Question

Mode of DNA replication in Escherichia is
A. Conservative and unidirectional
B. Semi conservative and unidirectional
C. Conservative and bidirectional
D. Semi conservative and bidirectional

Answer 1

Hint: E.Coli is a gram- negative bacteria and found in the intestine of warm blooded organisms. E. Coli are also found in some animals' gut and cause sickness.

Complete answer:
DNA replication is the duplication of DNA. DNA replication is semiconservative and bidirectional in nature as we know that the DNA contains two strands of daughter so from them one comes out from the parent which is known to be the template strand.
When the DNA replication starts the bonds between two hydrogen nucleotides get broken so the strands get broken by the enzyme activity and the action of helical enzyme so the DNA is Semi conservative in nature.

As we know that the two strands are in 5’-3’ and 3’-5’ direction. The DNA get synthesized by the help of DNA polymerase enzyme in the 5-3-2 direction on leading strand by the help of the polymerase enzyme and when the DNA polymerase enzyme started working in the opposite direction that is the lagging strand it starts synthesizing very short segments of DNA which are known as okazaki fragments in 3’-5’ direction.

So, the correct answer is D.

Note: E.Coli have the single origin of replication and it’s DNA also contains the Y shaped or fork shaped replication. As the replication is bidirectional in E coli, it involves the DNA replication into the two directions at a particularly same time period and results into a leading strand where the application is more likely to occur very rapidly and also a lagging strand which has a slower rate of replication. When both of these fragments are fused together by the help of DNA ligase it produces a free strand which is unfragmented.