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Cell biology 1220 > DNA replication > Flashcards

DNA replication Flashcards

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1
Q

What is the difference between meiosis and mitosis?

A

Mitosis - 2 daughter cells produced

Meiosis - 4 gametes produced

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2
Q

What are the divisions of interpahse in the cell cycle?

A

G1 - preperation for replication
S - DNA replication
G2 - Cell grows in size

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3
Q

During which stage does DNA replication occur?

A

Interphase - S phase

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4
Q

What are the 3 theories for DNA replication

A

Conservative replication
Semi-conservative replication
Dispersive replication

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5
Q

Describe the conservative model for DNA replication

A

Entirely new double strand of DNA is made

Over time the N15 strand becomes a decreasing fraction of the population

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6
Q

Describe the semi-conservative model for DNA replication

A

1 strand is synthesised and 1 strand is passed on - original parental strands are split over 2 daughter strands

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7
Q

Describe the dispursive model for DNA replication

A

Parental DNA is divided between each new daughter strand during every replication

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8
Q

What enzymes are needed for semi-conservative replication?

A

Topoisomerase - unwinds double helix and cuts the chain
Helicase - unwinds double helix
DNA pol III - travels from 5’ to 3’ joining nucleotides
DNA ligase - links toghether okozaki fragments are repairs cuts made by topoisomerase
Primase - a type of RNA polymerase that synthesises a 60 nucleotide long primer which begins DNA replication
DNA pol I - repairs DNA and removes primer
DNA pol II - repairs DNA

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9
Q

What direction does DNA Pol III travel in?

A

DNA pol III travels from 5’ to 3’. It synthesises base addition from the 3’ end of the primer. Because the strand are anti parallel, DNA pol will be travelling in opposite directions

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10
Q

What proteins are needed in semi-conservative replication?

A

Single strand binding proteins (SSB’s) - bind to single strands to prevent them re-annealing or binding to themselves
Sliding clamp - protein which holds DNA pol II on the strand

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11
Q

What substrates are needed in semi-conservative replication?

A

Deoxynucleotide triphosphates - dATP, dGTP, dCTP, dTTP

Ribonucelotide triphosphates - ATP, UTP, CTP, GTP

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12
Q

What is meant by replicon?

A

Single piece of DNA that replicates

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13
Q

What is meant by the origin?

A

Initiaition site where replication starts

Initiation proteins target the A-T rich origin - only 2H bonds need breaking

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14
Q

What is meant by the pre-replication complex?

A

Pre replication complex - unzips the double helix, creating the replication bubble

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15
Q

What is meant by replication bubble?

A

Replication bubble - structure formed when double strand is unzipped

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16
Q

What is meant by replication fork?

A

Replication fork - point where double strand separates

17
Q

Describe the prokaryotic replicon

A

Prokaryotic chromosomes are circular - consist of a single replicon.
The terminus site is 180 degrees opposite the origin

18
Q

Describe the eukaryotic replicon

A

Eukaryotic chromosomes are linear - have multiple replicons and origins

19
Q

Step 1 of DNA replication

A
  1. Topoisomerase cuts strand at origin
  2. DNA helicase unwinds DNA to 2 single strands, creating a replication fork
  3. SSB’s coat strands to prevent re-annealing
20
Q

Step 2 of DNA replication

A
  1. RNA primase synthesises a 60 nucleotide primer complementry to open chains
  2. Ribonucleotides in the primer bind to the each strand
21
Q

Step 3 of DNA replication

A
  1. DNA Pol III and clamping proteins bind to the 3’ end of the primer
  2. DNA Pol III attaches deoxyribonucleotides to the 3’ end of the primer
  3. The clamping protein is released allowing DNA polymerase to slide to the 3’ end of another primer
22
Q

Where does DNA Pol III attatch during DNA replication?

A

DNA Pol III attatches to the 3’ end of the primer

23
Q

Can DNA polymerase initiate replication?

A

DNA Pol cannot innitate replication, it can only extend the strand. RNA PRIMASE INNITIATES REPLICATION

24
Q

What does the release of the clamping proteins allow DNA polymerase to do?

A

The release of the clamping protein allows DNA Pol III to slide to the 3’ end of the next primer

25
Q

Describe replication on the lagging strand

A

RNA polymerase can only synthesize short chains (Okazaki fragments) before coming to an RNA primer

26
Q

What is needed to remove RNA primers from newly synthesised strands? What happens to the RNA primers?

A

DNA Pol I, helicase and endonuclease is used to hydrolyse phosphodiester and H bonds in the primer.
The ribonucleotides removed from RNA primers are then used to synthesise more primers

27
Q

What is used to join okazaki fragements? What is needed?

A

DNA ligase joins okozaki fragments at the 5’ end.

ATP or NADP is needed.

28
Q

Why is DNA replication unable to reach the very ends of the chromosone?

A

The telomere prevents this

Cell biology 1220 (11 decks)

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