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In his work with pneumonia-causing bacteria and mice, Griffith found that
A. the polysaccharide coat of bacteria caused pneumonia.
B. the protein coat from pathogenic cells was able to transform nonpathogenic cells.
C. heat-killed pathogenic cells caused pneumonia.
D. bacteriophages injected DNA into bacteria.
E. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

E

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
A. Helicases and single-strand binding proteins work at the 5' end.
B. Polymerase can work on only one strand at a time.
C. DNA polymerase can join new nucleotides only to the 3' end of a growing strand.
D. DNA ligase works only in the 3'→5' direction.
E. The origins of replication occur only at the 5' end.

C

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?
A. G = T
B. A = C
C. A + G = C + T
D. A = G
E. A + T = G + T

C

The elongation of the leading strand during DNA synthesis
A. does not require a template strand.
B. depends on the action of DNA polymerase.
C. produces Okazaki fragments.
D. occurs in the 3'→5' direction.
E. progresses away from the replication fork.

B

In a nucleosome, the DNA is wrapped around
A. histones.
B. a thymine dimer.
C. ribosomes.
D. polymerase molecules.
E. satellite DNA.

A

E. coli cells grown on 15N medium are transferred to 15N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
A. one low-density band
B. one intermediate-density band
C. one high-density and one low-density band
D. one high-density and one intermediate-density band
E. one low-density and one intermediate-density band

E

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
A. nucleotides
B. Okazaki fragments
C. primase
D. DNA ligase
E. DNA polymerase

D

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?
A. telomerase, primase, DNA polymerase
B. DNA ligase, replication fork proteins, adenylyl cyclase
C. nuclease, telomerase, primase
D. nuclease, DNA polymerase, DNA ligase
E. telomerase, helicase, single-strand binding protein

D

Meselson and Stahl cultured E. coli for several generations in a medium with a heavy isotope of nitrogen, 15N. They transferred the bacteria to a medium with a light isotope of nitrogen, 14 N. After two rounds of DNA replication, half the DNA molecules were light (both strands had 14N) and half were hybrids (15N-14N). What did the researchers conclude from these results?
A. The nitrogenous bases in DNA molecules incorporate both 15N and 14N.
B. DNA replication is semiconservative.
C. Opposite DNA strands are complementary to each other.

B

DNA is a self-replicating molecule. What accounts for this important property of DNA?
A.Replication is thermodynamically spontaneous and requires no enzymes.
B. The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C.
C. Its two strands are held together by easily broken covalent bonds.

B

Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?
A. Nucleoside triphosphates are more abundant in the cell than nucleotides.
B. Hydrolysis of the two phosphate groups (P-Pi) and DNA polymerization are a coupled exergonic reaction.
C. Nucleoside triphosphates are more easily transported in the cell than are nucleotides.

B

During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?
A. DNA synthesis can take place only in the 5' to 3' direction.
B. There are thousands of origins of replication on the lagging strand but only one on the leading strand.
C. DNA polymerases can bind to only one strand at a time.

A

Select the most accurate metaphor or simile for DNA replication complexes.
A. DNA and the DNA replication complexes fit together like a lock and key.
B. DNA replication complexes move along a DNA railway track.
C. DNA replication complexes are grouped into factories, which are anchored to the nuclear matrix.

C

Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?
A. Heat kills bacteria.
B. Protein could not be the genetic material.
C. DNA was the genetic material.
D. A virus made the bacteria pathogenic.
E. The transferred traits were heritable.

E

In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, what was the key finding?
A. Radioactively labeled phosphorus was found outside of the infected bacteria.
B. Radioactively labeled carbon was present inside the infected bacteria.
C. Radioactively labeled phosphorus was present inside the infected bacteria.
D. Radioactively labeled sulfur was found outside of the infected bacteria.
E. Radioactively labeled sulfur was present inside the infected bacteria.

C

Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?
A. Franklin
B. Meselson and Stahl
C. Chargaff
D. McClintock
E. Griffith

A

In his transformation experiments, what did Griffith observe?
A. Mutant mice were resistant to bacterial infections.
B. Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
C. Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.
D. Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.
E. Mice infected with a pathogenic strain of bacteria can spread the infection to other mice.

B

How do we describe transformation in bacteria?
A. the creation of a strand of RNA from a DNA molecule
B. assimilation of external DNA into a cell
C. the infection of cells by a phage DNA molecule
D. the type of semiconservative replication shown by DNA
E. the creation of a strand of DNA from an RNA molecule

B

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
A. DNA contains nitrogen, whereas protein does not.
B. RNA includes ribose, whereas DNA includes deoxyribose sugars.
C. DNA contains sulfur, whereas protein does not.
D. DNA contains phosphorus, whereas protein does not.
E. DNA contains purines, whereas protein includes pyrimidines.

