eukaryotic cell dicision

Question 1

what loads the two helicases onto dsDNA

Answer 1

Cdt1

Question 2

what is an A-region

Answer 2

a A-T rich consensus sequence

Question 3

features of polymerase α

Answer 3

has its own primase activity so it can make its own primers
no proof-reading 3’-5’ exonuclease

Question 4

why is polymerase α not processive

Answer 4

does not associate with PCNA

Question 5

function of replication factor C (RPC)

Answer 5

loads PCNA onto primer/DNA for a different Pol to bind to it

Question 6

role of polymerase β

Answer 6

involved in repair

Question 7

role of polymerase γ

Answer 7

replicates mtDNA

Question 8

role of polymerase δ

Answer 8

lagging strand
associates with PCNA - has proof reading

Question 9

role of polymerase ε

Answer 9

leading strand
associates with PCNA - has proof reading

Question 10

which Pols can release primers

Answer 10

Pol epsilon
Pol sigma

Question 11

what digests flaps

Answer 11

RNAse H1

Question 12

function of flap 1 endonuclease (FEN1)

Answer 12

binds PCNA and can remove any incorrect nt by cutting of a section of ssDNA/RNA

Question 13

what are telomeres

Answer 13

multiple repeats of a single sequence
TTAGGG
the last 20-200nt at the 3’ end are made of these repeats

Question 14

how can cells (cancer, embryonal etc.) bypass the Hayflick limit

Answer 14

telomerase is a ribonucleoprotein which contains a simple repeat of CUAAC
acts as a template for telomeric repeats

Question 15

how do telomeres extend

Answer 15

telomerase binds and extends ssDNA
Pol α binds and adds a primer
Pol δ binds to primer and extends it
DNA ligase fills in nicks

Question 16

how many copies of circular mtDNA per mitochondrion are there

Answer 16

2-10 copies

Question 17

what synthesis the leading strand of mtDNA and what is the lagging strand

Answer 17

Pol γ
lagging strand are RNA okazaki fragments

Question 18

what is δ replication

Answer 18

in bacteriophages - rolling circle mechanism
nick is created - acts as primer for Pol
goes around the circle constnatly replicating

Question 19

state spontaneous sources of DNA damage

Answer 19

replication errors
tautomerisation
deamination
depurination

Question 20

state induced sources of DNA damage

Answer 20

intercalating agents
base analogues
deaminating agents
alkylating agents
oxidising agents
radiation/UV

Question 21

how often does replication introduce an incorrect base and how do repair systems effect the error rate

Answer 21

10E7
10E10

Question 22

what do strand slippages cause

Answer 22

a frame shift
extra base added

Question 23

what is a tautomeric shift

Answer 23

enol group on T is converted to a a hydroxyl group
causes it to bind to G instead of A

Question 24

how does deamination affect G, A and C and what do they bind to

Answer 24

C - uracil and binds to A
A - inosine/hypoxanthine binds to C
G - xanthine binds to C (less strongly)

Question 25

which deamination can't be repaired

Answer 25

5-methyl-C to T

Question 26

what is depurination

Answer 26

cleavage of a sugar-base bond forms an abasic site

Question 27

what do intercalating agents do and cause and name one

Answer 27

insert themselves in between bases cause frame-shift mutations ethidium bromide

Question 28

name a base analogue and why they mutate DNA

Answer 28

bromouracil - T analogue incorporated into DNA more prone to tautomeric shifts

Question 29

what are alkylating agents and name one and what can it also effect seperatly

Answer 29

adds an alkyl group to the nucleobase nitrosamines/methyl bromides can speed up depurination

Question 30

what are deaminating agents and name some

Answer 30

remove amino groups nitrous acid nitrosamines nitrates/nitrites

Question 31

features of oxidising agents

Answer 31

superoxide ion (O2-) H2O2 causes most mutations many possible nucleotide alterations

Question 32

how does UV light cause mutations

Answer 32

UV-induced dimerisation of 2 adjacent thymines stops correct base-pairing in polymerase

Question 33

how does radiation, gamma/x-rays cause mutation

Answer 33

break bonds and create free-radicals ss/ds breaks bases chemically altered leading source of mutations