
Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?
Independent assortment of chromosomes occurs during _____.
For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?
Independent assortment of chromosomes is a result of _____.
the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I
When homologous chromosomes cross over, what occurs?
Corresponding segments of non-sister chromatids are exchanged.
How is natural selection related to sexual reproduction as opposed to asexual reproduction?
Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction.
The diploid number of a roundworm species is 4. Assuming there is no crossover, and random segregation of homologues during meiosis, how many different possible combinations of chromosomes might there be in the offspring (not including variety generated by crossing over)?
The bulldog ant has a diploid number of two chromosomes. Therefore, following meiosis, each daughter cell will have a single chromosome. Diversity in this species may be generated by mutations and _____.
crossing over and independent assortment
The fastest way for organisms to adapt to a changing environment involves _____.
Imagine that there are twenty-five different species of protists living in a tide pool. Some of these species reproduce both sexually and asexually, and some of them can reproduce only asexually. The pool gradually becomes infested with disease-causing viruses and bacteria. Which species are more likely to thrive in the changing environment?
the sexually reproducing species
n eukaryotes, genetic information is passed to the next generation by processes that include mitosis or meiosis. Which of the explanations identifies the correct process and supports the claim that heritable information is passed from one generation to another?
In asexual reproduction, a single individual is the sole parent and passes copies of its genes to its offspring without the fusion of gametes.
Genetic variation leads to genetic diversity in populations and is the raw material for evolution. Biological systems have multiple processes, such as reproduction, that affect genetic variation. They are evolutionarily conserved and shared by various organisms.
Which statement best represents the connection between reproduction and evolution?
Sexual reproduction increases genetic variation because random mutations can be shuffled between organisms.
What do we mean when we use the terms monohybrid cross and dihybrid cross?
A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
Traits are inherited in discrete units and are not the results of "blending."
How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?
different possible assortment of chromosomes into gametes
Mendel continued some of his experiments into the F2 or F3 generation to _____.
observe whether or not a recessive trait would reappear
Which of the following statements about independent assortment and segregation is correct?
The law of independent assortment requires describing two or more genes relative to one another.
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
Mendel accounted for the observation that traits that had disappeared in the F1 generation reappeared in the F2 generation by proposing that _____.
traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1
The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
All of the genes controlling the traits behaved as if they were on different chromosomes.
Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?
anaphase I of meiosis
Mendel's second law of independent assortment has its basis in which of the following events of meiosis I?
alignment of tetrads at the equator
Which of the boxes marked 1-4 correspond to plants with dark leaves?
Which of the boxes marked 1-4 correspond to plants with a heterozygous genotype? A) 1
Which of the boxes marked 1-4 correspond to plants that will be true-breeding?
Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system?
Why did the F1 offspring of Mendel's classic pea cross always look like one of the two
Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6022 yellow and 2001
green (8023 total). The allele for green seeds has what relationship to the allele for yellow seeds?
Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first child will be an albino?
Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation and have one child out of three who is albino (without melanin pigmentation). What are the genotypes of the albino's parents?
Both parents must be heterozygous.
A black guinea pig crossed with an albino guinea pig produced twelve black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for this genetic situation?
Albino is recessive; black is dominant.
Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white.
(a) What is the most probable genotype of each parent?
(b) Based on your answer in (a) above, what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols: G = gray and g = white.)
(a) Gg × Gg; (b) genotypic = 1:2:1, phenotypic = 3:1
When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded
plants, what genotypic ratio was expected?
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?
In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
Given the parents AABBCc × AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent with genotype AABBCc?
Which of the following is the best statement of the use of the addition rule of probability?
the probability that either one of two independent events will occur
Which of the following calculations require that you utilize the addition rule?
Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both.
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. Among the F2 offspring, what is the probability of plants with white axial flowers?
A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits?
Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl?
Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring?
Suppose two AaBbCc individuals are mated. Assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the three traits?
In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?
Which of the following describes the ability of a single allele to have multiple phenotypic effects?
Which of the following is an example of polygenic inheritance?
skin pigmentation in humans
Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?
environmental factors such as soil pH
Which of the following provides an example of epistasis?
In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. If true-breeding red long radishes are crossed with true- breeding white oval radishes, the F1 will be expected to be which of the following?
purple and long
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The flower color trait in radishes is an example of which of the following?
