Lecture 16

Question 1

Characteristics of Prokaryotic Replication
To have…. chromosomes
Is also…. (direction)

Answer 1

Are said to have singular circular chromosomes.

Replication is also bi-directional from the single origin of replication.

Question 2

Function of RNA Polymerase

Answer 2

An enzyme that makes small RNA primers (starting point for DNA polymerisation)

Question 3

Function of Helicase?

Answer 3

Unzips the DNA by breaking the H-bonds.

Question 4

Function of Topoisomerase?

Answer 4

Releases tension generated by unwinding the DNA helix. It is later then joined back together.

Question 5

Function of RNA Primase?

Answer 5

Makes an RNA primer starting point for DNA replication. It helps to leave a 3’ OH group.

Question 6

Function of Single Strand Binding Proteins?

Answer 6

1. Keeps separated strands seperate

2. Prevents degradation of ssDNA by enzymes and proteins.

Question 7

Function of DNA Polymerase III

Answer 7

Adds new nucleotides (dNTP) complementary to parental strand of DNA. Only will make DNA in the 5’ - 3’ direction.

Question 8

Function of DNA Polymerase I

Which strand and when does DNA Poly I attach?

Answer 8

1. Remove the RNA primer
2. Replace the gap with DNA nucleotides

Happens on the lagging strand and will attach after the Okazaki Fragments have been formed.

Question 9

Function of DNA ligase?

Answer 9

Formation of a phosphodiester bond between the Okazaki fragments together.

Question 10

Characteristics of Eukaryotic Replication

Contains … chromosomes
Have multiple…

Answer 10

Contains MULTIPLE, LARGE LINEAR chromosomes

Can have multiple SITES OF ORIGIN OF REPLICATIONs.

Question 11

Characteristics of Eukaryotic Replication

Contains … chromosomes
Have multiple…

Answer 11

Contains MULTIPLE, LARGE LINEAR chromosomes

Can have multiple SITES OF ORIGIN OF REPLICATIONs.

Question 12

What enzyme is involved in fixing errors DURING replication? What are the key steps that it does to fix the DNA?

Answer 12

EXOnuclease.

It directly removes the incorrect base form the ends of strands.

Question 13

What enzyme is involved in fixing errors AFTER replication? What are the key steps that it does to fix the DNA?

Answer 13

ENDOnuclease

Masses of DNA are removed either side of the error, then Polymerase attaches new nucleotides and Ligase joints the ends.

Question 14

What is the purpose of PCR?

Answer 14

To target a specific DNA region, and through cycles of heating and cooling, replicate the specific DNA.

Question 15

What is the purpose of PCR?

Answer 15

To target a specific DNA region, and through cycles of heating and cooling, replicate the specific DNA.

Question 16

What happens at the DENATURING stage? What temperature does it take place?

Answer 16

This helps to break the H-bonds between bases to ssDNA.

94-98°C

Question 17

What happens at the ANNEALING stage? What temperature does it take place?

Answer 17

Primers will anneal (attach) to the DNA template strand.

45-70°C

Question 18

What happens at the EXTENSION stage? What temperature does it take place?

Answer 18

Buffers, Divalent Cations will aid the Polymerase to add nucleotides.
72°C

Question 19

What happens at the REPEAT stage? On average how many times?

Answer 19

Repeat steps 2-4 around 25-35 times for the exponential increase in DNA.