DNA replication

Question 1

First stage of DNA replication (applies to both leading and lagging)

Answer 1

The DNA molecules unwind so that it can be split apart.

Question 2

Second stage (applies to both leading and lagging)

Answer 2

Weak hydrogen are broken using energy from ATP.

Question 3

Requirements

Answer 3

ATP ( to split apart the DNA strand), Enzymes (Ligase and DNA polymerase), Template strand, free nucleotides.

Question 4

Third stage (applies to both leading and lagging)

Answer 4

The template strands are now exposed forming a Y shaped replication fork.

Question 5

Fourth stage ( applies to only leading strand)

Answer 5

A primer attaches to exposed 3’ end of the template strand.

Question 6

Fifth stage (applies to leading strand only)

Answer 6

DNA polymerase adds free DNA nucleotides (which hydrogen bond to the complementary base of the template strand) to the 3’ end of the new DNA strand.

Question 7

Sixth stage (applies to leading strand only)

Answer 7

DNA polymerase also causes the formation of the strong chemical bonds attaching each newly added nucleotides to the growing strand.

Question 8

Eighth stage (applies to lagging strand)

Answer 8

DNA polymerase adds free DNA nucleotides to the 3’ end of the primes creating fragments

Question 9

Seventh stage (applies to lagging strand only)

Answer 9

Primers attaches to the exposed 3’ end of the template strand.

Question 10

Ninth stage ( applies to lagging only)

Answer 10

The enzyme ligase joins these fragments together to complete the lagging strand.

Question 11

Why leading is continuous and lagging is discontinuous

Answer 11

Since each new strand can only be synthesised in a 5’ to 3’ direction as the DNA polymerase can only add nucleotides to the 3’ end of the new strand. This means that the leading strand can always add nucleotides to the 3’ end as it is always being opened however the lagging strand must have a primer put in place every so often to add nucleotides to.