Deck 7: Replication, Maintenance, and Rearrangements of Genomic Dna

Question 1

DNA polymerases can synthesize DNA

A) de novo by catalyzing the polymerization of free dNTPs.
B) by adding dNTPs to complementary dNTPs on a single-stranded DNA.
C) by adding dNTPs to a hydroxyl group on the end of a growing polynucleotide chain hydrogen-bonded to a strand of RNA.
D) by adding dNTPs to a hydroxyl group on the end of a growing polynucleotide chain hydrogen-bonded to a strand of DNA.

Answer 1

D

Question 2

In addition to synthesizing DNA, DNA polymerase I has a second catalytic activity: it can

A) synthesize short RNA sequences.
B) synthesize short polypeptide sequences.
C) remove RNA primers.
D) ligate short segments of DNA together.

Answer 2

C

Question 3

Short segments of newly synthesized DNA on the lagging strand of DNA are called

A) Okazaki fragments.
B) replicons.
C) origins of replication.
D) lagging fragments.

Answer 3

A

Question 4

The short fragments of DNA produced during DNA replication are joined together by

A) RNA polymerase.
B) DNA polymerase.
C) DNA helicase.
D) DNA ligase.

Question 5

Which eukaryotic DNA polymerase replicates the leading strand in the 5'to 3'direction?

A) $\alpha$
B) $\gamma$
C) $\delta$
D) $\beta$

Question 6

Which eukaryotic DNA polymerase replicates the lagging strand in the 3ʹ to 5ʹ direction?

A) α
B) γ
C) δ
D) None of the above; the lagging strand is replicated in the 5ʹ to 3ʹ direction.

Question 7

Primase synthesizes short sequences of _______ complementary to the _______ strand.

A) DNA; leading
B) RNA; lagging
C) DNA; lagging
D) All of the above

Question 8

In eukaryotic cells, RNA primers are removed by the combined action of 5ʹ to 3ʹ exonucleases and

A) Rnase A.
B) RNase H.
C) DNA polymerase I.
D) DNA polymerase α.

Question 9

Eukaryotic DNA polymerase ε

A) is the polymerase for leading-strand replication.
B) is the polymerase for lagging-strand replication.
C) fills in the gaps between Okazaki fragments.
D) functions primarily in repair of DNA damage.

Question 10

In E. coli, the major enzyme responsible for DNA replication is DNA polymerase

A) $\Iota$
B) $\Iota$$\Iota$
C) $\Iota$$\Iota$$\Iota$
D) $\alpha$

Question 11

Proliferating cell nuclear antigen (PCNA) is a(n) _______ in eukaryotes.

A) DNA polymerase
B) sliding-clamp protein
C) single-stranded DNA binding protein
D) origin-of-replication binding protein

Question 12

Free rotation of one cut DNA strand around one uncut strand is the primary function of

A) topoisomerase I.
B) topoisomerase II.
C) DNA helicase.
D) DNA polymerase.

Question 13

The function of topoisomerase II is to

A) resolve DNA tangles.
B) allow DNA to swivel and unwind.
C) allow daughter chromatids to separate in anaphase.
D) All of the above

Question 14

During DNA replication, the overall error frequency is 1 in _______ base pairs.

A) 10⁵
B) 10⁶
C) 10⁸
D) 10⁹

Question 15

The proofreading property of DNA polymerase is due to its _______ activity.

A) 3ʹ to 5ʹ exonuclease
B) 5ʹ to 3ʹ exonuclease
C) excision repair
D) endonuclease

Question 16

Origins of replication are the

A) sites where DNA transcription starts.
B) binding sites for the protein complex that initiates DNA synthesis.
C) loops with two replication forks seen in replicating DNA.
D) forks where DNA replication is occurring.

Question 17

Autonomously replicating sequences are

A) yeast plasmids.
B) yeast telomeres.
C) bacterial plasmids.
D) yeast origins of replication.

Question 18

Telomeres are the

A) midpoints of chromosomes.
B) microtubule attachment points on chromosomes.
C) end-sequences of chromosomes.
D) enzyme complexes that complete DNA replication.

Question 19

Telomerase is

A) a reverse transcriptase.
B) the enzyme that adds a random sequence to the ends of chromosomes.
C) an enzyme first discovered in Thermus aquaticus.
D) An enzyme that breaks down DNA from the ends.

