pls explain replication of dna and semiconservative nature of dna i detail?
The process through which DNA creates its own copies is known as DNA replication.
- At first, DNA double helix starts unwinding in several points. These points are known as origin of replication.
- Enzyme helicase helps in the process of unwinding by breaking the H- bonds of the paired nucleotides to break apart the two templates of DNA.
- By the action of enzyme primase, a small primer which is a small chain of RNA by polymerization is formed on the template at the point of origin of replication.
- After unwinding up to a certain point, DNA represents a Y – shaped replication fork.
- The enzyme DNA polymerase starts supplying nucleotides that are complementary to the nucleotides of the DNA template in 5’ – 3’ direction.
- The synthesis of new strand will be in opposite direction as both the strands run in antiparallel manner.
- The new strand that is formed on 3’ – 5’ strand of template DNA is a continuous strand in 5’ – 3’ direction and is known as leading strand. However the strand that is formed on the other template of double helix are formed in fragments and called lagging strand. The small fragments are called Okazaki fragment.
- The fragments are joined by the joining enzyme called ligase.
- During replication, DNA polymerase automatically goes back to the point of the strand where wrong base is formed and corrects it (proof reading) before proceeding to further replication.