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The basic structure of a nucleotide includes the following components:
A. amino acids.
B. tryptophan and leucine.
C. base, sugar, and phosphate.
D. mRNA, rRNA, and tRNA.
E. phosphorus and sulfur.
The classic Hershey and Chase (1952) experiment that offered evidence in support of DNA being the genetic material in bacteriophages made use of the following labeled components:
A. phosphorus and sulfur.
B. nitrogen and oxygen.
E. none of the above
Reverse transcriptase is an enzyme found in association with retroviral activity. It has the property of
A. synthesis of DNA from an RNA template.
B. synthesis of RNA from a DNA template.
C. requiring no template.
E. most lysozymes.
What are the two major components of the Tobacco Mosaic Virus?
A. RNA and DNA
B. DNA and protein
C. RNA and protein
D. lipids and nucleic acids
E. carbohydrates and nucleic acids
In the classic experiment conducted by Hershey and Chase, why was the pellet radioactive in the centrifuge tube that contained bacteria with viruses, which had been grown on medium containing 32P?
A. The bacteria were in the pellet, and they had incorporated radioactive proteins into their
B. The radioactive viruses (coats plus DNA) were in the pellet.
C. The bacteria were in the pellet, and many contained the radioactive viral DNA.
D. The radioactive protein coats of the viruses were in the pellet.
E. The radioactive viruses were in the pellet, and the bacteria were in the supernatant.
If 15 percent of the nitrogenous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine?
A. 15 percent B. 30 percent C. 70 percent D. 35 percent E. 40 percent
In an analysis of the nucleotide composition of double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true?
A. A = C
B. A = G and C = T
C. A + C = G + T
D. A + T = G + C
E. Both B and C are true.
If the GC content of a DNA molecule is 60 percent, what are the molar percentages of the four bases (G, C, T, A)?
Answer: G = 30 percent, C = 30 percent, A = 20 percent, T = 20 percent
(a) Assume that A + T/G + C equals 0.5 in one strand of DNA. What is the ratio of these bases in the complementary strand? (b) If A + G/T + C equals 0.5 in one strand, what is the ratio of these bases in the complementary strand?
At what approximate wavelengths do DNA, RNA, and proteins maximally absorb light?
Answer: 260 nm, 260 nm, and 280 nm, respectively
List two major differences between RNA and DNA at the level of the nucleotide.
Answer: ribose in RNA, deoxyribose in DNA; uracil in RNA replaces thymine in DNA
Provide an overview of the structure of Z-DNA.
Answer: left-handed helix with two antiparallel complementary strands, 1.8 nm in diameter, 12 bases per turn, zigzag configuration, and shallow major groove
Name the pyrimidines and the purines in DNA.
Answer: pyrimidines: cytosine and thymine; purines: adenine and guanine
What is the name of the precursor molecule used in nucleic acid synthesis?
During the polymerization of nucleic acids, covalent bonds are formed between neighboring nucleotides. Which carbons are involved in such bonds?
The transforming principle discovered by Griffith is RNA.
G and C are present in both DNA and RNA.
Hershey and Chase used labeled DNA and protein to determine that DNA is the genetic material in bacteria.
Avery et al. (1944) determined that DNA is the genetic material in bacteriophage.
In 1953, Watson and Crick published a paper that described the structure of DNA.
In E. coli, which terms accurately reflect the nature of replication of the chromosome?
A. bidirectional and fixed point of initiation
B. unidirectional and reciprocal
C. unidirectional and fixed point of initiation
E. bidirectional and multirepliconic
DNA polymerase III adds nucleotides
A. to the 3' end of the RNA primer.
B. to the 5' end of the RNA primer.
C. in the place of the primer RNA after it is removed.
D. to both ends of the RNA primer.
E. to internal sites in the DNA template.
Structures located at the ends of eukaryotic chromosomes are called
C. recessive mutations.
E. permissive mutations.
The discontinuous aspect of replication of DNA in vivo is caused by
A. polymerase slippage.
B. trinucleotide repeats.
C. the 5' to 3' polarity restriction.
D. topoisomerases cutting the DNA in a random fashion.
E. sister-chromatid exchanges.
List at least four enzymes known to be involved in the replication of DNA in bacteria.
DNA polymerase I, III, ligase, RNA primase, helicase, gyrase
What structural circumstance in DNA sets up the requirement for its semidiscontinuous nature of replication?
What protein is responsible for the initial step in unwinding the DNA helix during replication of the bacterial chromosome?
During DNA replication, what is the function of RNA primase?
What primary ingredients, coupled with DNA polymerase I, are needed for the in vitro synthesis of DNA?
DNA replication in vivo requires a primer with a free 3' end. What molecular species provides this 3' end, and how is it provided?
The free 3' end is provided by an RNA primer, which is provided by the enzymatic activity of RNA primase.
DNA replicates conservatively, which means that one of the two daughter double helices is “old” and the other is “new.”
DNA strand replication begins with an RNA primer.
In the Meselson and Stahl (1958) experiment, bean plants (Vicia faba) were radioactively labeled so that autoradiographs could be made of chromosomes.
A nucleosome is a structure associated with the nuclear membrane. It helps maintain a stable relationship between the extracellular matrix and the membrane itself.
A characteristic of aging cells is that their telomeres become shorter.
