Chapter 6: DNA and Biotechnology

Question 1

helicase

Question 2

replisome / replication complex

Question 3

origins of replication

Question 4

replication forks

Question 5

single-stranded DNA-binding proteins

Question 6

nucleases

Question 7

supercoiling

Question 8

DNA topoisomerases

Question 9

DNA polymerase

Question 10

what direction is the NEW daughter strand synthesized?

Question 11

what direction is the parental strand read?

Question 12

leading strand

Question 13

lagging strand

Question 14

Okazaki fragments

Question 15

RNA primer

Answer 15

a short RNA sequence required to start replication

Question 16

primase

Answer 16

synthesizes the short RNA primers

Question 17

DNA polymerase I (prokaryotes) or RNase H (eukaryotes)

Answer 17

removes the RNA primer

Question 18

DNA polymerase I (prokaryotes) or DNA polymerase δ (delta, eukaryotes)

Answer 18

adds DNA nucleotides where the RNA primer had been

Question 19

DNA ligase

Answer 19

seals nicks in DNA backbone

Question 20

DNA polymerase gamma (γ)

Answer 20

replicates mitochondrial DNA

Question 21

DNA polymerase α, δ, and ε

Answer 21

synthesize the leading and lagging strands

DNA polymerase δ also fills in the gaps when the RNA primers are removed

Question 22

DNA polymerase β and ε

Answer 22

important in DNA repair

Question 23

cancer cells

Question 24

metastasis

Question 25

oncogenes

Answer 25

mutated genes that cause cancer primarily encode cell cycle related genes

Question 26

antioncogenes

Answer 26

tumor supressor genes encode proteins that inhibit the cell cycle or participate in DNA repair processes

Question 27

DNA proof reading

Question 28

which strand is more heavily methylated (template or new)?

Answer 28

template

Question 29

why are mutations more likely in the lagging strand than the reading strand?

Answer 29

DNA ligase, which closes the gaps between Okazaki fragments, lacks proofreading ability

Question 30

DNA methylation

Answer 30

a biochemical process where a DNA base (usually cytosine) is enzymatically methylated at the 5-carbon position

Question 31

mismatch repair

Answer 31

G2 phase of the cell cycle enzymes (MSH2 and MLH1) detect and remove error introduced in replication that were missed during S phase

Question 32

nucleotide excision repair

Answer 32

1. proteins scan the DNA and recognize a lesion due to a **bulge in the strand** 2. **excision endonucleases** makes a nick in the phosphodiester backbone of the damaged strand and removes the defective oligonucleotide 3. **DNA polymerase** fills in the gap by synthesizing new DNA, using the undamaged strand as a template 4. the nick is sealed by **DNA ligase**

Question 33

cytosine deamination

Answer 33

the loss of an amino group from cytosine converts cytosine to uracil

Question 34

base excision repair

Answer 34

1. the affected base is recognized an removed by a glycosylase enzyme, leaving behind an apurinic/apyrimidinic or abasic site 2. AP endonuclease recognizes the AP site and removes the damaged sequence 3. DNA polymerase fills the gap 4. DNA ligase seals the DNA strand

Question 35

what is the structural difference between the lesions corrected by nucleotide excision repair vs base excision repair?

Answer 35

nucleotide excision repair: corrects lesson which are large enough to distort the double helix (cause bulk) nucleotide excision repair: corrects lesson which are small enough to not distort the double helix (no bulk)

Question 36

recombinant DNA technology

Answer 36

allows a DNA fragment from any source to be multiplied by either gene cloning or PCR for genes to be analyzed and altered