D

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.
A. Alfred Hershey and Martha Chase
B. Erwin Chargaff
C. Frederick Griffith
D. Oswald Avery, Maclyn McCarty, and Colin MacLeod
E. Matthew Meselson and Franklin Stahl

B

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?
A. 16%
B. 8%
C. 42%
D. 31%
E. It cannot be determined from the information provided.

B

Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?
A. the frequency of A vs. T nucleotides
B. the bond angles of the subunits
C. the rate of replication
D. the sequence of nucleotides
E. the diameter of the helix

E

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?
A. phosphate-sugar backbones
B. different five-carbon sugars
C. complementary pairing of bases
D. sequence of bases
E. side groups of nitrogenous bases

D

In an analysis of the nucleotide composition of DNA, which of the following will be found?
A. A = C
B. A = G and C = T
C. G + C = T + A
D. A + C = G + T

D

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?
A. Avery et al. have already concluded that this experiment showed inconclusive results.
B. Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
C. Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
D. There is no radioactive isotope of nitrogen.
E. Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.

C

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?
A. The phosphorescence in the living strain is especially bright.
B. DNA passed from the heat-killed strain to the living strain.
C. Descendants of the living cells are also phosphorescent.
D. Protein passed from the heat-killed strain to the living strain.
E. Both DNA and protein passed from the heat-killed strain to the living strain.

C

DNA replication is said to be semiconservative. What does this mean?
A. Each new double helix consists of one old and one new strand.
B. One strand of the new double helix is made of DNA and the other strand is made of RNA.
C. One of the two resulting double helices is made of two old strands, and the other is made of two new strands.
D. Half of the old strand is degraded and half is used as a template for the replication of a new strand.
E. The old double helix is degraded and half of its nucleotides are used in the construction of two new double helices.

A

What is the function of helicase in DNA replication?
A. It checks for errors in the newly synthesized DNA strand.
B. It untwists the double helix and separates the two DNA strands.
C. It adds nucleotides to the new strand in the 5' to 3' direction.
D. It relieves strain from twisting of the double helix as it is unwound.
E. It joins together Okazaki fragments.

B

In nucleotide excision repair, damaged DNA is excised by what enzyme(s)?
A. restriction enzymes
B. ligase
C. endonuclease
D. primase
E. helicase

C

What process repairs damage to a preexisting double helix?
A. proofreading
B. transformation
C. operon repair
D. mismatch repair
E. nucleotide excision repair

E

What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?
A. telomeres
B. centromeres
C. sarcomeres
D. chromomeres
E. polypeptides

A

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
A. The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.
B. Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.
C. Prokaryotes have telomeres, and eukaryotes do not.
D. Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.
E. Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

E

What is meant by the description "antiparallel" regarding the strands that make up DNA?
A. One strand is positively charged and the other is negatively charged.
B. The twisting nature of DNA creates nonparallel strands.
C. One strand contains only purines and the other contains only pyrimidines.
D. Base pairings create unequal spacing between the two DNA strands.
E. The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

E

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?
A. All four bases of the DNA would be radioactive.
B. One of the daughter cells, but not the other, would have radioactive DNA.
C. Radioactive thymine would pair with nonradioactive guanine.
D. DNA in both daughter cells would be radioactive.
E. Neither of the two daughter cells would be radioactive.

D

An Okazaki fragment has which of the following arrangements?
A. primase, polymerase, ligase
B. DNA polymerase I, DNA polymerase III
C. 5' DNA to 3'
D. 3' RNA nucleotides, DNA nucleotides 5'
E. 5' RNA nucleotides, DNA nucleotides 3'

E

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?
A. Replication will require a DNA template from another source.
B. The DNA will supercoil.
C. No replication fork will be formed.
D. No proofreading will occur.
E. Replication will occur via RNA polymerase alone.

C

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
A. helicase
B. DNA polymerase III
C. primase
D. DNA ligase
E. topoisomerase

B

Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?
A. gaps left at the 5' end of the lagging strand
B. DNA polymerase that cannot replicate the leading strand template to its 5' end
C. the "no ends" of a circular chromosome
D. the evolution of telomerase enzyme
E. gaps left at the 3' end of the lagging strand because of the need for a primer

A

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?
A. that new evolution of telomeres continues
B. the low frequency of mutations occurring in this DNA
C. that the critical function of telomeres must be maintained
D. that mutations in telomeres are relatively advantageous
E. the inactivity of this DNA

