Replication

Question 1

what is the enzyme that unwinds the DNA double helix in preparation for replication?

Answer 1

helicase

Question 2

describe process of replication

Answer 2

1. helicase enzyme unwinds the double helix and exposes the complementary strands (ssDNA proteins stop the strands from reannealing) - forms replication fork
2. Primase enzyme anneals Ran primers - puts a RNA primer down which starts replication
3. DNA pol binds to primer and reads 3’ to 5’ along each single strand, and adds complementary nucleotides 5’ to 3’
4. each nucleotide strand serves as a template for building a new complimentary strand = 2 identical copies of DNA.
5. after each fragment synthesised, DNA POL 1 swaps primer nucleotides for DNA nucleotides and ligase joins it all up.

Question 3

what enzyme adds nucleotides?

Answer 3

DNA polymerase

Question 4

what is the enzyme that joins the 2 strands together at en dot replication?

Answer 4

Ligase

Question 5

what type is DNA replication

Answer 5

semi conservative as each DNA molecule is made up of one old (conserved) strand and one new

Question 6

in which direction does RNA pol:
Read the strand
add nucleotides

Answer 6

Reads in 3' to 5' 
But adds (synthesises) in 5' to 3'

Question 7

what does anti parallel mean?

Answer 7

Each strand is anti parallel to one another so direction of replication is opposite for opposing sides

Question 8

what is the leading strand?

Answer 8

replication moves along replication fork, synthesising complementary strands and only requiring the initial primer.

Question 9

what Is the lagging strand?

Answer 9

polymerase goes one chunk at a time as the new template is made available. Chunks are called Okazaki fragments - each 1 requires its own primer for polymerase to bind and copy a new fragment

Question 10

what enzyme starts replication by laying down an RNA primer for DNA pol to bind?

Answer 10

Primase

Question 11

what ensures that the new DNA strands are identical after replication?

Answer 11

Complimentary base pair rules

Question 12

what does each DNA strand serve as?

Answer 12

a template for DNA replication

Question 13

what experiment demonstrates the semi conservative replication?

Answer 13

Meselson Stahl (E coli - nitrogen 15 heavy and nitrogen 14 light)

Question 14

Define a primer

Answer 14

A short nucleic acid sequence that provides a starting point for DNA synthesis