Question

1. a.) how long would it take in minutes to replicate the E. coli chromosome if it used unidirectional rather than bidirectional replication? Explain how you calculated this answer.

b.) not accounting for individual chromosomes and telomeres, i.e., use genome size, polyerization rate, and number of origins, how long should it take in hours to replicate the diploid human genome? Explain how you calculated this answer. why is this calculated time less than the observed time?

Answer 1

Ans. a) It will take around 40 minutes to replicate the E.coli if it used unidirectional mode of replication.

As we know the time required for the duplication of E.coli is 40 minutes. In the case of bidirectional replication the E.coli duplicates itself only in 20 minutes due to presence of large number of replisomes on ori site. But in the case of unidirectional repication, the replication will proceed in only one direction and the replication process will be slower than bidirectional method, so it will take whole of the 40 minutes to replicate.

b) It take only one hour to replicate the diploid human genome. There are around 150 million base pairs present in an human chromosome and the cell replicates at the rate of 50 base pairs per second. According to this rate it will take around a month to replicate the diploid human genome, but this do not happens due to the presence of multiple origin of replication (ori) sites. Due to multiple ori sites a number of replication process proceeds at a single chromosome.