Question

Enzymes needed for formation of replication fork :

• A.
  RNA polymerase and DNA polymerase I
• B.
  Helicase and gyrase
• C.
  Hexokinase and aldolase
• D.
  Ligase and endo nuclease

Answer 1

The correct option is B

Helicase and gyrase
Helicase opens up the DNA at the replication fork. To avoid rewinding of the DNA. Single-strand binding proteins coat the DNA all over the replication fork. DNA gyrase (also referred to as topoisomerase) reduces supercoiling (relaxes tension) which builds up during DNA unwinding, preventing DNA breakage.

Topoisomerase operates in the region prior to the replication fork to prevent supercoiling.

Primase synthesizes RNA primers complementary to the DNA strand. In order to produce a bulk of the new DNA, DNA polymerase III expands its primers and adds them to the 3' end.

RNA primers are removed and replaced with DNA by DNA polymerase I. DNA ligase sealed the gaps between DNA fragments.

Therefore, to form replication fork, helicase and gyrase are essential.