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BioChemistry > Replication in Eukaryotes > Flashcards

Replication in Eukaryotes Flashcards

1
Q

Replication in eukaryotes are ____ and _____ than prokaryotes

A

slower and higher accuracy

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2
Q

DNA polymerase alpha function

A

forms a complex with primase and this complex makes RNA primer and Short DNA

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3
Q

DNA polymerase alpha + primase

A

DNA polymerase alpha primase complex

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4
Q

DNA polymerase beta function

A

DNA repair

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5
Q

DNA polymerase y (gamma) function

A

Replicated mitochondrial DNA

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6
Q

Steps of replication in eukaryotes

A
  1. Separation of strands and formation of prepriming complex
  2. Initation of DNA Synthesis: Formation of RNA Primers
  3. Elongation
  4. Termination
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7
Q

Steps of replication in eukaryotes- Separation of Strands and Formation of Prepriming Complex

A
  • Occurs at multiple origins of replication (Origin-C) = Multiple Replication Forks = Faster Replication
  • Unwinding of strands are by DNA Helicase
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8
Q

Ori C is rich in

A

AT base pairs

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9
Q

How are the 2 strands kept separated in replication?

A

by single stranded binding protein

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10
Q

Steps of replication in eukaryotes- Initiation of DNA Synthesis

A

Formation of RNA primers

DNA polymerase alpha primase complex forms RNA primer and short stretch of DNA (15-30 nucleotides)

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11
Q

Steps of replication in eukaryotes - Elongation

A

DNA polymerase epsilon (3) : Replicates Leading Strand

DNA polymerase delta (s) : Replicates Lagging Strand

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12
Q

Steps of replication in eukaryotes- Termination

A

RNase H removes RNA Primers
DNA polymerase delta (s) fill the gaps
DNA Ligase seals the nicks

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13
Q

Solving the problem of supercoiling by

A

Topoisomerase 1 and 2

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14
Q

enzymes of DNA repair in eukaryotes

A

DNA polymerase b & e (beta and epsilon)

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15
Q

origin of replication in prokaryotic vs eukaryotes

A

Prokaryote- One

Eukaryotes - Multiple

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16
Q

replication fork prokaryotic vs eukaryotes

A

prokaryotic - two

eukaryotes - multiple

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17
Q

replication fork speed prokaryotic vs eukaryotes

A

prokaryotic - rapid

eukaryotes - slow

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18
Q

RNA Primer length prokaryotic vs eukaryotes

A

prokaryotic - short

eukaryotes - long

19
Q

Primer synthesis name- prokaryotic vs eukaryotes

A

prokaryotic - primase

eukaryotes- DNA polymerase alpha primase complex

20
Q

Okazaki Fragments prokaryotic vs eukaryotes

A

prokaryotic- long 1000-2000 nucleotide

eukaryotes- shorter 100-200 nucleotide

21
Q

Enzymes that synthesize leading strand- prokaryotic vs eukaryotes

A

prokaryotic - DNA polymerase 3

eukaryotes - DNA polymerase Epsilon (3)

22
Q

Enzymes that synthesize lagging strand- prokaryotic vs eukaryotes

A

prokaryotic - DNA polymerase 3

eukaryotes - DNA polymerase Delta (s)

23
Q

telomere and telomerase are in

A

eukaryotes only

24
Q

telomere

A

non coding sequence at end of chromosome and consists of variable repeats

25
Q

variable repeats of telomere

A

TTAGGG

26
Q

Problems in telomere

A
  1. Looks like chromosome break

2. Shortening of the chromosome

27
Q

How to solve telomere looking like chromosome break?

A

the 3’ end is longer than 5’ end so it folds over itself and binds to 5’ end to prevent chromosomal recombination

28
Q

explain telomere shortening of chromosome

A

problem in the lagging strand. Primase can’t work at very end of chromosome (3’ end) and the removal of RNA primer leaves a short gap.

This isn’t a problem at the beginning because it takes away from telomere but over many cycles, it would lead to chromosomal shortening and genes are lost and cells die.

29
Q

how to solve telomere shortening of chromosome

A

telomerase binds to 3’ end and adds repetitive bases of AAUCCC to elongate strand to DNA template strand. This allows the primase to work on original DNA

30
Q

telomerase

A

Ribonucleoprotein (RNA + protein) with reverse transcriptase activity (RNA -> DNA)

Contains 150 nucleotides of sequence AAUCCC

31
Q

significance of telomerase in relation to cell division

A

limited ability for division -> don’t express telomerase

rapidly dividing cells -> high telomerase activity

32
Q

significance of telomerase in relation to aging

A

aging is slight shortening of chromosomes that occur with each cycle until essential genes are ruined causing aging and death.

Cells that don’t age such as germ cells and cancer tells have high telomerase activity

33
Q

error in replication in eukaryotes intro

A

replication has high accuracy but error can occur due to exposure of chemicals or radiation during replication. If damage is not cured-> permanent mutation -> disorder

34
Q

steps of DNA repair

A
  1. recognition of lesion (problem)
  2. Endonuclease
  3. Exonuclease
  4. DNA repair enzymes
  5. Ligase
35
Q

steps of DNA repair- recognition of lesion

A

a protein scans the 2 DNA strands

36
Q

steps of DNA repair- endonuclease

A

cuts the damage strand from the middle at site of problem

37
Q

steps of DNA repair- exonuclease

A

removes mutation base -> leaves gap

38
Q

steps of DNA repair- DNA Repair enzymes

A

fills gaps with right base

39
Q

steps of DNA repair- ligase

A

seals the nick

40
Q

diseases due to defect in DNA repair

A
  1. Xeroderma Pigmentosum
  2. Ataxia Telangectasia
  3. Werner Syndrome
41
Q

diseases due to defect in DNA repair- Xeroderma Pigmentosum Cause and Symptoms

A

Dry Skin Pigment
Cause: Genetic Disease due to defect in repair
Symptoms: Very sensitive to sun light and UVL and get skin burns and ulcers. This can lead to skin cancer and death

42
Q

diseases due to defect in DNA repair- Ataxia Telangectasia Cause and Symptoms

A

Cause: Defect in enzymes of DNA Repair
Symptoms: High sensitivity to radiations like X Rays can lead to ataxia and dilated blood vessels

43
Q

diseases due to defect in DNA repair- Werner Syndrome Symptoms

A

Premature aging & retardation of growth (old face and young body)

BioChemistry (7 decks)

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