C

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork:
3' C C T A G G C T G C A A T C C 5'
An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?
A.5' G C C T A G G 3'
B. 5' A C G T T A G G 3'
C. 3' G C C T A G G 5'
D. 5' G C C U A G G 3'
E. 5' A C G U U A G G 3'

E

Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?
A. replication followed by mitosis
B. special association with histone proteins
C. meiosis followed by mitosis
D. replication without separation
E. fertilization by multiple sperm

D

To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
A. endonuclease, DNA polymerase I, DNA ligase
B. DNA polymerase I, DNA polymerase III, DNA ligase
C. DNA ligase, nuclease, helicase
D. helicase, DNA polymerase I, DNA ligase
E. exonuclease, DNA polymerase III, RNA primase

A

What is the function of DNA polymerase III?
A. to rejoin the two DNA strands (one new and one old) after replication
B. to degrade damaged DNA molecules
C. to seal together the broken ends of DNA strands
D. to add nucleotides to the 3' end of a growing DNA strand
E. to unwind the DNA helix during replication

D

The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that
A. ATP contains three high-energy bonds; the nucleoside triphosphates have two.
B. triphosphate monomers are active in the nucleoside triphosphates, but not in ATP.
C. ATP is found only in human cells; the nucleoside triphosphates are found in all animal and plant cells.
D. the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.
E. the nucleoside triphosphates have two phosphate groups; ATP has three phosphate groups.

D

The leading and the lagging strands differ in that
A. the lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.
B. the leading strand is synthesized at twice the rate of the lagging strand.
C. 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.
D. the leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.

C

A new DNA strand elongates only in the 5' to 3' direction because
A. Okazaki fragments prevent elongation in the 3' to 5' direction.
B. DNA polymerase can only add nucleotides to the free 3' end.
C. replication must progress toward the replication fork.
D. DNA polymerase begins adding nucleotides at the 5' end of the template.
E. the polarity of the DNA molecule prevents addition of nucleotides at the 3' end.

B

What is the function of topoisomerase?
A. elongating new DNA at a replication fork by adding nucleotides to the existing chain
B. unwinding of the double helix
C. adding methyl groups to bases of DNA
D. stabilizing single-stranded DNA at the replication fork
E. relieving strain in the DNA ahead of the replication fork

E

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
A. It synthesizes RNA nucleotides to make a primer.
B. It unwinds the parental double helix.
C. It joins Okazaki fragments together.
D. It catalyzes the lengthening of telomeres.
E. It stabilizes the unwound parental DNA.

C

Which of the following help(s) to hold the DNA strands apart while they are being replicated?
A. exonuclease
B. primase
C. DNA polymerase
D. single-strand binding proteins
E. ligase

D

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?
A. They cannot exchange DNA with other cells.
B. They cannot replicate DNA.
C. They do not recombine homologous chromosomes during meiosis.
D. They cannot undergo mitosis.
E. They cannot repair thymine dimers.

E

Which of the following would you expect of a eukaryote lacking telomerase?
A. a high probability of somatic cells becoming cancerous
B. production of Okazaki fragments
C. high sensitivity to sunlight
D. a reduction in chromosome length in gametes
E. inability to repair thymine dimers

D

Use the following list of choices for the following question:

I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase
Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?
I
II
III
IV
V

IV

Use the following list of choices for the following question:
I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase
Which of the enzymes separates the DNA strands during replication?
I
II
III
IV
V

I

Use the following list of choices for the following question:
I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase
Which of the enzymes covalently connects segments of DNA?
I
II
III
IV
V

III

Use the following list of choices for the following question:
I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase
Which of the enzymes synthesizes short segments of RNA?
I
II
III
IV
V

V

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
B
C
D
E

D

Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?
A. Replication is not dispersive.
B. Replication is neither dispersive nor conservative.
C. Replication is not conservative.
D. Replication is semi-conservative.
E. Replication is not semi-conservative.

C

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
A. leading strands and Okazaki fragments.
B. RNA primers and mitochondrial DNA.
C. lagging strands and Okazaki fragments.
D. Okazaki fragments and RNA primers.
E. leading strands and RNA primers.

A

How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?
A. It adds a single 5' cap structure that resists degradation by nucleases.
B. It causes specific double-strand DNA breaks that result in blunt ends on both strands.
C. It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity.
D. It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication.
E. It causes linear ends of the newly replicated DNA to circularize.

