Question

What is DNA replication? What is the significance?

Answer 1

Hint: DNA is known to be a storehouse of genetic information. Replication is the process in which two complementary strands of DNA unwind and each strand serves as a template for synthesizing new complementary strands.

Complete step by step answer:
DNA replication is the process by which an organism duplicates its DNA into another copy that is passed on to daughter cells. It usually occurs before cell division and ensures that both the daughter cells get the exact same copy of the parent DNA. The specific regions in the genome of an organism where replication begins are called ‘origin’. The process involves the action of many different enzymes the first of which is helicase. It helps in the unwinding of the double-stranded DNA molecule. There exist certain proteins called Single-strand binding proteins (SSB) that stabilize the unwound DNA strands. Another enzyme named as Topoisomerase helps in reducing the stress that occurs in the molecule as a result of unwinding. This entire assembly, with unwound DNA which
looks like an inverted Y shape, is called the Replication fork.
Many theories for the replication model were introduced, out of which ‘semi-conservative’ is the widely accepted model. It was suggested by Meselson and Stahl. According to this process, parent DNA double helix results in two-hybrid DNA. Each of the daughter DNA molecules retains one strand from the parent and synthesizes a new one. The enzyme catalyzing the synthesis of DNA is DNA polymerase. Its fundamental reaction is phosphoryl group transfer between incoming nucleotides and the growing chain of DNA. Given below is a DNA replication process:
 

Note:
DNA polymerase can catalyze polymerization in 3’ to 5’ direction and hence continuous polymerization occurs on this strand i.e. it is the leading strand. Whereas, on the other strands, short segments of DNA are synthesized called Okazaki fragments which are joined later with the help of DNA ligases.