Question 20

Pyrimidine dimers

A) block DNA replication and transcription.
B) can be repaired by photoreactivation.
C) can be repaired by nucleotide-excision repair.
D) All of the above

Question 21

The human disease in which affected individuals are extremely sensitive to sunlight and develop multiple skin cancers on exposed areas is called

A) melanoma.
B) zero pigment disease.
C) xeroderma pigmentosum.
D) Cockayne's syndrome.

Question 22

Cultured cells from xeroderma pigmentosum patients were unable to carry out

A) base-excision repair.
B) nucleotide-excision repair.
C) synthesis of melanin.
D) DNA synthesis.

Question 23

The most common cause of skin cancer is damage to DNA by

A) infrared light.
B) ultraviolet light.
C) γ radiation.
D) β particle radiation.

Question 24

The human genes that convey a susceptibility to hereditary nonpolyposis colorectal cancer are genes coding proteins involved in the DNA repair mechanism called

A) mismatch repair.
B) nucleotide-excision repair.
C) photoreactivation.
D) transcription-coupled repair.

Question 25

Patients with hereditary nonpolyposis colorectal cancer genes should have

A) frequent colonoscopies.
B) a colectomy.
C) gene-replacement therapy.
D) an intraperitoneal injection of the normal enzyme.

Question 26

E. coli DNA polymerase V

A) is induced in response to high temperatures.
B) recognizes thymine dimers and inserts nucleotides on the opposite strand.
C) has a low frequency of errors.
D) is activated during transcription.

Question 27

Double-stranded breaks are repaired by

A) direct reversal of DNA damage.
B) translesion repair.
C) excision repair.
D) recombinational repair.

Question 28

The gene responsible for inherited breast cancer (BRCA2) encodes a protein that is involved in

A) initiation of cell death by apoptosis.
B) regulation of cell proliferation.
C) repair of double-strand DNA breaks by homologous recombination.
D) error-prone repair.

Question 29

Site-specific recombination

A) occurs in randomly occurring DNA sequences.
B) is mediated by proteins that recognize specific DNA target sequences.
C) leads to programmed cell death.
D) is also referred to as homologous recombination.

Question 30

Site-specific recombination occurs commonly during

A) mitosis of somatic cells.
B) meiosis of germ cells.
C) development of immune-system cells.
D) prokaryotic cell division.

Question 31

Recombination of DNA strands is important because it can

A) rearrange DNA sequences to change gene expression during development.
B) inactivate the repair of damaged sequences.
C) inhibit diversity in the next generation.
D) All of the above

Question 32

Which of the following regions make up a mature immunoglobulin heavy chain?

A) VDJC
B) VJC
C) VDJ
D) VDJR

Question 33

Which region is not part of the immunoglobulin light chain?

A) V region
B) J region
C) D region
D) C region

Question 34

In the mouse, the total number of heavy chains that can be generated by site-specific recombination events is about

A) 600.
B) 7,200.
C) 10⁵.
D) 10⁶.

Question 35

A major difference between immunoglobulin heavy chains and light chains is that heavy chains contain _______ regions.

A) V
B) D
C) J
D) C

Question 36

Mutations in the genes for RAG1 and RAG2 would most likely have an effect on

A) VDJ recombination in the immune system.
B) mismatch repair.
C) excision repair.
D) translesion DNA synthesis.

Question 37

T cell receptors

A) are found in the circulation.
B) contain variable and regulatory regions.
C) are tetrameric complexes that contain $\alpha$ , $\beta$ , $\gamma$ , and $\delta$ polypeptide chains.
D) bind antigens present on the surface of other cells.

Question 38

Gene amplification is

A) seen in ribosomal genes of developing amphibian oocytes.
B) seen in the genes for muscle proteins of developing muscle cells.
C) seen in the genes for immunoglobulins during B lymphocyte development.
D) never seen in eukaryotic cells, since the amount of DNA per cell is always constant, except during S phase of the cell cycle.

Question 39

A mutation in the enzyme _______ will block the separation of daughter chromatids in mitosis.

Question 40

On one typical eukaryotic chromosome there are, in number, _______ telomere(s) and _______ origin(s) of replication.

Question 41

On a typical prokaryotic chromosome the number of telomeres and origins of replication is _______ telomere(s) and _______ origin(s) of replication.

Question 42

The BRCA genes responsible for inherited breast cancer are involved in the repair of _______ DNA breaks by homologous recombination.

Question 43

Repair of double-strand breaks in DNA caused by ionizing radiation often leads to the loss of _______ around the site of damage.

