DNA Replication

The leading strand is synthesised in one long piece, whereas the lagging strand in synthesised in a bunch of smaller pieces called Okazaki fragments.



DNA polymerase can only use nucleotides to synthesise DNA in a 5'-to-3' direction. Because the strands of the original DNA molecule point in opposite directions, on one strand, 5'-to-3' will point towards the replication fork, and on the other strand, 5'-to-3' will point away from the replication fork. Where it points towards the fork, DNA polymerase can just continually polymerise DNA in one long chunk, and this is the leading strand. Where it points away from the fork, it synthesises Okazaki fragments which begin at the fork and end at the previous Okazaki fragment.

Feel free to ask, if any of that was unclear or you have any further questions.

Hi, i had a question on dna and was wondering if you could please help (a level). is the active site of dna polymerase complementary to the 5' end, and if so of what? the template or new strand? also, is the new strand made in the 5' to 3' direction (and the enzyme moves down the template strand in the 3' to 5' direction)?

Hi, i had a question on dna and was wondering if you could please help (a level). is the active site of dna polymerase complementary to the 5' end, and if so of what? the template or new strand? also, is the new strand made in the 5' to 3' direction (and the enzyme moves down the template strand in the 3' to 5' direction)?

DNA Polymerase is complementary to the 3' end of new strand I think

What do you mean by that?

In the textbook it states that dna polymerase is complementary to the 3' of the newly formed strand. I do a-level btw, so my level of knowledge isn't as advanced

In the textbook it states that dna polymerase is complementary to the 3' of the newly formed strand. I do a-level btw, so my level of knowledge isn't as advanced

DNA Pol is an enzyme. It isn't 'complementary' to anything!

Could you say it's specific ? Or nah

Huh, I wouldn't have described it that way. I'd say it binds the 3' end of the newly formed strand and adds to it, but not that it's complementary to it. Usually I only use that word to describe nucleic acids (i.e. DNA and RNA) that bind each other in the very specific way that nucleic acids can.

Could you say it's specific?

DNA polymerase can only add nucleotides to a 3' DNA end, so it is specific in that sense, but how it becomes attached there is actually a bit more complicated. There are other enzymes involved in loading it onto DNA that needs to be replicated, and still more enzymes involved in creating an RNA primer that it can begin from (as occurs with every Okazaki fragment on the lagging strand). I recommend you just learn what your textbook says about it, lest I give you ideas that are beyond the scope of the A-Level course.

Oooh thank you for the clarification !