Skin color in a certain species of fish is inherited via a single gene with four different alleles. One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4 (S2S4). If each
allele confers a unit of color darkness such that S1 has one unit, S2 has two units, and so on, then
what proportion of their offspring would be expected to have five units of color?
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. The relationship between genes S and N is an example of _____.
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce_____.
all sharp-spined progeny
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?
9 sharp-spined:3 dull-spined:4 spineless
Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white. A blue budgie is crossed with a white budgie. Which of the following results is NOT possible?
Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white. Two blue budgies were crossed. Over the years, they produced twenty-two offspring, five of which were white. What are the most likely genotypes for the two blue budgies?
yyBb and yyBb
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative. Which of the following is a possible phenotype for the father?
A gene for the MN blood group has codominant alleles M and N. If both children are of blood type M, which of the following is possible?
Each parent is either M or MN.
Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes ocular problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?
It is pleiotropic.
In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces black fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur?
In humans, ABO blood types refer to glycoproteins in the membranes of red blood cells. There are three alleles for this autosomal gene: IA, IB, and i. The IA allele codes for the A glycoprotein, The IB allele codes for the B glycoprotein, and the i allele doesn't code for any membrane glycoprotein. IA and IB are codominant, and i is recessive to both IA and IB. People with type A blood have the genotypes IAIA or IAi, people with type B blood are IBIB or IBi, people with type AB blood are IAIB, and people with type O blood are ii. If a woman with type AB blood marries a man with type O blood, which of the following blood types could their children possibly have?
An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?
amniocentesis or CVS
In some parts of Africa, the frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?
Darwin's explanation of natural selection
Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize the amino acid phenylalanine. This amino acid is not naturally produced by humans. Therefore, the most efficient and effective treatment is which of the following?
Regulate the diet of the affected persons to severely limit the uptake of the amino acid.
Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of 13 years. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption?
The disorder may be due to mutation in a single protein-coding gene.
One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. Which of the following is the best explanation for why a young, affected child is the first in her family to be diagnosed?
One of the parents has a mild expression of the gene.
What is the genotype of individual II-5?
What is the likelihood that the progeny of IV-3 and IV-4 will have the trait?
What is the probability that individual III-1 is Ww?
From this pedigree, this trait seems to be inherited _____.
as an autosomal dominant
Which of the following statements is a correct explanation for the observation that all offspring exhibit a phenotype for a particular trait that appears to be a blend of the two parental varieties?
Neither of the parental genes is dominate over the other.
When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2
generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early twentieth century?
Mendelian genes are at specific loci on the chromosome and, in turn, segregate during meiosis.
Males are more often affected by sex-linked traits than females because _____.
males are hemizygous for the X chromosome
SRY is best described as _____.
a gene region present on the Y chromosome that triggers male development
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
XNXn and XNY
Cinnabar eyes is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have
Normally, only female cats have the tortoiseshell phenotype because _____.
a male inherits only one allele of the X-linked gene controlling hair color
In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female?
Sex determination in mammals is due to the SRY gene. Which of the following could allow a person with an XX karyotype to develop a male phenotype?
translocation of SRY to a X chromosome
In humans, clear gender differentiation occurs, not at fertilization, but after the second month of gestation. What is the first event of this differentiation?
Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their twenties. How likely is it for a woman to have this condition?
One-half of the daughters of an affected father and a carrier mother could have this condition.
All female mammals have one active X chromosome per cell instead of two. What causes this?
activation of the XIST gene on the X chromosome that will become the Barr body
A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X- linked recessive. How many of their daughters might be expected to be color-blind dwarfs?
A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X- linked recessive. What proportion of their sons would be color-blind and of normal height?
Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex-linked or autosomal?
In birds, sex is determined by a ZW chromosome scheme that is much like the typical XY scheme seen in humans and many other organisms, except that the system is reversed: Males are ZZ (similar to XX in humans) and females are ZW (similar to XY in humans). A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female?
A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind marries a color-blind male. What is the probability that this couple's first son will be color blind?
A man who carries an allele of an X-linked gene will pass it on to _____.
Glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as a recessive allele of an X-linked gene in humans. A woman whose father suffered from G6PD marries a normal man. (a) What proportion of their sons is expected to be G6PD?
(b) If the husband was not normal but was G6PD deficient, would you change your answer in part (a)?
