Ch 16 The Molecular Basis of Inheritance

Bacterial DNA replication proteins and their functions

Helicase

Unwinds parental double helix at replication forks

Single-strand binding protein

Binds and stabilizes single stranded DNA until it is used as a template

Topoisomerase

Relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands.

Primase

Synthesizes an RNA primer at 5’ end of leading strand and at 5’ end of each Okazaki fragment of lagging strand

DNA polymerase III

Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand

DNA polymerase I

Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides added to the 3’ end of adjacent fragment

DNA ligase

Joins Okazaki fragments of lagging strand; on leading strand, joins 3’ end of DNA that replaces primer to rest of leading strand DNA