Chapter 6

Question 1

new DNA strands contain a ____ strand and a ____ strand

Answer 1

parent
daughter

Question 2

the process of DNA synthesis is begun by ______

Answer 2

initiator proteins that bind to specific replication origins

Question 3

____ base pair is held together by fewer hydrogen bonds than a ____ base pair

Answer 3

A-T
G-C

Question 4

replication fork

Answer 4

Y-shaped junction at the site where DNA is being replicated

Question 5

DNA polymerase

Answer 5

enzyme that catalyzes the synthesis of a DNA molecule from a DNA template using deoxyribonucleoside triphosphate precursors

Question 6

DNA is synthesized in the ___ to ____ direction but read in the ____ to _____ direction

Answer 6

5’ to 3’
3’ to 5’ (how DNA polymerase moves)

Question 7

Okazaki fragment

Answer 7

short length of DNA, including an RNA primer, produced on the lagging strand during DNA replication

Question 8

lagging strand

Answer 8

DNA strand that is made discontinuously in short fragments that are later joined together to form one continuous new strand

Question 9

leading strand

Answer 9

the DNA strand that is made by continuous synthesis in the 5’ to 3’ direction

Question 10

DNA polymerase will _____ the previously added nucleotide

Answer 10

proofread/check

Question 11

primase

Answer 11

RNA polymerase that uses DNA as a template to produce a short RNA fragments that serves as a primer for DNA synthesis

Question 12

DNA ligase

Answer 12

enzyme that seals nicks that arise in the phosphodiester backbone of a DNA molecule
joins the 5’-phosphate end to the adjacent 3’-hydroxyl end

Question 13

primase ______ proofread its work

Answer 13

does not

Question 14

DNA helicase

Answer 14

enzyme that pries open the DNA double helix, using energy derived from ATP hydrolysis

Question 15

DNA topoisomerases

Answer 15

uncoils the double helix

Question 16

sliding clamp

Answer 16

keeps DNA polymerase firmly attached to the template while it is synthesizing new strands of DNA

Question 17

clamp loader

Answer 17

hydrolyzes ATP each time it locks a sliding clamp around a newly formed DNA double helix

Question 18

telomere

Answer 18

repetitive nucleotide sequence that caps the ends of linear chromosomes
counteracts the tendency of the chromosome to otherwise shorten with each round of replication

Question 19

telomerase

Answer 19

enzyme that elongates telomeres, synthesizing the repetitive nucleotide sequences found at the ends of eukaryotic chromosomes

Question 20

Which statement describes the DNA in the resulting daughter cells?
-one daughter cell receives the DNA strands that were originally in the parent cell, while the other daughter receives the newly synthesized strand
-each strand of DNA in the daughter cells contains a mix of both newly replicated and parent DNA
-the daughter cells receive only newly synthesized DNA; the parent cell keeps the original DNA
-the double helix in each daughter cell consists of one parent strand and one newly synthesized strand

Answer 20

the double helix in each daughter cell consists of one parent and one newly synthesized strand

Question 21

3 steps to repair damaged DNA

Answer 21

1. damaged DNA is recognized and removed by a variety of nucleases
2. repair DNA polymerase I binds to the 3’-hydroxyl end and fills the gap in the 5’ to 3’ direction
3. DNA ligase seals the break in the sugar-phosphate backbone

Question 22

mismatch repair

Answer 22

mechanism for recognizing and correcting incorrectly paired nucleotides-those that are noncomplementary

Question 23

nonhomologous end joining

Answer 23

error-prone mechanism for repairing double-strand breaks in DNA by rejoining the two broken ends
often results in a loss of information at the site of repair

Question 24

homologous recombination

Answer 24

mechanism by which double-strand breaks in a DNA molecule can be repaired flawlessly
uses an undamaged, duplicated, or homologous to guide the repair

Question 25

When is homologous recombination most likely to occur? -before DNA is replicated, to avoid propagating the error -when the breaks are overlooked by the fast-acting mismatch repair system -whenever a double-strand break is detected -after the cell's DNA has been replicated

Answer 25

after the cell's DNA has been replicated

Question 26

DNA mismatch repair typically corrects what percentage of replication errors?

Answer 26

99%

Question 27

Which of the following best defines a mutation? -mistake created by a faulty mismatch repair -harmful change in a DNA sequence -change in DNA sequence that causes a change in an amino acid in a protein -permanent change in a DNA sequence

Answer 27

permanent change in a DNA sequence