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dna replication direction ???

can someone explain why replication occurs in the 5' to 3' direction but dna polymerase goes the opposite way please? i've been trying to figure this out for the better part of an hour lmao
Reply 1
Avatar for susiebe
susiebe
10
Hi

I think its because the active site of DNA polymerase is only complementary at the 3' end, so it can only add nucleotides at the 3' end.
Because the new strand and template strand are anti parallel DNA polymerase has to work in opposite directions.

I'm not sure if Ive exlained it that well as still learning myself so I will be interested in other peoples answers here
Reply 2
Avatar for TSRTD
TSRTD
11
Original post by susiebe
Hi

I think its because the active site of DNA polymerase is only complementary at the 3' end, so it can only add nucleotides at the 3' end.
Because the new strand and template strand are anti parallel DNA polymerase has to work in opposite directions.

I'm not sure if Ive exlained it that well as still learning myself so I will be interested in other peoples answers here

Yep this is correct. DNA helicase only unzips the DNA double helix from one direction. The antisense strand runs from 3' to 5' so DNA polymerase binds to the 3' end and can replicate this strand continuously. The sense strand runs from 5' to 3' and since DNA polymerase must bind to 3' it works in the opposite direction to the other strand. It will continuously work back along the strand, replicating the DNA to produce Okazaki fragments in discontinuous replication. As DNA helicase exposes more base pairs the DNA polymerase will repeatedly produce these DNA fragments by working back along the sense strand in the opposite direction to which it runs.
Original post by susiebe
Hi

I think its because the active site of DNA polymerase is only complementary at the 3' end, so it can only add nucleotides at the 3' end.
Because the new strand and template strand are anti parallel DNA polymerase has to work in opposite directions.

I'm not sure if Ive exlained it that well as still learning myself so I will be interested in other peoples answers here

ahh yes that makes sense. thank you!

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