unit 6 apbio

helicase

enzymes that unwinds DNA strand at replication fork

single strand binding protein

binds to and stabilizes single stranded DNA until it can be used as template

topoisomerase

relieves overwinding strain ahead of replication fork by breaking, swiveling, and rejoining DNA strands

primase

synthesizes an RNA primer at 5’ on leading strand and each 5’ end of every okazaki fragment on the lagging strand

DNA poly III

synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre existing DNA strand

DNA poly I

removes RNA nucleotides of primer from 5’ end and replaces them w DNA nucleotides

ligase

joins okazaki fragments of lagging strand. joins 3’ end of DNA that replaces primer on leading

nucleotide-pair substitution

replaces one nucleotide and its partner with another pair

silent mutations

doesn’t change the amino acid codon

missense mutation

codes for an amino acid, just not the correct one

nonsense mutation

codes for an earlly stop codon, almost always leading to a nonfunctional protein