D

Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?
A. topoisomerases, telomerases, polymerases
B. double-stranded DNA, four kinds of dNTPs, primers, origins of replication
C. G-C rich regions, polymerases, chromosome nicks
D. ligase, primers, nucleases
E. nucleosome loosening, four dNTPs, four rNTPs

B

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?
A
B
C
D
E

B

In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine). After several minutes, the DNA is switched to nonradioactive medium and is then viewed by electron microscopy and autoradiography. The figure above represents the results. It shows a replication bubble, and the dots represent radioactive material. Which of the following is the most likely interpretation of the results?
A. There are two replication forks going in opposite directions.
B. Thymidine is being added only where the DNA strands are farthest apart.
C. Thymidine is being added only at the very beginning of replication.
D. Replication proceeds in one direction only.

A

Given the damage caused by UV radiation, the kind of gene affected in those with XP is one whose product is involved with
A. breakage of cross-strand covalent bonds.
B. the removal of double-strand damaged areas.
C. causing affected skin cells to undergo apoptosis.
D. the ability to excise single-strand damage and replace it.
E. mending of double-strand breaks in the DNA backbone

D

What are chromosomes made of?
A. DNA and proteins
B. DNA, heterochromatin, and histone proteins
C. DNA
D. DNA and euchromatin
E. DNA, RNA, and proteins

A

Which of the following is true of DNA during interphase?
A. It exists as chromatin and is unavailable for gene expression.
B. It exists as chromatin and is less condensed than mitotic chromosomes.
C. It is in the form of highly condensed chromosomes; it is called heterochromatin.
D. It is in the form of highly condensed chromosomes and is unavailable for gene expression.
E. It exists as chromatin; it is completely uncoiled and loose.

B

Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules and 2 H2B molecules, and the other as 2 H3 and 2 H4 molecules. Which of the following is supported by this data?
A. The structure of H3 and H4 molecules is not basic like that of the other histones.
B. The two types of tetramers associate to form an octamer.
C. DNA can wind itself around either of the two kinds of tetramers.
D. DNA has to associate with individual histones before they form tetramers.
E. Only H2A can form associations with DNA molecules.

B

In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?
A. the metaphase chromosome
B. DNA with H1 only
C. the 10-nm chromatin fiber
D. the 30-nm chromatin fiber
E. DNA without attached histones

D

Which of the following statements describes the eukaryotic chromosome?
A. It is composed of DNA alone.
B. The nucleosome is its most basic functional subunit.
C. Active transcription occurs on heterochromatin but not euchromatin.
D. It consists of a single linear molecule of double-stranded DNA plus proteins.
E. The number of genes on each chromosome is different in different cell types of an organism.

D

If a cell were unable to produce histone proteins, which of the following would be a likely effect?
A. There would be an increase in the amount of "satellite" DNA produced during centrifugation.
B. The cell's DNA couldn't be packed into its nucleus.
C. Spindle fibers would not form during prophase.
D. Amplification of other genes would compensate for the lack of histones.
E. Pseudogenes would be transcribed to compensate for the decreased protein in the cell.

B

Which of the following statements is true of histones?
A. Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
B. Histones are found in mammals, but not in other animals or in plants or fungi.
C. The mass of histone in chromatin is approximately nine times the mass of DNA.
D. Each nucleosome consists of two molecules of histone H1.
E. The carboxyl end of each histone extends outward from the nucleosome and is called a "histone tail."

A

Why do histones bind tightly to DNA?
A. Histones are covalently linked to the DNA.
B. Histones are highly hydrophobic, and DNA is hydrophilic.
C. Histones are negatively charged, and DNA is positively charged.
D. Histones are positively charged, and DNA is negatively charged.
E. Both histones and DNA are strongly hydrophobic.

D

Which of the following represents the order of increasingly higher levels of organization of chromatin?
A. looped domain, 30-nm chromatin fiber, nucleosome
B. 30-nm chromatin fiber, nucleosome, looped domain
C. nucleosome, 30-nm chromatin fiber, looped domain
D. nucleosome, looped domain, 30-nm chromatin fiber
E. looped domain, nucleosome, 30-nm chromatin fiber

C

Which of the following statements describes chromatin?
A. Only euchromatin is visible under the light microscope.
B. Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA.
C. Heterochromatin is highly condensed, whereas euchromatin is less compact.
D. Euchromatin is not transcribed, whereas heterochromatin is transcribed.
E. Both heterochromatin and euchromatin are found in the cytoplasm.

C

Use the following information to answer the question.
A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already.
Where does tRNA #2 move to after this bonding of lysine to the polypeptide?
A. P site
B. A site
C. E site
D. directly to the cytosol
E. exit tunnel

C

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find?
A. The molecule is digested by restriction enzymes in the nucleus.
B. The molecule is digested by exonucleases since it is no longer protected at the 5' end.
C. The molecule attaches to a ribosome and is translated, but more slowly.
D. The cell recognizes the absence of the tail and polyadenylates the mRNA.
E. The mRNA could not exit the nucleus to be transcribed.

