DNA Replication

Question 1

DNA ligase

Answer 1

A linking enzyme essential for DNA replication; catalyses the covalent bonding of the 3’ end of one DNA fragment (such as an Okazaki fragment) to the 5’ end of another DNA fragment (such as a growing DNA chain)

Question 2

DNA polymerase

Answer 2

An enzyme that catalyses the elongation of new DNA (for example, at a replication fork) by the addition of nucleotides to the 3’ end of an existing chain.

Question 3

Helicase

Answer 3

An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands

Question 4

Primase

Answer 4

An enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template

Question 5

Okazaki fragment

Answer 5

A short segment of DNA synthesised away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of newly synthesised DNA.

Question 6

Semiconservative replication

Answer 6

Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and newly made strand

Question 7

Single-strand binding protein

Answer 7

A protein that binds to the unpaired DNA strands during DNA replication, stabilising them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA

Question 8

Topoisomerase

Answer 8

A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, topoisomerase helps to relieve strain in the double helix ahead of the replication fork.