DNA replication

Question 1

How the DNA Separates

Answer 1

• helicase separates (unzips) the two strands of DNA, resulting in a formation of a replication fork behing it
• the separated strands each provide a template for creating a new strand of DNA. The leading strand and the lagging strand

Question 2

Leading Strand Steps

Answer 2

• Primase starts the process making a small piece if RNA called a primer (this marks the starting point for the construction or the new strand of DNA)
• DNA polymerase binds to the primer and begins making the new strand of DNA
• DNA polymerase adds bases in one direction from the 5’ to 3’ end continuously
• The leading strand is made continuously by the DNA polymerase adding bases one by one in the 5’ to 3’ direction

Question 3

Lagging Strand Steps

Answer 3

• The lagging strand rubs in the opposite direction so DNA polymerase can only make this strand in a series of small chunks called Okazaki fragment
• Primase starts each fragment by attaching a primer to the lagging strand
• DNA polymerase then fills in the gap and adds a short row of bases in the 5’ to 3’ direction (Okazaki fragment)
• Primase adds another primer further down the lagging strand and DNA polymerase adds in another Okazaki fragment. This cycle continues until the lagging strand is replicated

Question 4

How the DNA is put back together

Answer 4

• Once both strands have been replicated exonuclease removes all the RNA primers from both strands of DNA and another DNA polymerase fills in the gaps left behind
• DNA ligase seals up the fragments of DNA to form a continuous double strand