B

Which of the following molecules are produced by transcription?
Select all that apply.
A. Ribozymes
B. Ribosomal proteins
C. Messenger RNA

AC

Which of the following best describes the significance of the TATA box in eukaryotic promoters?
A. It is the recognition site for a specific transcription factor.
B. It prevents supercoiling of the DNA near the start site.
C. It sets the reading frame of the mRNA.
D. Its significance has not yet been determined.
E. It is the recognition site for ribosomal binding.

A

In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene?
A. eukaryotic tRNAs
B. a bacterial promoter sequence
C. the introns
D. eukaryotic ribosomal subunits
E. eukaryotic polymerases

B

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
A. the protein product of the promoter
B. several transcription factors
C. aminoacyl-tRNA synthetase
D. ribosomes and tRNA
E. start and stop codons

B

Which one of the following is true of tRNAs?
A. tRNAs are double-stranded.
B. There are four types of tRNA.
C. tRNAs carry special sequences known as codons.
D. Each tRNA binds a particular amino acid.
E. All of the above.

D

Why might a point mutation in DNA make a difference in the level of a protein's activity?
A. It might result in a chromosomal translocation.
B. It might exchange one serine codon for a different serine codon.
C. It might substitute a different amino acid in the active site.
D. It might substitute the N-terminus of the polypeptide for the C-terminus.
E. It might exchange one stop codon for another stop codon.

C

After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
A. introns ... exons
B. exons ... introns
C. operators ... promoters
D. silencers ... enhancers
E. promoters ... operators

A

RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such variability in RNA polymerase?
A. It could allow ribosomal subunits to assemble at faster rates.
B. It might allow the translation process to vary from one cell to another.
C. It might allow the polymerase to recognize different promoters under certain environmental conditions.
D. It could alter the rate of translation and of exon splicing.
E. It could allow the polymerase to react differently to each stop codon.

C

Use the following information to answer the question.The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer.
You add polynucleotide phosphorylase to a solution of ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be possible?
3
6
9
27
81

27

When the spliceosome binds to this transcript, where can it attach?
A. to the 5' UTR
B. to an adjacent intron and exon
C. at certain sites along an intron
D. to the exons
E. to the 3' UTR

C

What is a ribozyme?
A. a mutated ribosome
B. a biological catalyst consisting of DNA
C. an enzyme that holds open the DNA double helix while RNA polymerase adds nucleotides
D. a biological catalyst made of RNA
E. a DNA sequence near the promoter that assists in the binding of RNA polymerase

D

Which of the following is not true of RNA processing?
A. RNA splicing can be catalyzed by spliceosomes.
B. Nucleotides may be added at both ends of the RNA.
C. Exons are cut out before mRNA leaves the nucleus.
D. A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.
E. Ribozymes may function in RNA splicing.

C

The following information should be used for the question.
A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form.

The dipeptide that will form will be
A. proline-threonine.
B. cysteine-alanine.
C. glycine-cysteine.
D. alanine-alanine.
E. threonine-glycine.

A

The anticodon of a particular tRNA molecule is
A. the part of tRNA that bonds to a specific amino acid.
B. complementary to the corresponding triplet in rRNA.
C. catalytic, making the tRNA a ribozyme.
D. changeable, depending on the amino acid that attaches to the tRNA.
E. complementary to the corresponding mRNA codon.

e

Which of the following is true of transcription in domain Archaea?
A. It involves promoters are identical to those in domain Eukarya.
B. There is only one kind of RNA polymerase.
C. It produces RNA transcripts that are processed after they leave the nucleus.
D. It terminates in a manner similar to that in bacteria.
E. It is regulated in the same way as in domain Bacteria.

B

Which of the following statements best describes the termination of transcription in prokaryotes?
A. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase.
B. RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
C. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.
D. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome.
E. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript.

B

Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.
Select all that apply.
A. The amino acid glycine
B. RNA polymerase
C. Aminoacyl-tRNA synthetase

BC

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?
A. an assembled ribosome with a separated polypeptide
B. separated ribosomal subunits, a polypeptide, and free tRNA
C. an assembled ribosome with a polypeptide attached to the tRNA in the P site
D. a cell with fewer ribosomes
E. separated ribosomal subunits with a polypeptide attached to the tRNA

C

Which of the following is not true of a codon?
A. It consists of three nucleotides.
B. It is the basic unit of the genetic code.
C. It extends from one end of a tRNA molecule.
D. It may code for the same amino acid as another codon.
E. It never codes for more than one amino acid.

