Maintenance and use of genetic information Flashcards
What are the stages of the cell cycle
G1 = gap 1 S = DNA synthesis G2 = gap 2 M = mitosis
How does formation of replication forks occur?
Initiation proteins splits up double stranded DNA, then single stranded binding proteins prevent double hekix reforming
How is supercoiling prevented during genetic replication?
Unwinding of DNA in one region can lead to supercoiling in the rest of the DNA - may break it.
Topoisomerase enzymes break a phosphodiester bond to relax the chain
What direction does DNA polymerase run?
5’-3’
What are the two strands on either side of the transcription fork called?
Leading strand = continuously synthesised
Lagging strand = discontinuously synthesised, made up of Okazaki fragments which are later combined
What enzymes are involved in creation of the lagging strand?
RNA polymerase - initiates it DNA polymerase - extends it exonuclease - removes RNA primers DNA ligase - forms missing phosphodiester bond Primase makes RNA primers
What is the end replication paradox
End bit of DNA lost with each replication; eats into telomere
What are the types of point mutation?
Silent (no difference in amino acid)
Missense (one amino acid to another, Glu-Val in sickle cell)
Nonsense (one amino acid to STOP)
Indels
Small scale insertions or deletions
Cri du chat syndrome
Deletion of end of chromosome 5
Chronic myelogenous leukaemia
Translocation of pieces of chromosome 9 and 22
What does reverse slippage cause?
Gain of repeat of codon
What does forward slippage cause?
Loss of repeat of codon
How can UV light effect DNA?
Causes adjacent thymine AA’s to form dimers (covalently bond) preventing gene transcription
How does nucleotide excision repair work
Nuclease and helicase enzymes remove region with incorrect nucleotide; then region resynthesised.
