Match the columns.

Column-A (Enzyme/Protein)		Column-B (Role in DNA replication)
i.	Helicase	a.	Joins the 3' end of the new DNA fragment to the 5' end of the previous one
ii.	RNA primase	b.	Nucleotide polymerisation
iii.	DNA polymerase	c.	RNA primer synthesis
iv.	DNA ligase	d.	Opens up the DNA double helix

The correct answer is i - d, ii - c, iii - b, iv - a.

Key Points

•  The correct answer is option 3, i - d, ii - c, iii - b, iv - a.
• DNA ligase joins the 3' end of the new DNA fragment to the 5' end of the previous one, thus it plays a role in the joining of Okazaki fragments.
•  RNA primase synthesizes a short RNA primer that provides a 3'-OH group for DNA polymerase to extend the new strand.
• DNA polymerase is responsible for nucleotide polymerization, which means it adds nucleotides to the 3'-OH end of the growing strand during DNA replication.
•  Helicase is an enzyme that unwinds the double-stranded DNA during DNA replication, thus it plays a role in the initiation of replication.

Additional Information

•  Helicase is an enzyme that unwinds the double-stranded DNA during DNA replication, thus it plays a role in the initiation of replication. It separates the two strands of DNA by breaking the hydrogen bonds between the complementary base pairs. This opens up the DNA double helix and allows DNA replication to proceed.
• RNA primase synthesizes a short RNA primer that provides a 3'-OH group for DNA polymerase to extend the new strand. The RNA primer is later removed by an exonuclease and replaced with DNA nucleotides by DNA polymerase.
• DNA polymerase is responsible for nucleotide polymerization, which means it adds nucleotides to the 3'-OH end of the growing strand during DNA replication. It also has proofreading activity, which helps to correct errors that may occur during replication.
•  DNA ligase joins the 3' end of the new DNA fragment to the 5' end of the previous one, thus it plays a role in the joining of Okazaki fragments. Okazaki fragments are short, discontinuous pieces of DNA that are synthesized on the lagging strand during DNA replication. DNA ligase seals the gaps between the fragments to form a continuous strand.