Lecture 6

Question 1

cell cycle stages

Answer 1

M > G_1 > S > G_2

Question 2

G_1

Answer 2

gap phase. rapid growth and metabolic activity. longest phase.

Question 3

cell cycle phase of DNA synthesis

Answer 3

S phase

Question 4

G_2

Answer 4

short phase. growth and preparation for division

Question 5

eukaryotic DNA polymerase alpha

Answer 5

Polymerase activity, Primase activity. leading/lagging strand synthesis. Repair.

Question 6

eukaryotic DNA polymerase beta

Answer 6

polymerase activity. repair.

Question 7

eukaryotic DNA polymerase gamma

Answer 7

polymerase activity, 3to5 exonuclease (proofreading), located in mitochondria, mitochondrial dna replication and repair.

Question 8

eukaryotic DNA polymerase delta

Answer 8

polymerase. 3to5 exonuclease (proofreading), lagging strand synthesis. repair.

Question 9

eukaryotic DNA polymerase epsilon

Answer 9

polymerase. 3to5 exonuclease (proofreading), 5to3 exonuclease, leading strand synthesis. repair.

Question 10

functions of other dna polymerases

Answer 10

bypass repair and bypass synthesis

Question 11

how is eukaryotic replication different

Answer 11

multiple origins of replication. chromatin is disrupted and reassembled. special mechanism for replicating tips.

Question 12

acetylation of chromatin histone tails

Answer 12

deacetylated in closed chromatin = inactive replication.

Question 13

eukaryotic replication initiation sequence of events

Answer 13

ORC on ORI, Cdc6 and Cdt1 bind ORC, Cdc45 and Sid3 bind ORC, Cdc6 loads Cdc45 onto DNA, Cdc6 eliminated, MCM (helicase) onto DNA which unwinds DNA, Ddc45 recruits polymerase alpha to initiate S phase, S-CDK and DDK are kinases that phosphorylate ORC proteins and trigger initiation

Question 14

eukaryotic replication scheme

Answer 14

helicase unwinds, RFA proteins decorate strands, Pol alpha (primase) binds ends of open complex, pol alpha synthesizes rna primers (10 nts), pol alpha synthesizes DNA (~15 nts), pol epsilon replaces pol alpha, polymerase switching involving RFC, pol delta and PCNA

Question 15

removal or rna primers

Answer 15

RNase H1 (endonuclease) removes most of primer, FEN1/RTHI (endo and exonuclease) removes remainder

Question 16

solution to tip replication problem

Answer 16

telomerase.

Question 17

telomerase mechanism

Answer 17

binds 3’ end of ss DNA region, 3’ end of DNA is extended using telomerase as template, telmoerase shifts to add an additional six nt repeat. …repeat

Question 18

post telomerase replication

Answer 18

pol alpha binds to make rna primer followed by short DNA sequence, RFC displaces pol alpha and place PCNA onto DNA. Pol delta binds to RFC and PCNA and fills in missing DNA, ligase connects dna, nucleases remove primer.. still 3’ overhang!

Question 19

eukaryotic replication initiation sequence of events

Answer 19

sufficient telomerase in cancer, germ, adult, and early embryonic cells. insufficient in non-germline (death of cell line after 20-60 generations)

Question 20

Adult progeria (werner’s syndrome)

Answer 20

helicase associated. mutation in WRN gene (chrom. 8). autosomal recessive, premature aging. free from alzheimers and HBP.

Question 21

WRN gene

Answer 21

3to5 dna helicase and 3to5 exonuclease, interacts with pol delta, interacts with Ku (involved in ds break repair)

Question 22

Bloom’s syndrome

Answer 22

mutation in BLM gene (chrom. 15), 3to5 DNA helicase activity, part of BRCA1 supercomplex involved in DNA damage repair