Question

“DNA replication is continuous and discontinuous on the two strands within the replication fork.” Explain with the help of a schematic representation.

Answer 1

Schematic representation of DNA replication: 

Explanation:

1. In order to create a replication fork, DNA replication begins at a location known as the origin of replication (ori).
2. The separated strands act as templates for the synthesis of new strands.
3. DNA replicates in the 5' → 3' direction.
4. Deoxyribonucleotide triphosphate, or dNTPs, serve as a substrate and source of energy for nucleotide polymerisation.
5. An enzyme called DNA polymerase creates a new DNA strand complementary to the template strand.
6. As the complete genome is duplicated, DNA polymerase keeps moving along the template strand and appending new nucleotides to the complementary or expanding strand.
7. The DNA polymerase synthesises one new strand (leading strand) continuously in the 5' → 3' direction.
8. The other new strand is synthesised in short segments (Okazaki fragments) in the 5' → 3' direction (discontinuous synthesis).
9. An enzyme called DNA ligase joins the Okazaki fragments to generate a new strand. This new strand is known as the lagging strand.