Question

If we mutate the DNA ligase and observe the length of the replicated strands in different time slots after replication initiation, what will we observe?

(a) The DNA will gradually increase in length till it is fully replicated

(b) Small fragments of DNA will be obtained increasing in number with time

(c) Mixture of small and long Fragments of definite length from the start whose concentration simply increases with time

(d) At first small fragment, then two separate bands showing long fragment with increasing length and short fragments of definite length.

I have been asked this question in class test.

My question is based upon DNA Replication Prokaryotes topic in portion DNA Replication of Cytogenetics

Answer 1

Right choice is (d) At first small fragment, then two separate bands showing long fragment with increasing length and short fragments of definite length.

Best explanation: The small fragments are the Okazaki fragments of lagging strand while the longer is the leading stand DNA. While leading strand grows in length the Okazaki fragments in absence of ligation to each other results in small fragments of definite length.