14: DNA Structure and Function

Question 1

technique used to separate DNA fragments according to size

Answer 1

electrophoresis

Question 2

during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds

Answer 2

helicase

Question 3

mutation that results from exposure to chemicals or environmental agents

Answer 3

induced mutation

Question 4

during replication, the strand that is replicated in short fragments and away from the replication fork

Answer 4

lagging strand

Question 5

strand that is synthesized continuously in the 5’-3’ direction, which is synthesized in the direction of the replication fork

Answer 5

leading strand

Question 6

enzyme that catalyzes the formation of a phosphodiester linkage between the 3’ OH and 5’ phosphate ends of the DNA

Answer 6

ligase

Question 7

type of repair mechanism in which mismatched bases are removed after replication

Answer 7

mismatch repair

Question 8

variation in the nucleotide sequence of a genome

Answer 8

mutation

Question 9

type of DNA repair mechanism in which the wrong base, along with a few nucleotides upstream or downstream, are removed

Answer 9

nucleotide excision repair

Question 10

DNA fragment that is synthesized in short stretches on the lagging strand

Answer 10

Okazaki fragment

Question 11

mutation that affects a single base

Answer 11

point mutation

Question 12

enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand

Answer 12

primase

Question 13

short stretch of nucleotides that is required to initiate replication; in the case of replication, the primer

Answer 13

primer

Question 14

function of DNA pol in which it reads the newly added base before adding the next one

Answer 14

proofreading

Question 15

Y-shaped structure formed during initiation of replication

Answer 15

replication fork

Question 16

mutation that is not expressed

Answer 16

silent mutation

Question 17

during replication, protein that binds to the single-stranded DNA; this helps in keeping the two strands of DNA apart so that they may serve as templates

Answer 17

single-strand binding protein

Question 18

ring-shaped protein that holds the DNA pol on the DNA strand

Answer 18

sliding clamp

Question 19

mutation that takes place in the cells as a result of chemical reactions taking place naturally without exposure to any external agent

Answer 19

spontaneous mutation

Question 20

enzyme that contains a catalytic part and an inbuilt RNA template; it functions to maintain telomeres at chromosome ends

Answer 20

telomerase

Question 21

DNA at the end of linear chromosomes

Answer 21

telomere

Question 22

enzyme that causes underwinding or overwinding of DNA when DNA replication is taking place

Answer 22

topoisomerase

Question 23

process in which external DNA is taken up by a cell

Answer 23

transformation

Question 24

when a purine is replaced with a purine or a pyrimidine is replaced with another pyrimidine

Answer 24

transition substitution

Question 25

when a purine is replaced by a pyrimidine or a pyrimidine is replaced by a purine

Answer 25

transversion substitution