dna replication

Question 1

describe the semi-conservative DNA replication model

Answer 1

• The double helix unwinds and the parental strands separate.
• Each parental strand acts as a template for the synthesis of daughter strand via complementary base pairing.
• Each daughter DNA molecule comprises one parental and one newly synthesised strand.

Question 2

list the steps in the semi-conservative DNA replication process

Answer 2

• Step 1 – Unwinding of DNA by helicase
• Step 2 – Binding of single-stranded DNA binding proteins
• Step 3 – Synthesis of RNA primer
• Step 4 – Elongation and synthesis of daughter strand
• Step 5 – Replacing RNA primer with DNA
• Step 6 – Closing nicks in DNA
• Step 7 – Re-winding of DNA helix

Question 3

where does the replication of DNA begin

Answer 3

at special sites called origin of replication

Question 4

function of helicase in DNA replication

Answer 4

recognises and binds to the origin of replication, causing the DNA molecule to unwind and unzip at the origin of replication. hydrogen bonds between the bases are broken and the DNA strands are separated

Question 5

what is the replication fork

Answer 5

a Y-shaped structure formed when the double helix is unwound, where exposed single-stranded DNA serves as a template

Question 6

how is a replication bubble formed

Answer 6

when two replication forks spread in both directions

Question 7

difference in number of origins of replication and replication bubbles between prokaryotic DNA and eukaryotic DNA, and why

Answer 7

as prokaryotic DNA is (usually) circular, prokaryotic DNA has a single origin of replication, and therefore only one replication bubble. eukaryotic DNA, on the other hand, being linear, has numerous origins of replication, and therefore many replication bubbles form.

Question 8

why do single-stranded DNA binding proteins bind to the separated strands of parental DNA?

Answer 8

to stabilise the single-stranded DNA and keep the strands apart, preventing them from