Question

5. a) Draw a diagram of a replication bubble that shows two replication forks (mark them clearly) and indicate all of the following for one of the replication forks: newly synthesized leading and lagging strands (label 5' and 3 ends), RNA primers, DNA polymerase, helicase, and gyrase (topoisomerase). b) There are three enzymes in the list in part a. What function(s) do each of these play in DNA replication? You can answer this here, or include it on your diagram. Hint. One of these enzymes has multiple functions, you must mention at least two for full points.

Answer 1

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This is the replication fork. You can change the colour scheme according to your need.

As for the second part of the question :-

Activity of different enzymes :-

1) Helicase : Helicase is an enzyme and during replication it separates the two strands of DNA.

2) RNA primers: DNA Polymerase can not just use a template parental strand and synthesize the DNA. It needs a starting point and that is provided by RNA primers. So, RNA primers provide DNA Polymerase III a strand to work upon and use as a starting point.

3) Gyrase: Gyrase is the enzyme responsible for unwounding of DNA. Basically, DNA is negatively supercoiled, like a spring. Gyrase removes this tension, unwind the DNA. Gyrase role is thus, unwinding of DNA and control the topological transition of DNA

DNA Polymerase: As the name suggest, it polymerize the DNA Out is the enzyme responsible for the synthesis of new DNA strands from parental DNA strand.

It also have another activity, that is if proofreading and editing (editing is called exonuclease activity too). What does this is that as DNA Polymerase III is synthesizing DNA, it also proofread, i.e, it keep on checking if the nucleotide incorporated into the new DNA strand is right or not. Adenine should be paired with Thymine and vice versa while Cytosine should be paired with Guanine and vice versa.

If by mistake DNA Polymerase have added wrong nucleotide, it checks it and remove it by using its Exonuclease activity.

Exonuclease activity is 3' - - > 5'

Thank you..