Question

The diploid genome of Drosophila melanogaster is approximately 3.1x10^8 base pairs of DNA. DNA synthesis occurs at approximately 30 bp/second. In the early Drosophila embryo, the entire genome is replicated in 5 minutes. How many bidirectional origins of synthesis are required to replicate the genome this quickly?

Answer 1

166,666 is the answer.

Step-by-step explanation:

We can assume that the genome is one large linear molecule of DNA and that the origin of replication is at the midpoint of the given chromosome. We know that the replication fork moves in opposite directions, hence 60 bp will be replicated per second.

Assume that the origins are equally spaced and that initiation at all the origins will be simultaneous, the rate of replication of the drosophila melanogaster genome is:

3.1 x 10^8 bp/ (300s)= 10*10^6

It is given that in bidirectional replication, the replication fork proceeds at the rate of 60bps per second.

10*10^6 bp/60bp

= 166,666 bidirectional origins of synthesis are required to replicate the genome in 5 minutes.