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In the ABO blood-type phenotype, which gene is the most epistatic?
Sex-influenced traits are encoded by ________ genes and sex-linked traits are encoded by _______ genes.
Yeast mitochondria have a tubular morphology. In a mutagenic screen, two mutants are isolated that have fragmented mitochondria instead of tubular mitochondria. To determine if these two mutations are at the same or different loci, the two mutants are crossed. The progeny all have tubular mitochondria. What do you conclude?
The mutations are at different loci.
What DNA modification is important to understand Prader–Willi syndrome?
While studying a new human disease you discover that the disease is linked to a mitochondrial gene. You can be reasonably sure that the disease is inherited _____________________.
When studying Arabidopsis a researcher isolates a gene mutation that produces a shorter stem-height phenotype. Interestingly, when this gene is present (wild-type plant) and the seedling is germinated at the lower temperature of 12°C, the same short-stem phenotype is replicated. This phenomenon is known as
In analyzing continuous characteristics, one cannot observe Mendelian ratios. The reason for this is that continuous characteristics ___________.
the percentage of individuals with a particular genotype that express the expected phenotype
a trait determined by an autosomal gene that is expressed in only one sex
the genotype of the maternal parent influences the phenotype of the offspring
the expression of a trait is affected by the sex of the parent that transmits the gene to the offspring
a trait determined by an autosomal gene that is more easily expressed in one sex
Embryonic lethal alleles cannot be dominant. T or F
. At a single genetic locus, a diploid individual may have more than two different alleles. True or False
For a given species, sex-influenced traits are expressed in only one sex and have zero penetrance in the other sex. T or F.
1. Which is NOT one of the reasons that adoption studies are useful in determining the importance of the environment on a particular trait?
Adoption agencies typically try to find adoptive parents that are genetically similar to the biological parents.
What three factors complicate the task of studying the inheritance of human characteristics?
(1) Mating cannot be controlled. It is not ethical or feasible to set up controlled mating experiments.
(2) Humans have a long generation time, so it takes a long time to track inheritance of traits over more than one generation.(3) The number of progeny per mating is limited, so phenotypic ratios are uncertain
1. Who is the proband in a pedigree? Is the proband always found in the last generation of the pedigree? Why or why not?
The proband is the person of interest for whom the pedigree chart has been drawn.
The proband is not necessarily found in the last generation because the proband’s
children, or the children of the proband’s siblings, often provide information about
the genotype of the proband.
For each of the following modes of inheritance, describe the features that will be
exhibited in a pedigree in which the trait is present: autosomal recessive, autosomal
dominant, X-linked recessive, X-linked dominant, and Y-linked inheritance.
Pedigrees with autosomal recessive traits will show affected males and females
arising with equal frequency from unaffected parents. Unaffected people with an affected parent will be carriers.
Pedigrees with autosomal dominant traits will show affected males and females
arising with equal frequency from a single affected parent.
X-linked recessive traits will affect males predominantly and will be passed from an
affected male through his unaffected daughter to his grandson.
X-linked dominant traits will affect males and females and will be passed from an
affected male to all his daughters,An affected woman will pass on the trait equally to half her
daughters and half her sons.
Y-linked traits will show up exclusively in males, passed from father to son.
The two types of twins are monozygotic and dizygotic. Monozygotic twins arise
when a single fertilized egg splits into two embryos in early embryonic cleavage
divisions. They are genetically identical. Dizygotic twins arise from two different
How are adoption studies used to separate the effects of genes and environment in the study of human characteristics?
Studies of adoptees, their biological parents, and their adoptive parents separate environmental and genetic influences on traits. Adoptees share similar environments with their adoptive parents (because they live in the same house and eat similar foods), but they share 50% of their genes with each of their biological parents. If adoptees have greater similarity for a trait with their adoptive parents, then the trait is environmentally influenced. If the adoptees have greater similarity for the trait with their biological parents, then the trait is genetically influenced.
Genetic counseling provides assistance to clients by interpreting results of genetic testing and diagnosis; providing information about relevant disease symptoms, treatment, and progression; assessing and calculating the various genetic risks that the person or couple faces; and helping clients and family members cope with the stress of decision-making and facing up to the drastic changes in their lives that may be precipitated by a genetic condition.
Compare the advantages and disadvantages of amniocentesis versus chorionic villus sampling for prenatal diagnosis.
Amniocentesis samples the amniotic fluid by inserting a needle into the amniotic sac, usually performed at about 16 weeks of pregnancy, and requires culturing the fetal cells. Chorionic villus sampling can be performed several weeks earlier (10th or 11th week of pregnancy) and samples a small piece of the chorion by inserting a catheter through the vagina. Amniocentesis is relatively safe, but results are not available until week 17 or 18 of pregnancy. Chorionic villus sampling has a slightly higher risk of complication, including fetal injury, but results are available several weeks earlier.
. Many studies have suggested a strong genetic predisposition to migraine headaches, but the mode of inheritance is not clear. L. Russo and colleagues examined migraine headaches in several families, two of which are shown below (L. Russo et al. 2005. American Journal of Human Genetics 76:327–333). What is the most likely mode of inheritance for migraine headaches in these families? Explain your reasoning.
In both families, the trait is most likely dominant because it does not skip generations, and affected individuals have one affected parent. In family 2, it is not X-linked because the affected male II-8 has an unaffected daughter. For X-linked loci, an affected male would transmit the trait to all his daughters. It could be either X-linked or autosomal in family 1.
An X-linked recessive trait is never seen in females and affects ¼ of all the sons of a female carrier. T or F.
b. genetic material must be composed of many different units to account for the variability seen in nature.
that RNA was the genetic material
that protein was the genetic material in phage
new and revolutionary experimental data that they collected themselves
a ribose sugar
Bases on complementary strands are held together by hydrogen bonds.
1) The genetic material must contain complex information that encodes the phenotype.
(2) The genetic material must replicate or be replicated faithfully.
(3) The genetic material must be able to mutate to generate diversity.
What experiments demonstrated that DNA is the genetic material?
Experiments by Hershey and Chase in the 1950s using the bacteriophage T2 and E. coli cells demonstrated that DNA is the genetic material of the bacteriophage. Also, the experiments by Avery, Macleod, and McCarty demonstrated that the transforming material initially identified by Griffith was DNA.
How does an RNA nucleotide differ from a DNA nucleotide?
DNA nucleotides, or deoxyribonucleotides, have a deoxyribose sugar that lacks an oxygen molecule at the 2' - carbon of the sugar molecule. Ribonucleotides, or RNA nucleotides, have a ribose sugar with an oxygen linked to the 2'- carbon of the sugar molecule. Ribonucleotides may contain the nitrogenous base uracil, but not thymine.
DNA nucleotides contain thymine, but not uracil.
What are hairpins and how do they form?
Hairpins are a type of secondary structure found in single strands of nucleotides. The formation of hairpins occurs when sequences of nucleotides on the single strand are inverted complementary repeats of one another.
Ribose sugars have a hydroxyl on the 2′ carbon. True or False
When in an electrical field, DNA will travel toward the anode (positively charged electrode) because DNA is negatively charged. True or False
Covalent bonds connect nucleotides in a strand; noncovalent interactions hold strands into a double-stranded structure. True or False
There are three hydrogen bonds between AT pairs. True or False
There are three phosphates between each sugar in a molecule of DNA. True or False
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