DNA Replication

Question 1

Replisome

Answer 1

ORI (AT rich), DnaA recognizes and induces meltiing of AT pairs using ATP, Two replication forks, catalyzed by DNA helicase within pre-priming complex (uses ATP to force strands apart), SSB proteins keep strands apart and protect from degradation, bi directional synthesis, TopII stays in from to relieve tension

Question 2

DnaA

Answer 2

Recognzizes and induces melting of AT pairs using ATP

Question 3

SSB protein

Answer 3

keeps strands apart and protects from degradation

Question 4

Helicase within prepriming complex

Answer 4

uses ATP to force strands apart

Question 5

TopII

Answer 5

relieves tension in front of rep fork, removes positive supercoils

Question 6

RNA primers

Answer 6

Primase (RNA pol) synthesize short strands of RNA in 5’ to 3’ direction, provide free 3’OH as acceptor for first nucleotide, good for lagging strand synthesis (some in leading too)

Question 7

DNA synthesis

Answer 7

DNA poly complates template strand, deoxyribonucs are precursors, new strand is anti-parallel to other strand

Question 8

Which way is dna synthesis

Answer 8

New strand is 5’ to 3’

Question 9

Leading vs lagging strand

Answer 9

leading-contrinous in 5’ to 3’ towards fork

Lagging-discontinuously, short okazaki fragments, 5’ to 3’ away from fork

Question 10

Chain Elongation

Answer 10

DNA pol III + nucleophilic attack on 3’OH terminus by phosphate group- kicks off OH

Question 11

DNA pol III

Answer 11

initiates chain elongation/exonuclease proofreading activity (3’ to 5’)

Question 12

DNA rep euk vs prok

Answer 12

More DNA, histones, telomerers, multiple origins of replication

Question 13

3 Euk polymerases

Answer 13

alpha-DNA rep (primer synthesis), initiates synthesis on leadiga nd lagging DNA strand, no exonuclease activty (similar to primase in proks)

delta-lagging strand, associate with PCNA, 3’ to 5’ exonuclease activity, displaces 5’ end of primers which are degraded by FEN1 and other exonuclease, MMR, NER

epsilon-Leading strand, associates with PCNA, 3’ to 5’ exonuclease activity, MMR, NER, if doesn’t work delta can be used

Question 14

PCNA

Answer 14

Processivity factor-allows efficient movement along DNA

Question 15

Nuceleosomes

Answer 15

Remain lightly bound to parental DNA, New histones being formed on novel strand, reforms behind advancing rep fork

Question 16

Telomeres

Answer 16

Protect from degradation and protect important DNA from being lost (DNA lost from end of linear chromosomes when primers are removed)

Question 17

Telomerase

Answer 17

Ribonucleoide protein (RNA and protein), adds short G-rich DNA repeats to single stranded 3’ ends of linear chromosomes, RNA part synthesizes telomeric repeats-synthesizes DNA from RNA primer), protein part has reverse transcriptase activity,

Question 18

how does telomerase do job

Answer 18

bind to parents strand downstream (no nascent strand at this point), start synthesizing in 3’ to 5’ direction (regarding nascent strand), moves over and does it again, then DNA poly fills in gap between initial new telomere part and normally synthesized DNA

Question 19

DNA rep with/without telomeres

Answer 19

Without-lose DNA when RNA primer is removed

With-Lose telemeric repeat when primer is removed

Question 20

T loops

Answer 20

Telomeric repeat loops that protect DNA from degradation/combining

Question 21

Telomerase activity

Answer 21

Active all the time in germ cells/Stem cells/fetal cells/Sometimes in cells that divide rapidly
Inactive in somatic cells
Re-activation can cause cancer

Question 22

DNA damage sensor

Answer 22

Recognizes when DNA is so unfunctional that cell most be killed