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Genetics > Exam 2: DNA & Replication > Flashcards

Exam 2: DNA & Replication Flashcards

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Biology 101 flashcards
1
Q

3 parts of a nucleotide

A

sugar

phosphate

nitrogenous base

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2
Q

complementary base pairs

A

A—T with 2 bonds

G—C with 3 bonds

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3
Q

what is needed to make dsDNA

A

antiparallel strands with complementary base pairs

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4
Q

what stabilizes dsDNA

A

Mg2+ ions

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5
Q

Watson-Crick Model

A 
2 antiparallel strands
right-handed double helix
phosphate backbones on the outside
h-bonding from the bases on the inside
complementary pairs
Mg2+ ions to stabilize helix backbone
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6
Q

in vitro

A

in glass (test tube)

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7
Q

in vivo

A

in life

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8
Q

DNA replication in vitro is a ____

A

cell free system

you only use chemicals

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9
Q

5 things needed for in vitro DNA replication

A

DNA nucleotides in triphosphate form

a ssDNA template strand

a DNA primer

DNA polymerase enzyme

Mg2+ ions

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10
Q

what happens in in vitro DNA replication

A

DNA polymerase binds at the 3’ end of the primer

DNA polymerase extends the primer from 3’ to 5’

5’—3’(primer)-DNA polymerase—»
3’———–template——————–5’

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11
Q

what yields E for synthesis?

A

2 phosphates from the triphosphate nucleotides are lost in synthesis

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12
Q

Mg 2+

A

2 ions involved in each nucleotide addition (stabilization)

a cofactor of DNA polymerase

neutralizes charge repulsion of oxygens in DNA backbone

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13
Q

complications of in vivo DNA replication in E. coli

A

2 strands are wrapped around eachother and have to separate and replicate in opposite directions

unwinding can cause supercoiling

there is no primer when the two strands open up and separate

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14
Q

how many forks does in vivo DNA replication have?

A

two forks going in opposite directions at the same time

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15
Q

is there a primer in natural DNA replication?

A

no, there is a temporary short primer made of RNA

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16
Q

primase

A

an enzyme that makes short temporary primers from RNA

17
Q

semidiscontinuous replication

A

differences in the way synthesis occours on the leading and lagging strand

18
Q

the leading strand

A

is replicated continuously towards the fork

19
Q

the lagging strand

A

is replicated discontinuously away from the fork

20
Q

supercoil

A

when DNA unravels the strand uncoils and supercoils into loops

21
Q

supercoils on short pieces of dsDNA

A

don’t last long, they spin out

22
Q

supercoils on long linear DNA or circular DNA

A

accumulate

23
Q

should supercoils be removed?

A

yes they must in both replication and transcription

24
Q

how are supercoils removed?

A

with the enzyme topoisomerase

25
Q

topoisomerase

A

2 types (1 & 2)

enzymes that cut dsDNA either in one strand or 2 strands

26
Q

topoisomerase 1

A

cuts dsDNA on 1 strand

1) nick
2) rotate
3) ligate

27
Q

topoisomerase 2

A

cuts dsDNA on 2 strands

1) double-strand break
2) pass through
3) rejoin

28
Q

okazaki fragments

A

created during discontinuous synthesis on the lagging strand

contains an RNA primer on 5’ end and attached strand of ssDNA to 3’ end

5’-RRRRDDDD,RRRRDDDD-3’

29
Q

DNA polymerase 1

A

connects Okazaki fragments by removing RNA nucleotides one by one from right of nick

attaches DNA nucleotides to left of the nick

RRRRDDDD
D,RRRDDDD
DD,RRDDDD

30
Q

3 major differences in DNA replication in eukaryokes

A

chromosomes

packaging of DNA

rate of replication

31
Q

chromosomes in eukaryote DNA replication

A

long, linear, end in telomeres

telomerase enzyme needed to restore chromosome ends

32
Q

in eukaryotes, replication starts at…

A

replicon origins/bubbles that extend and meet each other

early and late replicating areas are organized locally into replicon families

33
Q

DNA packaging in eukaryotes

A

chromatin has nucleosome (spooled) structure

histone proteins for nucleosomes are synthesized

nucleosome cores are replicated dispersively-old and new are divided randomly into new strands

34
Q

eukaryoke DNA replication rate

A

movement of forks is slower

rate is 2000-10000 bp/min

~ 10,000 origins in mammalian genome

300,000 bp/replicon

35
Q

what end does the primer go on?

A

3’

36
Q

semiconservative replication

A

in every dsDNA one strand is the parent of the other

37
Q

ori

A

single origin of replication in circular chromosome of a bacterium like E. coli

38
Q

where on E. coli does replication begin and end

A

begins at ori and ends on other side of circular chromosome where the forks meet

Genetics (33 decks)

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