In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F1s were phenotypically wild type. However, adult flies of the F2 generation (resulting from matings of the F1s) had the characteristics shown in the figure above. Consider the following questions:
(a) Is the mutant allele for yellow body recessive or dominant? (b) Is the yellow locus autosomal (not X-linked) or X-linked?
Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways?
Which of the following statements is true of linkage?
The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
How would one explain a testcross involving F1 dihybrid flies in which more parental-type
offspring than recombinant-type offspring are produced?
What does a frequency of recombination of 50% indicate?
What is the definition of one map unit?
Recombination between linked genes comes about for what reason?
Crossovers between these genes result in chromosomal exchange.
What is an adaptive advantage of recombination between linked genes?
Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?
Between which two genes would you expect the highest frequency of recombination?
In a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in the figure above. What is the order of these genes on a chromosome map?
Which of the following are the phenotypes of the parents in this cross?
Which of the progeny phenotypes will require recombination between genes A and B?
If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?
What is the greatest benefit of having used a testcross for this experiment?
The phenotypes of the progeny reveal the allelic content of the gamete from the heterozygous parent.
The greatest distance among the three genes is between a and c. What does this mean?
Genes are in the order: a—b—c.
What is the reason that closely linked genes are typically inherited together?
A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers. The F1 all had red fruit and
yellow flowers. The F1 were testcrossed by crossing them to homozygous recessive individuals and the following offspring were obtained:
Red fruit and yellow flowers—41 Red fruit and white flowers—7 Golden fruit and yellow flowers—8 Golden fruit and white flowers—44
How many map units separate these genes?
In Drosophila melanogaster, vestigial wings are caused by a recessive allele of a gene that is linked to a gene with a recessive allele that causes black body color. Morgan crossed black- bodied, normal-winged females and gray-bodied, vestigial-winged males. The F1 were all gray
bodied, normal winged. The F1 females were crossed to homozygous recessive males to produce testcross progeny. Morgan calculated the map distance to be 17 map units. Which of the
following is correct about the testcross progeny?
gray-bodied, normal-winged flies PLUS black-bodied, vestigial-winged flies = 17% of the total
One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?
A nonreciprocal crossover causes which of the following products?
Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?
A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4 that has been exchanged with a portion of his chromosome 12. Although his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?
1/4 will carry the two normal chromosomes, 4 and 12, 1/4 will have only the two translocation chromosomes and no normal chromosomes 4 and 12, and 1/2 will have both normal and translocated chromosomes.
Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?
A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?
What is a syndrome?
a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation
Which of the following is generally true of aneuploidies in newborns?
Monosomy X is the only viable monosomy known to occur in humans.
A woman is found to have forty-seven chromosomes, including three X chromosomes. Which of the following describes her expected phenotype?
Which of the following is an example of monosomy?
Correns found that the inheritance of variegated color on the leaves of certain plants was determined only by the maternal parent. What phenomenon explains this pattern?
Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect _____.
The pedigree in the figure above shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely _____.
A certain kind of snail can have a right-handed direction of shell coiling (DD or Dd) or left- handed coiling (dd). However, if direction of coiling is due to a protein deposited by the mother in the egg cytoplasm, then a Dd egg-producing snail and a dd sperm-producing snail will have offspring of which genotype(s) and phenotype(s)?
During meiosis, a defect occurs in a cell that results in the failure of microtubules, spindle fibers, to bind at the kinetochores, a protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart. Which of the following is the most likely result of such a defect?
The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy.
Inheritance patterns cannot always be explained by Mendel’s models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice
that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?
In his transformation experiments, what did Griffith observe?
Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
How do we describe transformation in bacteria?
assimilation of external DNA into a cell
After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?
phosphorescence in descendants of the living cells
In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
DNA contains phosphorus, whereas protein does not.
Which of the following investigators was (were) responsible for the following discovery?
In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
In an analysis of the nucleotide composition of DNA, which of the following will be found?
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell
In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and _____ of the last nucleotide in the polymer.
Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many
What is meant by the description "antiparallel" regarding the strands that make up DNA?
The 5' to 3' direction of one strand runs counter to the to direction of the other strand.
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?
No replication fork will be formed.
In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the → direction?
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?
gaps left at the end of the lagging strand
How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?
It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.
