Chapter 16 - The Molecular Basis of Inheritance Flashcards
DNA replication: synthesis of leading strand (3 steps)
- helicase unwinds paternal double helix, binding protein stabilizes strands
- RNA primer is made and leading strand is synthesized by DNA pol III
5’ to 3 - strand is elongated as fork continues
DNA replication: synthesis of lagging strand (6 steps)
- primase join RNA nucleotides to primer
- DNA pol III adds nucleotides to primer forming okazaki fragment 1
- DNA pol III detaches at next RNA primer
- fragment 2 is primed, process repeated
- DNA pol I replaces RNA with DNA adding nucleotides to 3’ end of fragment 1 and 2
- DNA ligase forms a bond between new DNA and fragment 1
helicase
unwinds parental double helix at replication forks
single-strand binding protein
binds to and stabilizes single stranded DNA until it is used as a template
topoisomerase
relieves unwinding strain ahead of replication forks by breaking, swivelling, 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 pol III
synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand
DNA pol I
removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides
DNA ligase
- joins okazaki fragments of lagging strand
- joins 3’ end of DNA that replaces primer to the rest of the leading strand
nucleotide excision repair (DNA damage)
3 steps
enzymes detect and repair damaged DNA
- nuclease cuts out and removes damaged DNA
- repair synthesis by DNA polymerase fills in missing nucleotides
- DNA ligase seals free end of new DNA to old DNA
telomeres
postpone erosion of genes near ends of chromosomes
-shortening is connected to aging/limiting cancer growth; cell divisions)
enzyme telomerase
catalyzes lengthening of telomeres in germ cells (cancer cells persist)
DNA pol 1 (polymerase table)
template: DNA
product: DNA
primer: yes
direction: 5’-3’
substrate: dNTPs
proofread?: yes
frequency: 1x
primase (polymerase table)
template: DNA
product: RNA
primer: no
direction: 5’-3’
substrate: NTPs
proofread?: no
frequency: 1x
telomerase (polymerase table)
template: RNA
product: DNA
primer: no
direction: 5’-3’
substrate: dNTPs
proofread?: no
frequency: 1x