Recap of replication and mitosis

Question 1

In prokaryotes, describe initiation

Answer 1

Initiation proteins bind to ori C, the origin of replication. This causes a short stretch of DNA to unwind. The unwinding allows helicase and other single stranded binding proteins to attach to the single stranded DNA, stabilising this confirmation.

Question 2

In prokaryotes, describe elongation

Answer 2

The 3’ OH group of the last nucleotide on the strand attaches to the 5’ phosphate group of the incoming dNTP. Two phosphates are cleaved off the dNTP, this hydrolysis supplies the energy required for the formation of the new phosphodiester bond that forms.

Question 3

In what direction does DNA replication occur?

Answer 3

5’ to 3’

Question 4

How does DNA replication overcome the fact that DNA pol can’t initiate a new nucleic acid chain?

Answer 4

Primase creates a short RNA chain primer which DNA pol extends from the 3’ end.

Question 5

How does DNA replication overcome the fact that the two template strands are antiparallel?

Answer 5

Creates a leading and lagging strand.
Primase creates one primer for the leading strand which continues in the 5’ - 3’ direction.
Primase creates a primer for each okazaki fragment in the lagging strands

Question 6

Describe prokaryotic termination

Answer 6

DNA pol I acts as an exonuclease and replaces RNA primers with DNA nucleotides. DNA ligase then selas the nick with a phosphodiester bond between the 5’ P group of the initial nucleotide added by DNA pol III and the 3’OH group of the final nucleotide added by DNA pol I

Question 7

What is the role of DNA pol III

Answer 7

Synthesis of DNA

Question 8

What is the role of DNA pol I

Answer 8

Exonuclease in 3’ - 5’ and 5’ to 3’ directions.

Question 9

Eukaryotes have a single origin of replication? true or false?

Answer 9

False - they have multiple ORCs

Question 10

What is the role of DNA pol epsilon

Answer 10

Synthesis of the leading strand

Question 11

What is the role of DNA pol delta

Answer 11

Synthesis of the lagging strand

Question 12

What is the role of DNA pol alpha

Answer 12

Synthesis of RNA primers

Question 13

What is the role of Cdt1/6

Answer 13

Replication licensing - this allows the ORC to initiate replication at the site it is found.

Question 14

What is the role of the MCM2-7 complex

Answer 14

Helicase activity

Question 15

What are the role of topoisomerases

Answer 15

Relewase of the torsion created behind the replication fork

Question 16

What is the role of RPA

Answer 16

Single strand stability

Question 17

What is the role of FEN1

Answer 17

RNA primer removal

Question 18

What happens during prophase

Answer 18

Chromosomes condense, each chromosome possesses two chromatids, the mitotic spindle forms.

Question 19

What happens during prometaphase

Answer 19

The nuclear membrane disintegrates, spindle microtubules attach to chromatids

Question 20

What happens during Metaphase

Answer 20

chromosomes line up on the metaphase plate

Question 21

What happens during Anaphase

Answer 21

Sister chromatids separate and move toward opposite poles

Question 22

What happens during Telophase

Answer 22

Chromosomes arrive at spindle poles, the nuclear membrane reforms and the chromosomes relax