The DNA of telomeres has been highly conserved throughout the evolution of eukaryotes. This most likely reflects _____.
a critical function of telomeres
At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork:
C C T AG GC T G C A AT C C
An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?
5' A C G U U A G G 3'
In E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
nuclease, DNA polymerase I, DNA ligase
In E. coli, what is the function of DNA polymerase III?
to add nucleotides to the 3' end of a growing DNA strand
The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that _____.
the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose
The leading and the lagging strands differ in that _____.
the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction
A new DNA strand elongates only in the 5' to 3' direction because _____.
DNA polymerase can add nucleotides only to the free 3' end
What is the function of topoisomerase?
relieving strain in the DNA ahead of the replication fork
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
It joins Okazaki fragments together.
Which of the following help(s) to hold the DNA strands apart while they are being replicated?
single-strand DNA binding proteins
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells cannot_____
Which of the following would you expect of a eukaryote lacking telomerase?
a reduction in chromosome length in gametes
In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure
above would be expected after one round of DNA replication in the presence of 14N?
A space probe returns with a culture of a microorganism found on a distant planet. Analysis
shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for
several generations and then transfer them to 14N medium. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?
After the first replication was observed in their experiments testing the nature of DNA replication, Meselson and Stahl could be confident of which of the following conclusions?
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent _____.
Within a double-stranded DNA molecule, adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine. This arrangement _____.
Semiconservative replication involves a template. What is the template?
DNA is synthesized through a process known as _____.
Who performed classic experiments that supported the semiconservative model of DNA replication?
DNA contains the template needed to copy itself, but it has no catalytic activity in cells. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?
What provides the energy for the polymerization reactions in DNA synthesis?
the deoxyribonucleotide triphosphate substrates
Refer to the figure above. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the new strand in the order that they will be added starting at the 3' end of the primer.
A, G, A, C, G, A, C
What is the difference between the leading strand and the lagging strand in DNA replication?
The leading strand is synthesized continuously in the 5'→3' direction, while the lagging strand is synthesized discontinuously in the 5'→3'direction.
What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?
Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.
What is a telomere?
the ends of linear chromosomes
Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. How might adding telomerase affect cellular aging?
Telomerase eliminates telomere shortening and retards aging.
Telomere shortening is a problem in which types of cells?
Which of the following cells have reduced or very little active telomerase activity?
Researchers found E. coli that had mutation rates one hundred times higher than normal. Which of the following is the most likely cause of these results?
The proofreading mechanism of DNA polymerase was not working properly.
In a healthy cell, the rate of DNA repair is equal to the rate of DNA mutation. When the rate of repair lags behind the rate of mutation, what is a possible fate of the cell?
The cell can be transformed to a cancerous cell.
Which of the following statements describes a eukaryotic chromosome?
a single linear molecule of double-stranded DNA plus proteins
If a cell were unable to produce histone proteins, which of the following would be a likely effect?
The cell's DNA couldn't be packed into its nucleus.
Which of the following statements is true of histones?
Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
Why do histones bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged.
Which of the following represents the order of increasingly higher levels of organization of chromatin?
nucleosome, 30-nm chromatin fiber, looped domain
Which of the following statements describes chromatin?
Heterochromatin is highly condensed, whereas euchromatin is less compact.
Which of the following is most critical for the association between histones and DNA?
Histones are positively charged.
In E. coli replication the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA
polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following would you expect?
Replication would not occur on either the leading or lagging strand.
Hershey and Chase used a DNA-based virus for their work. What would the results have been if they had used an RNA virus?
With an RNA virus radioactive RNA would have been in the final pellet.
The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki
fragments gave evidence for which of the following ideas?
DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because _____.
genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is _____.
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A gene from an organism can theoretically be expressed by any other organism.
The figure above shows a simple metabolic pathway. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
Refer to the metabolic pathway illustrated above. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on medium supplemented with _____.
Refer to the metabolic pathway illustrated above. If A, B, and C are all required for growth, a strain mutant for the gene-encoding enzyme B would be able to grow on medium supplemented with _____.
A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be _____.
What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3'
Refer to the figure above. What would the anticodon be for a tRNA that transports phenylalanine to a ribosome?
Which of the following contradicts the one-gene, one-enzyme hypothesis?
A single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally.
