AP Biology DNA replication enzymes flashcards

What is the role of helicase?

Helicase unwinds the DNA double helix at the replication fork by breaking hydrogen bonds.

Function of DNA polymerase?

DNA polymerase adds complementary nucleotides to the growing DNA strand during replication.

True or false: Ligase is involved in unwinding DNA.

False, because ligase joins Okazaki fragments on the lagging strand after DNA synthesis.

Difference between leading and lagging strand?

The leading strand is synthesized continuously; the lagging strand is synthesized in short fragments.

What initiates DNA replication?

RNA primer synthesized by primase provides a starting point for DNA polymerase.

Fill in the blank: DNA _______ synthesizes new DNA strands.

polymerase

What is the role of primase?

Primase synthesizes a short RNA primer to provide a free 3'-OH group for DNA polymerase.

True or false: DNA replication is semiconservative.

True, because each new DNA molecule consists of one original and one new strand.

What enzyme removes RNA primers?

DNA polymerase I removes RNA primers and replaces them with DNA nucleotides.

Which enzyme seals DNA fragments?

DNA ligase seals gaps between Okazaki fragments on the lagging strand.

Function of topoisomerase?

Topoisomerase relieves torsional strain ahead of the replication fork by making temporary cuts in the DNA.

What does exonuclease activity do?

Exonuclease activity allows DNA polymerase to remove incorrectly paired nucleotides during replication.

Difference between DNA polymerase I and III?

DNA polymerase III primarily synthesizes new DNA, while DNA polymerase I replaces RNA primers with DNA.

Fill in the blank: _______ stabilizes single-stranded DNA during replication.

Single-strand binding protein (SSB)

True or false: DNA ligase is required on the leading strand.

False, because the leading strand is synthesized continuously without gaps.

What keeps DNA strands apart during replication?

Single-strand binding proteins prevent re-annealing of the separated DNA strands.