C

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?
A. RNA polymerase III
B. RNA polymerase II
C. primase
D. ligase
E. RNA polymerase I

B

What is a ribozyme?
A. an RNA with enzymatic activity
B. an enzyme that synthesizes RNA primers during DNA replication
C. an enzyme that uses RNA as a substrate
D. an enzyme that catalyzes the association between the large and small ribosomal subunits
E. an enzyme that synthesizes RNA as part of the transcription process

A

What is the effect of a nonsense mutation in a gene?
A. It introduces a premature stop codon into the mRNA.
B. It alters the reading frame of the mRNA.
C. It has no effect on the amino acid sequence of the encoded protein.
D. It prevents introns from being excised.
E. It changes an amino acid in the encoded protein.

A

Use the following information to answer the question.
A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already.
Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?
A. initiation and elongation factors
B. tRNA that no longer has attached amino acid
C. newly formed polypeptide
D. tRNA with attached lysine (#1)
E. tRNA with polypeptide (#2)

C

What is the function of GTP in translation?
A. GTP supplies phosphates and energy to make ATP from ADP.
B. GTP energizes the formation of the initiation complex, using initiation factors.
C. GTP separates the small and large subunits of the ribosome at the stop codon.
D. GTP hydrolyzes to provide phosphate groups for tRNA binding.
E. GTP hydrolyzes to provide energy for making peptide bonds.

B

An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result?
A. The aminoacylsynthetase will not be formed.
B. The anticodon will not bind with the mRNA codon.
C. The amino acid methionine will not bind.
D. tRNA will not form a cloverleaf.
E. The nearby stem end will pair improperly.

C

Which of the following is a function of a poly-A signal sequence?
A. It is a sequence that codes for the hydrolysis of the RNA polymerase.
B. It adds a 7-methylguanosine cap to the 3' end of the mRNA.
C. It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10-35 nucleotides away.
D. It allows the 3' end of the mRNA to attach to the ribosome.
E. It adds the poly-A tail to the 3' end of the mRNA.

C

A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate?
A. The sequence is transcribed at the start of every gene.
B. Any mutation in the sequence is selected against.
C. The sequence does not mutate.
D. The sequence is found in many but not all promoters.
E. The sequence evolves very rapidly.

B

The figure 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?
UGG
UUC
GUA
CAU
GUG

UUC

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that
A. many nucleotides are needed to code for each amino acid.
B. there are termination exons near the beginning of mRNA.
C. many noncoding stretches of nucleotides are present in eukaryotic DNA.
D. there is redundancy and ambiguity in the genetic code.
E. nucleotides break off and are lost during the transcription process.

C

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
A. a codon substitution
B. a codon deletion
C. a base-pair deletion
D. a substitution in the last base of a codon
E. a point mutation

C

Which component is not directly involved in translation?
A. GTP
B. ribosomes
C. tRNA
D. mRNA
E. DNA

E

What is the function of RNA polymerase?
A. It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule.
B. It unwinds the double helix and adds nucleotides to a growing strand of RNA.
C. It adds nucleotides to the 5' end of the growing mRNA molecule.
D.It relies on other enzymes to unwind the double helix.
E. All of the above.

B

Alternative RNA splicing
A. can allow the production of similar proteins from different RNAs.
B. can allow the production of proteins of different sizes and functions from a single mRNA.
C. is a mechanism for increasing the rate of transcription.
D. increases the rate of transcription.
E. is due to the presence or absence of particular snRNPs.

B

Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell?
A. methylation of C nucleotides
B. removal of one or more exons
C. methylation of histones
D. enzymatic lengthening of the poly-A tail
E. removal of the 5' cap

E

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
A. UUA.
B. AAA.
C. TTT.
D. UUU.
E either UAA or TAA, depending on first base wobble.

D

Which of the following is the first event to take place in translation in eukaryotes?
A. binding of the larger ribosomal subunit to smaller ribosomal subunits
B. base pairing of activated methionine-tRNA to AUG of the messenger RNA
C. elongation of the polypeptide
D. covalent bonding between the first two amino acids
E. the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

E

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A. The same codons in different organisms translate into the different amino acids.
B. A gene from an organism can theoretically be expressed by any other organism.
C. DNA was the first genetic material.
D. All organisms have experienced convergent evolution.
E. Different organisms have different numbers of different types of amino acids.

B

How is translation initiated?
A. The small ribosomal subunit binds to the mRNA.
B. The tRNA bearing methionine binds to the start codon.
C. The large ribosomal subunit binds to the small one.
D. The start codon signals the start of translation.
E. All of the above.

