Question

1. Which of the following is/are true about DNA replication?

   A) Primase is needed to initiate DNA replication on both the leading strand and the lagging strand.

   B) The sliding clamp is loaded once on each DNA strand, where it remains associated until replication is complete.

   C) Telomerase carries its own DNA molecule to use as a primer at the end of the lagging strand.

   D) Primase requires a proofreading function that ensures there are no errors in the RNA primers used for DNA replication

   		A
   		A and B
   		A, B and C
   		D

Answer 1

The correct statements about DNA replication are :-

(a) Only A

A) Primase is needed to initiate DNA replication on both the leading strand and the lagging strand.

?Primase is an enzyme that creates a primer on a DNA strand by adding RNA nucleotide complimentary to the DNA strand which occurs during the process of replication. After this elongation this piece is removed and refilled with DNA.

?The sliding clamp is loaded once in the leading strand but on the lagging strand it must be removed and reattached with every Okazaki fragments. It keeps DNA polymerase attached to the template while polymerase synthesize a new strand of DNA.

Since it is loaded more than once in the lagging strand so the above statement is incorrect.

? Telomerase carries its own RNA molecule to use as primer to extend the overhanging strand of telomere DNA by adding nucleotides to it. So the above statement is incorrect.

?The last statement is also incorrect about DNA replication. Primase don't require proof reading function, it is the DNA polymerase which does the proof reading during synthesis of DNA strands. The Primase enzyme creates a primer which is removed by exonucleases after elongation by DNA polymerase has occured.

So all statements are incorrect except A .

so the correct answer is statement A.