Deck 15: Dna and the Gene: Synthesis and Repair

Question 1

Who performed the classic experiments that proved DNA was copied by semiconservative replication?

A) Meselson and Stahl
B) Hershey and Chase
C) Watson and Crick
D) Franklin and Wilkins

Answer 1

A

Question 2

What is the difference between the leading strand and the lagging strand in DNA replication?

A) The leading strand is synthesized in the 3'-5' direction in a discontinuous fashion, while the lagging strand is synthesized in the 5'-3' direction in a continuous fashion.
B) The leading strand is synthesized continuously in the 5'-3' direction, while the lagging strand is synthesized discontinuously in the 5'-3' direction.
C) The leading strand requires an RNA primer, whereas the lagging strand does not.
D) There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.

Answer 2

B

Question 3

What provides the energy for the polymerization reactions in DNA synthesis?

A) breaking the hydrogen bonds between complementary DNA strands
B) ATP
C) DNA polymerase
D) the deoxyribonucleotide triphosphate substrates

Answer 3

D

Question 4

Put the following steps of DNA replication in chronological order.
1) Single- stranded binding proteins attach to DNA strands.
2) Hydrogen bonds between base pairs of antiparallel strands are broken.
3) Primase binds to the site of origin.
4) DNA polymerase binds to the template strand.
5) An RNA primer is created.

A) 3, 2, 1, 5, 4
B) 1, 2, 3, 4, 4
C) 2, 1, 3, 5, 4
D) 1, 2, 3, 4, 5

Question 5

DNA is synthesized through a process known as

A) conservative replication.
B) dispersive replication.
C) semiconservative replication.
D) transcription.

Question 6

In Figure 15.2, which is the template strand?

A) a
B) b
C) c
D) d

Question 7

Watson and Crick elucidated the structure of DNA in 1953. Their research built on and helped explain the findings of other scientists, including

A) Scientists who recognized that a nucleotide consisted of a sugar, a phosphate, and a nitrogen- containing base.
B) X- ray diffraction studies by Rosalind Franklin and Maurice Wilkins.
C) Chargaff's rules: C = G and T = A.
D) All of the above were important considerations in the elucidation of the structure of DNA.

Question 8

Figure 15.3

-Refer to Figure 15.3. Which of the structures in the figure breaks hydrogen bonds between complementary bases?

Question 9

Semiconservative replication involves a template. What is the template?

A) an RNA molecule
B) one strand of the DNA molecule
C) DNA polymerase contains the template needed
D) single- stranded binding proteins

Question 10

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.

A) a nitrogen from the nitrogen- containing base
B) C₆
C) the 3' OH
D) ATP

Question 11

At a specific area of a chromosome, the following sequence of nucleotides is present where the chain opens to fo 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'

Question 12

Figure 15.2
Identify the lagging strand in Figure 15.2.

A) a
B) b
C) c
D) d

Question 13

What can you infer from the information presented in this table?

A) DNA polymerase I and DNA polymerase III have different functions.
B) The sliding clamp molecule is a ribozyme.
C) DNA polymerase I and DNA polymerase III are the same enzyme found in different organisms.
D) Topoisomerase is involved in proofreading activity.

Question 14

The transduction experiments done by Hershey and Chase, and the transformation experiments done by Griffith, supported the same conclusion, which was that

A) genetic recombination in living organisms is rare.
B) organisms must be sacrificed for science to progress.
C) pathogenic molecules affect the health of all living organisms.
D) DNA is the molecular substance of genetic inheritance.

Question 15

The fact that within a double- stranded DNA molecule, adenine forms two hydrogen bonds with thymine and cytosine forms three hydrogen bonds with guanine is known as

A) a double helix.
B) complementary base pairing.
C) semi- conservative replication.
D) secondary structure of a DNA molecule.

Question 16

How does the simple primary and secondary structure of DNA hold the information needed to code for the many features of multicellular organisms?

A) The hydrogen bonding among backbone constituents carries coded information.
B) The base sequence of DNA carries all the information needed to code for proteins.
C) The amino acids that make up the DNA molecule contain the information needed to make cellular proteins.
D) The covalent bonding among backbone constituents contains the information that is passed from generation to generation.

Question 17

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

A) DNA polymerases of prokaryotes can add nucleotides to both 3' and 5' ends of DNA strands, while those of eukaryotes function only in the 5'-3' direction.
B) DNA polymerase III of eukaryotes has both endonuclease and exonuclease activity, while that of prokaryotes has only exonuclease activity.
C) Prokaryotic replication does not require a primer.
D) Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

Question 18

$\text {Single strand as a template plus \(3 ^ { \prime }\) end to }$
$\text {start DNA synthesis}$


Figure 15.1

-Refer to Figure 15.1. What bases will be added to the primer as DNA replication proceeds? The bases should appear in the order that they will be added.

A) A, G, A, C, G, A, C
B) T, C, T, G, C, T, G
C) C, A, G, C, A, G, A
D) U, G, U, C, G, U, C

Question 19

Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of transduction experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?

A) DNA
B) lipid
C) protein
D) carbohydrate

Question 20

Figure 15.3

-Refer to Figure 15.3. Which structure is responsible for stabilizing DNA in its single- stranded form?

Question 21

In the mismatch repair process, enzyme complexes replace bases that were incorrectly inserted into the newly synthesized DNA strand. To function, they must be able to distinguish between the parent DNA strand and the new strand. How is this accomplished?

A) The new strand contains ribose sugars.
B) The parent strand is methylated.
C) The new strand contains the diphosphate bases.
D) The parent strand is usually radiolabeled.