Question 44

The genes that encode the immunoglobulin light chain consist of regions that are called _______, _______, and _______.

Question 45

IgM antibodies contain _______ constant regions in their heavy chains.

Question 46

T cell receptors bind to _______ on the surface of other cells during immune responses.

Question 47

T cell receptors resemble _______ in many ways.

Question 48

_______ can be beneficial to organisms such as amphibians to accommodate the generation of large pools of rRNAs, while it can be deleterious in some forms of cancer by dramatically increasing the number of genes driving proliferation.

Question 49

All known DNA polymerases synthesize DNA in the 5ʹ to 3ʹ direction.

Question 50

Mitochondria have their own unique DNA polymerase.

Question 51

Eukaryotic cells have many different DNA polymerases, one or more of which function primarily in repair of damaged DNA.

Question 52

The leading and lagging strands at a replication fork are synthesized in opposite directions, but both are synthesized in a continuous manner.

Question 53

Both topoisomerase I and topoisomerase II allow DNA to relieve torsion.

Question 54

Some DNA polymerases have a nuclease activity that allows them to remove mismatched nucleotides and repair a sequence.

Question 55

Proofreading is done by DNA polymerases.

Question 56

DNA replication starts at sites called replication forks.

Question 57

Yeast origins of replication are autonomously replicating sequences.

Question 58

The rate of DNA replication in mammalian cells is tenfold faster than in prokaryotic cells.

Question 59

Telomere sequences form loops at the ends of eukaryotic chromosomes.

Question 60

Telomerase is a reverse transcriptase.

Question 61

Telomerase carries its own template DNA.

Question 62

Telomerase extends the ends of linear chromosomes by making a copy that is complementary to the other strand of DNA.

Question 63

DNA glycosylase can give rise to apyrimidinic and apurinic sites by cleaving bases from their deoxyribose on the DNA backbone.

Question 64

DNA polymerases cannot replicate DNA across from a site of DNA damage.

Question 65

Somatic hypermutation is focused in the diversity region of the immunoglobulin gene.

Question 66

How do DNA polymerases differ from RNA polymerases in terms of primer requirement?

Question 67

Why does the synthesis of Okazaki fragments require an RNA primer?

Question 68

Why does DNA polymerase synthesize DNA only in the 5ʹ to 3ʹ direction?

Question 69

Explain how a prokaryotic chromosome can replicate and divide normally with no telomeres and only one origin of replication.

Question 70

What are the functions of origins of replication?

Question 71

What are the functions of telomeres?

Question 72

Why is telomerase important in cancer cells?

Question 73

What type of DNA damage would you expect to occur more frequently in populations as they near the equator?

Question 74

Explain Tonegawa's key conclusion about the development of immunoglobulin genes.

Question 75

In E. coli, the major enzyme responsible for DNA replication is DNA polymerase

A) I.
B) II.
C) III.
D) $\alpha$ .

Question 76

Which statement is true of all known DNA polymerases?

A) They synthesize DNA in the 5ʹ to 3ʹ direction, and they require a preformed primer hydrogen-bonded to the template.
B) They synthesize DNA in the 5ʹ to 3ʹ direction, and they possess primase activity.
C) They require a preformed primer, and they possess helicase activity.
D) They synthesize DNA in the 3ʹ to 5ʹ direction, and they possess exonuclease activity.

Question 77

DNA polymerase requires a primer and cannot initiate synthesis de novo. What serves as a primer for DNA replication?

A) Short fragments of DNA complementary to the template strand
B) A protein with a free OH group
C) Short fragments of RNA complementary to the template strand
D) Double-stranded hairpins at the end of the DNA molecule that are formed by a looping of the DNA

Question 78

Which statement concerning elongation of DNA at the replication fork is false?

A) The leading strand is synthesized continuously in the direction of replication fork movement.
B) The lagging strand is synthesized in Okazaki fragments backward from the overall direction of replication.
C) The Okazaki fragments are joined by the action of DNA ligase.
D) Both strands are synthesized continuously at the replication fork.

Question 79

The twisting of the parental DNA strands around each other ahead of a replication fork is relieved by enzymes called

A) DNA helicases.
B) topoisomerases.
C) DNA ligases.
D) DNA polymerases.

Question 80

During replication, _______ stabilize the unwound DNA template so it can be copied by the DNA polymerase.

A) Single-stranded DNA-binding proteins
B) Helicases
C) PCNAs
D) Topoisomerases