Question

Give an account of polymerases found in eukaryotes.

Answer 1

RNA polymerase catalyses the synthesis of different types of RNA from the DNA.
(a) Prokaryotes contain only one type of RNA polymerase. Each molecule of this RNA polymerase has a core part containing 4 polypeptide chains (2a chains, one P chain & one pi chain) and a attached s(sigma) chain or a factor. The a factor is attached loosely to the core enzyme.

(b) In eukaryotes, the nucleus has three types of RNA polymerases (R. Roeder and W.Rutter, 1969) viz.-

1. Polymerase – I : It synthesizes three large rRNA (28S, 18S & 5.8S rRNA).
2. Polymerase – II : It synthesizes hn RNA (mRNA precursor).
3. Polymerase – III : It synthesizes small RNA (tRNA, 5S rRNA, S∩RNA).