E

A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
A. four ... amino acid
B. three ... amino acid
C. three ... nucleotide
D. two ... nucleotide
E. four ... fatty acid

B

If a newly made polypeptide is to be secreted from a cell, what must occur before it is secreted?
A. Its signal sequence must target it to the plasma membrane, where it causes exocytosis.
B. Its signal sequence must target it to the ER, after which it goes to the Golgi.
C. Its signal sequence must be cleaved off before the polypeptide can enter the ER.
D. Its signal sequence must cause it to be encased in a vesicle as soon as it is translated.
E. It must be translated by a ribosome that remains free of attachment to the ER.

B

Which of the following statements is true about protein synthesis in prokaryotes?
A. Extensive RNA processing is required before prokaryotic transcripts can be translated.
B. Unlike eukaryotes, prokaryotes require no initiation or elongation factors.
C. Translation requires antibiotic activity.
D. Translation can begin while transcription is still in progress.
E. Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles.

D

The nitrogenous base adenine is found in all members of which group?
A. proteins, triglycerides, and testosterone
B. α glucose, ATP, and DNA
C. proteins, carbohydrates, and ATP
D. proteins, ATP, and DNA
E. ATP, RNA, and DNA

E

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is
A. 3' ACU 5'.
B. 3' UCA 5'.
C. 5' TCA 3'.
D. 3' UGA 5'.
E. either UCA or TCA, depending on wobble in the first base.

B

Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression?
A. RNA polymerase binds to the promoter.
B.RNA polymerase requires a primer to elongate the molecule.
C. mRNA, tRNA, and rRNA are transcribed.
D. A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.
E. Transcription can begin as soon as translation has begun even a little.

D

Use the following model of a eukaryotic transcript to answer the question.

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'
Which of the following is a useful feature of introns for this model?
A. Introns protect exon structure.
B. Each intron has enzymatic properties.
C. Introns allow exon shuffling.
D. They are translated into small polypeptides.
E. They become parts of snRNPs.

C

Which of the following statements about ribozymes is/are correct?
Select all that apply.
A. A ribosome can be regarded as one large ribozyme.
B. Ribozymes are RNA molecules that function as enzymes.
C. In some genes, intron RNA functions as a ribozyme and catalyzes its own excision.

ABC

The following question refers to this figure of a simple metabolic pathway:
According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
0
1
2
3

2

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?
A. It uses RNA polymerase.
B. The entire template molecule is represented in the product.
C. The process occurs in the nucleus of a eukaryotic cell.
D. It makes a new molecule from its 5' end to its 3' end.
E. The process is extremely fast once it is initiated.

B

Use the following information to answer the question.
The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer.
You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible?
3
4
8
16
64

8

Which of the following nucleotide triplets best represents a codon?
A. a sequence in tRNA at the 3' end
B. a triplet separated spatially from other triplets
C. a triplet at the opposite end of tRNA from the attachment site of the amino acid
D. a triplet in the same reading frame as an upstream AUG
E. a triplet that has no corresponding amino acid

D

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by
A. a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.
B. a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes.
C. moving through a specialized channel of the nucleus.
D. a signal sequence of RNA that precedes the start codon of the message.
E. a chemical signal given off by the ER.

A

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because
A. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.
B. enzymes are made of DNA, and affected individuals lack DNA polymerase.
C. many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA.
D. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
E. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

D

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
A. shape of the A and P sites of ribosomes.
B. binding of ribosomes to mRNA.
C. bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.
D. attachment of amino acids to tRNAs.
E. bonding of the anticodon to the codon.

C

The following question refers to this table of codons.
What amino acid sequence will be generated, based on the following mRNA codon sequence?
5' AUG-UCU-UCG-UUA-UCC-UUG 3'
A. met-ser-leu-ser-leu-ser
B. met-glu-arg-arg-glu-leu
C. met-arg-glu-arg-glu-arg
D. met-leu-phe-arg-glu-glu
E. met-ser-ser-leu-ser-leu

E

What is the function of the release factor (RF)?
A. It releases the ribosome from the eR to allow polypeptides into the cytosol.
B. It separates tRNA in the A site from the growing polypeptide.
C. It binds to the stop codon in the A site in place of a tRNA.
D. It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond.
E. It supplies a source of energy for termination of translation.

C

In the 1920s, Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals-she used nitrogen mustards-have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation?
A. We want to make sure that it does not emit radiation.
B. We worry about its ability to cause infection.
C. We want to prevent any increase in mutation frequency.
D. We want to be sure that it increases the rate of mutation sufficiently.
E. We worry that it might cause mutation in cereal grain plants.