Question 22

What are thymine dimers?

A) pyrimidines C and T) that have gained an extra nitrogen- containing ring structure
B) thymines on antiparallel DNA strands that form complementary base pairs
C) thymines formed by demethylation of purines
D) adjacent thymines on the same DNA strand that join by covalent bonding

Question 23

Telomere shortening is a problem in which types of cells?

A) prokaryotes
B) eukaryotes
C) both prokaryotes and eukaryotes

Question 24

Which one of the following is least likely to cause mutations in DNA?

A) ultraviolet radiation from sunlight
B) aflatoxins that are found in mouldy grains
C) hydroxyl radicals formed as by- products of aerobic respiration
D) medical X- rays to detect broken bones
E) light from an incandescent bulb

Question 25

Recent studies have shown that xeroderma pigmentosum an error in the nucleotide excision repair process) can result from mutations in one of seven genes. What can you infer from this finding?

A) These mutations have resulted from translocation of gene segments.
B) These seven genes are the most easily damaged by ultraviolet light.
C) There are several enzymes involved in the nucleotide excision repair process.
D) There are seven genes that produce the same protein.

Question 26

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?

A) Telomerase shortens telomeres, which delays cellular aging.
B) Telomerase will speed up the rate of cell proliferation.
C) Telomerase would have no effect on cellular aging.
D) Telomerase would decrease the rate of DNA replication.
E) Telomerase eliminates telomere shortening and retards aging.

Question 27

Hereditary nonpolyposis colorectal cancer HNPCC) is an inherited disorder. The genetic defect identified is an error in the mismatch repair mechanism. Which of the following would be an expected result of this mutation?

A) increased rate of repair of pyrimidine dimers
B) increased rate of errors by wild- type DNA polymerase
C) decreased ability to repair certain DNA mutations
D) increased rate of formation of pyrimidine dimers

Question 28

The epsilon s) subunit of DNA polymerase III of E. coli has exonuclease activity. How does it function in the proofreading process?

A) The epsilon subunit excises a segment of DNA around the mismatched base.
B) The epsilon subunit can remove a mismatched nucleotide.
C) The epsilon subunit can recognize which strand is the template or parent strand, and which is the new strand of DNA.
D) It adds nucleotide triphosphates to the 3' end of the growing DNA strand.

Question 29

DNA replication is highly accurate. It results in about one mistake per billion nucleotides. For the human genome, how often would errors occur?

A) on average, once every 6 cell divisions
B) on average, once or twice in the lifetime of an individual
C) on average, 6 times each time the entire genome of a cell is replicated
D) on average, once a lifetime in 10% of the population

Question 30

What is a telomere?

A) the ends of linear chromosomes
B) the reorganization of the cell nucleus that takes place during telophase
C) the site of origin of DNA replication
D) the mechanism that holds two sister chromatids together

Question 31

Which of the following agents can cause mutations in DNA?

A) ultraviolet radiation from sunlight
B) aflatoxins that are found in moldy grains
C) free radicals that are formed as by- products of aerobic respiration
D) All of the above are mutagenic agents.

Question 32

If during the process of DNA replication, the enzyme topoisomerase was not functioning i.e. it was mutated) what do you expect will happen to the replication process?

A) The double helix would unwind completely but no primers would be added to the template strand.
B) The double helix would unwind completely but no new strand would be created due to the formation of secondary structures.
C) The double helix would begin to unwind but this unwinding would stop prematurely due to over- twisting of the DNA.
D) The double helix would not begin to unwind at all.

Question 33

If DNA repair mechanisms fail, what is the result?

A) cancer
B) a mutation
C) a defective enzyme
D) All of the above can result from the failure of DNA repair mechanisms.

Question 34

What appears to be a dark side to telomerase activity with regard to human health?

A) Telomerase is active in most cancer cells.
B) Telomerase activity is only seen in somatic cells; therefore, chromosome shortening is likely in gametic chromosomes.
C) Telomerase is inhibited by p53.
D) There are more chromosomal ends than can be repaired by telomerase.
E) p53 inhibits telomerase.

Question 35

Which of the following cells do not have active telomerase activity?

A) most normal somatic cells
B) most cancer cells
C) most normal germ cells

Question 36

Researchers found E. coli that had mutation rates 100 times higher than normal. What is a possible explanation for these results?

A) The proofreading mechanism of DNA polymerase was not working properly.
B) There were one or more mismatches in the RNA primer.
C) The DNA polymerase was unable to add bases to the 3' end of the growing nucleic acid chain.
D) The single- stranded binding proteins were malfunctioning.

Question 37

Bodnar et al. 1998) used telomerase to extend the life span of normal human cells. Telomere shortening puts a limit on the number of times a cell can divide. How might adding telomerase affect cellular aging?

A) Telomerase shortens telomeres and thus delays cellular aging.
B) Telomerase ensures that the ends of the chromosomes are accurately replicated and eliminates telomere shortening.
C) Telomerase will speed up the rate of cell proliferation.
D) Telomerase would have no effect on cellular aging.

Question 38

Which of the following are important in reducing the errors in DNA replication in E. coli organisms?

A) mismatch repair
B) nucleotide excision repair
C) proofreading activity of the epsilon subunit of DNA polymerase III
D) All of the above minimize errors in DNA replication in E. coli.

Question 39

Which of the following would you expect of a eukaryote lacking telomerase?

A) a high probability of somatic cells becoming cancerous
B) high sensitivity to sunlight
C) a reduction in chromosome length in gametes
D) an inability to produce Okazaki fragments
E) an inability to repair thymine dimers