DNA replication, the cell cycle and mitosis Flashcards Preview

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Flashcards in DNA replication, the cell cycle and mitosis Deck (19):
1

Explain semi-conservative DNA replcation

Each strand forms a template for a new strand of DNA

2

What enzyme unwounds the DNA helix before replication can occur?

This is done by a DNA helicase, an enzyme that uses ATP as source of energy to break hydrogen bonds between base pairs.

3

What does DNA polymerase do?

DNA polymerases add nucleotides to the 3’ end of a growing chain.

4

What does DNA polymerase require?

a template strand an oligonucleotide primer a supply of deoxynucleotide triphosphates (dNTPs) add pic

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5

In what direction does DNA replication occur?

5' to 3' direction add pic

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6

What drives the reaction for DNA replication?

DNA synthesis is driven by the release of energy from the hydrolysis of the triphosphates. add pic

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7

What is required on the deoxyribose for DNA replication to occur?

A free 3’ hydoxyl group is required. add pic

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8

What is the name of the discrete points on the DNA molecule wher replication begins?

Origins of Replication

9

What is the site of DNA synthesis called?

Replication fork add pic

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10

What enzyme synthesizes the primer?

RNA polymerase called DNA primase

11

List the steps for DNA synthesis on the Lagging strand

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12

Why is DNA synthesis discontinous on the lagging strand?

it requires a series of DNA primers add pic

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13

Explain the steps which joins the okazaki fragments?

A special ribonuclease removes the RNA primer using a 5' to 3' exonuclease activity. DNA polymerase then synthesises DNA through the RNA primer region DNA ligase joins the two adjacent strands of DNA together using ATP. add pic

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14

What removes the RNA primer?

A special ribonuclease removes RNA primer using a 5’ to 3’ exonuclease activity

15

Describe the proof-reading mechanism of DNA?

Before a new nucleotide is added, the previous nucleotide is checked for correct base-pairing. Any incorrect bases are removed by 3’ to 5’ exonuclease activity of DNA polymerase. A new, correct nucleotide is then added. add pic

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16

Describe the replication of a E.coli chromosome by drawing a diagram?

In E.coli, replication starts at a unique origin, OriC. Two replication forks proceed simultaneously in opposite directions. The two forks meet at the other side of the circular chromosome. add pic

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17

Eukaryotic chromosomes are linear and very long. How does the cell manage to replicate the whole DNA molecule?

Each replication origin gives bi-directional replication forks. Replication is finished when all the forks have met. add pic

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18

Define the different stages of the cell cycle?

G0: cells which have stopped dividing

G1: DNA of each chromosome present as a single linear double helix of DNA

S phase: the DNA is replicated

G2: each chromosome has two identical sister chromatids

Mitosis: the two chromatids separate to the daughter cells

 

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19

Explain how chromosomes segregate at metaphase by drawing a diagram?

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