Which of the following is directly related to a single amino acid?
the three-base sequence of mRNA
In the process of transcription, _____.
Codons are part of the molecular structure of _____.
What does it mean when we say the genetic code is redundant?
More than one codon can specify the addition of the same amino acid.
Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukarotes?
Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.
According to the central dogma, what molecule should go in the blank? DNA → _____ → Proteins
Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?
Codons are a nearly universal language among all organisms.
Which of the following occurs in prokaryotes but not in eukaryotes?
concurrent transcription and translation
Which of the following statements best describes the termination of transcription in prokaryotes?
RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?
RNA polymerase II
Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
several transcription factors
Which of the following best describes the significance of the TATA box in eukaryotic promoters?
It is the recognition site for a specific transcription factor.
Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?
A cap is added to the 5'end of the mRNA.
A ribozyme is _____.
an RNA with catalytic activity
Alternative RNA splicing _____.
can allow the production of proteins of different sizes and functions from a single mRNA
In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
the various domains of the polypeptide product
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its cap and poly-A tail. Which of the following would you expect her to find?
The molecule is digested by enzymes because it is not protected at the 5' end.
Which components of the previous molecule will also be found in mRNA in the cytosol?
Which one of the following statements about RNA processing is true?
Ribozymes may function in RNA splicing.
A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA.
larger than; the same size as
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is _____.
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____.
binding of the anticodon to the codon and the attachment of amino acids to tRNAs
A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that _____.
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU
There are sixty-one mRNA codons that specify an amino acid, but only forty-five tRNAs. This is best explained by the fact that _____.
the rules for base pairing between the third base of a codon and tRNA are flexible
Which of the following is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
A signal peptide _____.
helps target a protein to the ER
The release factor (RF) _____.
binds to the stop codon in the A site in place of a tRNA
The dipeptide that will form will be _____.
The anticodon loop of the first tRNA that will complement this mRNA is
What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure above?
The figure above represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?
The tRNA shown in the figure above has its 3' end projecting beyond its occur at this 5' end?
The amino acid binds covalently.
What must occur before a newly made polypeptide is secreted from a cell?
Its signal sequence must target it to the ER, after which it goes to the Golgi.
Translation requires _____.
mRNA, tRNA, and rRNA
During elongation, which site in the ribosome represents the location where a codon is being read?
Once a peptide has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?
Which one of the following, if missing, would usually prevent translation from starting?
Put the following events of elongation in prokaryotic translation in chronological order. 1. Binding of mRNA with small ribosomal subunit
2. Recognition of initiation codon
3. Complementary base pairing between initiator codon and anticodon of initiator tRNA
4. Base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5. Attachment of the large subunit
How does termination of translation take place?
A stop codon is reached.
Post-translational modifications of proteins may include the _____.
addition of carbohydrates to form a glycoprotein
Which of the following statements is true about protein synthesis in prokaryotes?
Translation can begin while transcription is still in progress.
Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
A nonsense mutation in a gene _____.
introduces a premature stop codon into the mRNA
Which of the following DNA mutations is most likely to damage the protein it specifies?
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in _____
a polypeptide missing an amino acid
Of the following, which is the most current description of a gene?
a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?
Only a single amino acid could change, because the reading frame is unaffected.
An original section of DNA has the base sequence AGCGTTACCGT. A mutation in this DNA strand results in the base sequence AGGCGTTACCGT. This change represents _____.
A single base substitution mutation is least likely to be deleterious when the base change results in _____.
a codon that specifies the same amino acid as the original codon
Rank the following one-base point mutations (from most likely to least likely) with respect to their likelihood of affecting the structure of the corresponding polypeptide.
1. insertion mutation deep within an intron
2. substitution mutation at the third position of an exonic codon
3. substitution mutation at the second position of an exonic codon 4. deletion mutation within the first exon of the gene
Which of the following is a protein produced by a regulatory gene?
A lack of which molecule would result in a cell's inability to "turn off" genes?
Which of the following, when taken up by a cell, binds to a repressor so that the repressor no longer binds to the operator?
Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?
A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result in _____.
continuous transcription of the structural gene controlled by that regulator
The lactose operon is likely to be transcribed when _____.
the cyclic AMP and lactose levels are both high within the cell
Transcription of structural genes in an inducible operon _____.
starts when the pathway's substrate is present
For a repressible operon to be transcribed, which of the following must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____.
allowing an organism to adjust to changes in environmental conditions
In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP activity in stimulating transcription?
a decrease in glucose and an increase in cAMP
There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?
