Question

The Okazaki fragments are linked by the enzyme
A) Helicase
B) Topoisomerase
C) Ligase
D) DNA polymerase

Answer 1

Hint:Okazaki fragments are short newly synthesized DNA sequences.These fragments are important for the synthesis of DNA.

Complete Answer:
Okazaki fragments are short pieces of DNA synthesized repeatedly on the lagging strand template. Their sizes range between 1000 to 2000 nucleotides in bacterial cells and 100 to 200 nucleotides in eukaryotic cells. They were discovered in the 1960s by the Japanese molecular biologist Reiji and Tsuneko Okazaki and their colleagues.
During DNA replication, the double helix is unwound and the complementary strands separate with the help of the enzyme DNA helicase creating a replication fork. After this, DNA primase and DNA polymerase begin to create a new complementary strand in the 5’ to 3’ direction. Both the template strands are replicated in different ways. The synthesis of the leading strand occurs in the 5’ – 3’ direction and forms a continuous strand. The directionality of the lagging strand is also the same but because its template is in 5’ – 3’’ direction, the polymerases have to work backwards from the replication fork. It causes periodic breaks in the lagging strands. These short pieces are called Okazaki fragments.
Enzymes involved in the formation of Okazaki fragments are:
Primase- Adds RNA primers to the lagging strand which allows the synthesis of these fragments from 5’ to 3’.
DNA polymerase δ- New DNA is made to synthesize DNA in the 5’ to 3’ direction. Extension of the newly synthesized fragment is done and the removal of RNA and DNA segment.
Flap endonuclease 1 (FEN1) - this enzyme processes the Okazaki fragment and removes the RNA primer along with DNA polymerase I.Enzyme ligase connects (ligates) the two Okazaki fragments into one continuous newly synthesized complementary strand.
DNA ligase I- DNA ligase I connects the Okazaki fragments during the synthesis.

Hence, the correct option is option C, ‘Ligase’.

Note:The ligase joins the Okazaki fragments to form a newly synthesized, continuous, complementary strand.DNA ligase are linked by catalyzing the formation of a phosphodiester bond.