Question

What is replication and where does it occur?

Answer 1

DNA replication:

1. DNA replication is the process by which DNA makes a copy for itself(DNA duplication).
2. It occurs in the nucleus of the cell during the S-phase of the cell cycle.
3. Thus, any discrepancy during the S-phase may result in polyploidy.
4. DNA replication is semiconservative in nature.

DNA replication occurs in two stages:

1. Unwinding of strands: The separation of two strands of DNA after the breakdown of H-bonds is known as unzipping or unwinding. It is carried out by the enzyme ‘helicase’ in eukaryotes. This initiates via formation of replication fork that has origin of replication.
2. Formation of new strand: Out of two strands, replication on one strand (3'⇢5') is continuous-leading strand, while on the other strand (5'⇢3'), it is discontinuous- lagging strand. The fragments of new DNA formed on lagging strand are termed ‘Okazaki fragments’. The formation of a new strand is catalyzed by DNA-dependent DNA polymerase.