If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely?
Beta galactosidase will not be produced.
If she moves the operator to the far end of the operon, past the transacetylase (lacA) gene, which of the following would likely occur when the cell is exposed to lactose?
The structural genes will be transcribed continuously.
If she moves the repressor gene (lacI), along with its promoter, to a position at some several thousand base pairs away from its normal position, we would expect the _____.
lac operon will function normally
What would occur if the repressor of an inducible operon were mutated so that it could not bind the operator?
According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?
The lac operon would be transcribed continuously.
The trp repressor blocks transcription of the trp operon when the repressor _____.
binds to tryptophan
Extracellular glucose inhibits transcription of the lac operon by _____.
reducing the levels of intracellular cAMP
CAP is said to be responsible for positive regulation of the lac operon because _____.
CAP bound to the CAP-binding site increases the frequency of transcription initiation
Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?
The mutant will show low levels of gene expression.
The primary difference between enhancers and promoter-proximal elements is that enhancers _____.
are at considerable distances from the promoter; promoter-proximal elements are close to the promoter
The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.
Gene expression is often assayed by measuring the level of mRNA produced from a gene. If one is interested in knowing the amount of a final active gene product, a potential problem of this method is that it ignores the possibility of _____.
Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread _____.
One way to detect alternative splicing of transcripts from a given gene is to _____.
compare the sequences of different mRNAs made from the given gene
Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?
The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time.
DNA methylation and histone acetylation are examples of _____.
In eukaryotes, general transcription factors _____
bind to other proteins or to the TATA box
Steroid hormones produce their effects in cells by _____.
binding to intracellular receptors and promoting transcription of specific genes
Which of the following is most likely to have a small protein called ubiquitin attached to it?
a cyclin protein, that usually acts in G1, in a cell that is in G2
In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?
decreased chromatin condensation
One of her colleagues suggested she try increased methylation of C nucleotides in the DNA of promoters of a mammalian system. Which of the following results would she most likely see?
inactivation of the selected genes
Which method is utilized by eukaryotes to control their gene expression that is NOT used in bacteria?
control of both RNA splicing and chromatin remodeling
The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called _____.
At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. Many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is not coding for proteins?
non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons. These are known as _____.
Which of the following best describes siRNA?
a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
Some time later, she finds that the introduced strand separates into single-stranded RNAs, one of which is degraded. What does this enable the remaining strand to do?
bind to complementary regions of target mRNAs
When she finds that the introduced strand separates into single-stranded RNAs, what other evidence of this single-stranded RNA piece's activity can she find?
The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
The fact that plants can be cloned from somatic cells demonstrates that _____.
differentiated cells retain all the genes of the zygote
Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?
The product of the bicoid gene in Drosophila provides essential information about _____.
If a Drosophila female has a homozygous mutation for a maternal effect gene, _____.
all of her offspring will show the mutant phenotype, regardless of their genotype
Mutations in which of the following genes lead to transformations in the identity of entire body parts?
Which of the following are maternal effect genes that control the orientation of the egg and thus the Drosophila embryo?
The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?
Anterior structures would form in both ends of the embryo.
In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?
genes involved in control of the cell cycle
A cell is considered to be differentiated when it _____.
produces proteins specific to a particular cell type
When the Bicoid protein is expressed in Drosophila, the embryo is still syncytial (divisions between cells are not yet fully developed). This information helps to explain which observation by Nüsslein-Volhard and Wieschaus?
Bicoid protein diffuses throughout the embryo in a concentration gradient.
The protein of the bicoid gene in Drosophila determines the _____ of the embryo.
Which of the following types of mutation would convert a proto-oncogene into an oncogene?
a mutation that greatly increases the amount of the proto-oncogene protein
stimulate normal cell growth and division
The product of the p53 gene _____.
inhibits the cell cycle
Tumor-suppressor genes _____.
encode proteins that help prevent uncontrolled cell growth
BRCA1 and BRCA2 are considered to be tumor-suppressor genes because _____.
their normal products participate in repair of DNA damage
Forms of the Ras protein found in tumors usually cause which of the following?
excessive cell division
A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer?
In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?
genes involved in control of the cell cycle
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