Telomerase is an RNA-containing enzyme that adds telomeric DNA sequences onto the ends of linear chromosomes.
Viral chromosomes exist in a variety of structures and can be made up of the following:
A. protein or lipid coding sequences.
B. DNA only.
C. DNA or RNA.
D. RNA only.
E. DNA, RNA, or protein.
In E. coli, the genetic material is composed of
A. circular, double-stranded DNA.
B. linear, double-stranded DNA.
C. RNA and protein.
D. circular, double-stranded RNA.
E. polypeptide chains.
In human chromosomes, there are satellite DNA sequences of about 170 base pairs in length that are present in tandem arrays of up to 1 million base pairs. Found mainly in centromere regions, they are called
C. alphoid families.
D. euchromatic regions.
E. telomere-associated sequences.
In addition to highly repetitive and unique DNA sequences, a third category of DNA sequences exists. What is it called and what types of elements are involved?
A. composite DNA; telomeres and heterochromatin
B. dominant DNA; euchromatin and heterochromatin
C. multiple gene family DNA; hemoglobin and 5.0S RNA
D. moderately repetitive DNA; SINEs, LINEs, and VNTRs
E. permissive DNA; centromeres and heterochromatin
Chromatin of eukaryotes is organized into repeating interactions with protein octamers called nucleosomes. Nucleosomes are composed of which class of molecules?
D. H1 histones
E. nonhistone chromosomal proteins
What is unusual about the amino acid composition of histones? How is the function of histones related to the amino acid composition? Of which histones are nucleosomes composed?
: Histones contain large amounts of positively charged amino acids such as lysine and arginine. Thus, they can bind electrostatically to the negatively charged phosphate groups of nucleotides. Nucleosomes are composed of all histones except H1.
A particular variant of the lambda bacteriophage has a double-stranded DNA genome of 51,365 base pairs. How long, in units of length measurement, would this DNA be?
List the components of a nucleosome.
Histones H2A, H2B, H3, and H4 exist as two types of tetramers: (H2A)2 + (H2B)2 and (H3)2 + (H4)2. Together, these form an octamer. Histone H1 lies outside the octamer.
What is an intron and what is the relationship between an intron and heterogeneous nuclear
What are minisatellites and microsatellites?
Describe the chromosomal conformations of fX174 and polyoma viruses.
Answer: single-stranded DNA, circular and double-stranded DNA, circular, respectively
Discuss the possible origin of mitochondria and chloroplasts.
Describe the method of replication of mtDNA.
The circular, double-stranded duplex is replicated semiconservatively.
List nuclear-encoded gene products that are essential to the biological activity of mitochondria.
DNA and RNA polymerases, initiation and elongation factors required for translation, ribosomal proteins, aminoacyl tRNA synthetases, and some RNAs
The size of chloroplast DNA is much greater than mitochondrial DNA. What accounts for the difference in size?
In contrast with euchromatin, heterochromatin contains more genes and is earlier replicating.
The E. coli chromosome is circular, double-stranded DNA.
Each human contains an identical set of VNTRs.
Mutations that arise in nature, from no particular external agent, are called
A. natural mutations.
B. induced mutations.
C. spontaneous mutations.
D. chromosomal aberrations.
E. cosmic mutations.
Nutritional mutations can be defined as
A. those mutations that do not allow an organism to grow on minimal medium, but do
allow the organism to grow on complete medium.
B. those mutations that change the composition of the medium.
C. those belonging to the group called prototrophs.
D. those mutations caused by site-specific mutagenesis.
E. all strains that are not auxotrophic.
wo formal terms used to describe categories of mutational nucleotide substitutions in DNA are
A. base analogues and frameshift.
B. error prone and spontaneous.
C. transversions and transitions.
D. euchromatic and heterochromatic.
E. sense and antisense.
Name two mutagens that are classified as base analogues.
A. acridine orange and proflavin
B. ethylmethane sulfonate and ethylmethylketone peroxide
C. ultraviolet light and cosmic radiation
D. 5-bromouracil and 2-aminopurine
E. hydroxyurea and peroxidase
A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be the following:
A. base analogue.
Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at “normal” rates. Such individuals are likely to suffer from
A. xeroderma pigmentosum.
D. muscular dystrophy.
E. Huntington disease.
Describe the mutagenic action of any two of the following mutagens: 5-bromouracil, proflavin, ultraviolet light.
Three human disorders—fragile-X syndrome, myotonic dystrophy, and Huntington disease— are conceptually linked by a common mode of molecular upset. Describe the phenomena that link these disorders.
What is meant by the term photoreactivation repair?
Describe how acridine dyes cause frameshift mutations.
Intercalation between bases of intact DNA causes DNA polymerase to add or skip a base during replication.
Regarding the nature of the ABO blood groups, what condition leads to the O blood type?
What is the common influence of ultraviolet light on DNA?
One type of mutation involves the replacement of a purine with a purine, while another causes the replacement of a pyrimidine with a purine. What general terms are associated with these two mutational phenomena?
The shorter the wavelength of a radiation source, the greater its likelihood of causing damage.
Acridine orange is an alkylating agent.
When using the attached-X method of mutation assessment in Drosophila, sons inherit their X chromosome from their mother and their Y chromosome from their father.
A missense mutation causes premature chain (protein) termination.
Strand discrimination during the process of DNA repair is based on DNA methylation in E. coli.
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