C

The flow of information in a cell proceeds in what sequence?
A. from DNA to protein to RNA
B. from RNA to DNA to protein
C. from DNA to RNA to protein
D. from protein to RNA to DNA
E. from RNA to protein to DNA

C

RNA polymerase moves in which direction along the DNA?
A. 5' to 3' along the double-stranded DNA
B. 3' to 5' along the nontemplate strand
C. 5' to 3' along the template strand
D. 5' to 3' along whichever strand it's on
E. 3' to 5' along the template strand

E

Use the following model of a eukaryotic transcript to answer the question.
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'
Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might result?
A. The 3' UTR will duplicate and one copy will replace the 5' end.
B. Removal of the 5' UTR will result in the strand not binding to tRNAs.
C. Removal of the 5' UTR also removes the 5' cap and the mRNA will quickly degrade.
D. Removal of the 5' UTR has no effect because the exons are still maintained.
E. The first exon will not be read because I1 will now serve as the UTR.

C

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
A. the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons.
B. none of the options will occur; the cell will recognize the error and destroy the tRNA.
C. proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
D. the ribosome will skip a codon every time a UUU is encountered.
E. none of the proteins in the cell will contain phenylalanine.

C

The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact?
A. Each amino acid in a protein is encoded by a triplet of nucleotides.
B. Many genes are subject to alternative RNA splicing.
C. Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.

C

Which of the following mutations would likely be most dangerous to a cell?
A. Deletion of one nucleotide
B. Substitution of one nucleotide for another
C. Deletion of three nucleotides

A

The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following?
A. polypeptide factors plus GTP
B. polypeptide factors plus ATP
C. polymerases plus GTP
D. signal peptides plus release factor
E. SRP plus chaperones

A

Using Figure 17.5 in your textbook, identify a 5' 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys.
A. 5'-CTTCGGGAA-3'
B. 5'-UUUGGGAAA-3'
C. 5'-AAACCCUUU-3'
D. 5'-GAACCCCTT-3'
E. 5'-AAAACCTTT-3'

A

Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya?
A, Transcription termination often involves attenuation.
B. Post-transcriptional splicing is like that of Eukarya.
C. Initiation of translation is like that of domain Eukarya.
D. There is only one RNA polymerase.
E. Domain Archaea have numerous transcription factors.

E

The tRNA shown in the figure has its 3' end projecting beyond its 5' end. What will occur at this 3' end?
A. The excess nucleotides (ACCA) will be cleaved off at the ribosome.
B. The small and large subunits of the ribosome will attach to it.
C. The 5' cap of the mRNA will become covalently bound.
D. The amino acid binds covalently.
E. The codon and anticodon complement one another.

D

Where does RNA polymerase begin transcribing a gene into mRNA?
A. Transfer RNA acts to translate the message to RNA polymerase.
B. It looks for the AUG start codon.
C. It starts after a certain nucleotide sequence called a promoter.
D. It starts at one end of the chromosome.
E. The ribosome directs it to the correct portion of the DNA molecule.

C

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
A. a base-pair substitution.
B. a nucleotide mismatch.
C. a polypeptide missing an amino acid.
D. a nonsense mutation.
E. a frameshift mutation.

C

A simple metabolic pathway is shown below. A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
A. an accumulation of B and no production of A and C
B. an accumulation of B and C and no production of A
C. an accumulation of C and no production of A and B
D. an accumulation of A and B and no production of C
E. an accumulation of A and no production of B and C

E

Use the following model of a eukaryotic transcript to answer the question.

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'

When the spliceosome binds to elements of this structure, where can it attach?
A. to the end of an intron
B. to the 5' UTR
C. to the 3' UTR
D. to the exons
E. to an adjacent intron and exon

A

Use the following model of a eukaryotic transcript to answer the question.

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'


Which components of the previous molecule will also be found in mRNA in the cytosol?
A. 5' UTR E1 E2 E3 E4 UTR 3'
B. 5' E1 I1 E2 I2 E3 I3 E4 3'
C. 5' UTR I1 I2 I3 UTR 3'
D. 5' I1 I2 I3 3'
E. 5' E1 E2 E3 E4 3'

A

When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply?
A. Any other regions are "junk" DNA.
B. There are also genes for RNAs other than mRNA.
C. Each gene codes for one protein.
D. The species is highly evolved.
E. There are 20,000 genes.

B

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. a deletion of two nucleotides
B. an insertion of a codon
C. a substitution of the first nucleotide of a GGG codon
D. a substitution of the third nucleotide in an ACC codon
E. a deletion of a codon

A

Which of the following provides some evidence that RNA probably evolved before DNA?
A. DNA polymerase has proofreading function.
B. RNA polymerase makes a single-stranded molecule.
C. RNA polymerase uses DNA as a template.
D. RNA polymerase does not require localized unwinding of the DNA.
E. DNA polymerase uses primer, usually made of RNA.

E

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