NEET BIOLOGY

Detailed explanation-1: -Since DNA polymerase requires a free 3’ OH group for initiation of synthesis, it can synthesize in only one direction by extending the 3’ end of the preexisting nucleotide chain. Hence, DNA polymerase moves along the template strand in a 3’–5’ direction, and the daughter strand is formed in a 5’–3’ direction.

Detailed explanation-2: -coli polymerase I has 3′ to 5′ as well as 5′ to 3′ exonuclease activity. The 5′ to 3′ exonuclease operates in the direction of DNA synthesis and helps remove RNA primers from Okazaki fragments.

Detailed explanation-3: -DNA polymerase is able to add nucleotides only in the 5’ to 3’ direction (a new DNA strand can be only extended in this direction). It also requires a free 3’-OH group to which it can add nucleotides by forming a phosphodiester bond between the 3’-OH end and the 5’ phosphate of the next nucleotide.

Detailed explanation-4: -coli, the DNA polymerase that handles most of the synthesis is DNA polymerase III. There are two molecules of DNA polymerase III at a replication fork, each of them hard at work on one of the two new DNA strands. DNA polymerases can only make DNA in the 5’ to 3’ direction, and this poses a problem during replication.