What is the first enzymatic activity in DNA synthesis Endonu

What is the first enzymatic activity in DNA synthesis?

Endonuclease

Primase

Exonuclease

DNA polymerase

Ligase

Solution

Ans. Correct option. B. Primase.

The first enzymatic activity in DNA synthesis (among the available options) is Primase.

DNA primase (or, primase) binds to ssDNA strands during initiation period. It synthesizes small RNA primer to both the strands. DNA polymerase holoenzyme binds during elongation of DNA synthesis after primase has synthesized RNA primers. It extends the RNA primers with DNA nucleotide polymerization on it in 5’-3’ direction.

The exonuclease activity of DNA polymerase comes into action during repair or nick translation during elongation. Other than that, no other endonuclease or exonuclease participate DNA synthesis.

Ligase (DNA ligase) joins DNA fragments during nick translation much later than DNA pol begins to synthesize DNA.