Replication in Eukaryotes

Question 1

Replication in eukaryotes are ____ and _____ than prokaryotes

Answer 1

slower and higher accuracy

Question 2

DNA polymerase alpha function

Answer 2

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

Question 3

DNA polymerase alpha + primase

Answer 3

DNA polymerase alpha primase complex

Question 4

DNA polymerase beta function

Answer 4

DNA repair

Question 5

DNA polymerase y (gamma) function

Answer 5

Replicated mitochondrial DNA

Question 6

Steps of replication in eukaryotes

Answer 6

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

Question 7

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

Answer 7

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

Question 8

Ori C is rich in

Answer 8

AT base pairs

Question 9

How are the 2 strands kept separated in replication?

Answer 9

by single stranded binding protein

Question 10

Steps of replication in eukaryotes- Initiation of DNA Synthesis

Answer 10

Formation of RNA primers

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

Question 11

Steps of replication in eukaryotes - Elongation

Answer 11

DNA polymerase epsilon (3) : Replicates Leading Strand

DNA polymerase delta (s) : Replicates Lagging Strand

Question 12

Steps of replication in eukaryotes- Termination

Answer 12

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

Question 13

Solving the problem of supercoiling by

Answer 13

Topoisomerase 1 and 2

Question 14

enzymes of DNA repair in eukaryotes

Answer 14

DNA polymerase b & e (beta and epsilon)

Question 15

origin of replication in prokaryotic vs eukaryotes

Answer 15

Prokaryote- One

Eukaryotes - Multiple

Question 16

replication fork prokaryotic vs eukaryotes

Answer 16

prokaryotic - two

eukaryotes - multiple

Question 17

replication fork speed prokaryotic vs eukaryotes

Answer 17

prokaryotic - rapid

eukaryotes - slow

Question 18

RNA Primer length prokaryotic vs eukaryotes

Answer 18

prokaryotic - short

eukaryotes - long

Question 19

Primer synthesis name- prokaryotic vs eukaryotes

Answer 19

prokaryotic - primase

eukaryotes- DNA polymerase alpha primase complex

Question 20

Okazaki Fragments prokaryotic vs eukaryotes

Answer 20

prokaryotic- long 1000-2000 nucleotide

eukaryotes- shorter 100-200 nucleotide

Question 21

Enzymes that synthesize leading strand- prokaryotic vs eukaryotes

Answer 21

prokaryotic - DNA polymerase 3

eukaryotes - DNA polymerase Epsilon (3)

Question 22

Enzymes that synthesize lagging strand- prokaryotic vs eukaryotes

Answer 22

prokaryotic - DNA polymerase 3

eukaryotes - DNA polymerase Delta (s)

Question 23

telomere and telomerase are in

Answer 23

eukaryotes only

Question 24

telomere

Answer 24

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

Question 25

variable repeats of telomere

Answer 25

TTAGGG

Question 26

Problems in telomere

Answer 26

1. Looks like chromosome break | 2. Shortening of the chromosome

Question 27

How to solve telomere looking like chromosome break?

Answer 27

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

Question 28

explain telomere shortening of chromosome

Answer 28

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.

Question 29

how to solve telomere shortening of chromosome

Answer 29

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

Question 30

telomerase

Answer 30

Ribonucleoprotein (RNA + protein) with reverse transcriptase activity (RNA -> DNA) Contains 150 nucleotides of sequence AAUCCC

Question 31

significance of telomerase in relation to cell division

Answer 31

limited ability for division -> don't express telomerase | rapidly dividing cells -> high telomerase activity

Question 32

significance of telomerase in relation to aging

Answer 32

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

Question 33

error in replication in eukaryotes intro

Answer 33

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

Question 34

steps of DNA repair

Answer 34

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

Question 35

steps of DNA repair- recognition of lesion

Answer 35

a protein scans the 2 DNA strands

Question 36

steps of DNA repair- endonuclease

Answer 36

cuts the damage strand from the middle at site of problem

Question 37

steps of DNA repair- exonuclease

Answer 37

removes mutation base -> leaves gap

Question 38

steps of DNA repair- DNA Repair enzymes

Answer 38

fills gaps with right base

Question 39

steps of DNA repair- ligase

Answer 39

seals the nick

Question 40

diseases due to defect in DNA repair

Answer 40

1. Xeroderma Pigmentosum 2. Ataxia Telangectasia 3. Werner Syndrome

Question 41

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

Answer 41

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

Question 42

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

Answer 42

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

Question 43

diseases due to defect in DNA repair- Werner Syndrome Symptoms

Answer 43

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