DNA Replication Flashcards
(41 cards)
origins of mutations: human males vs females
human males: much more divisions in germ cells
human females: fewer divisions in germ cells
frequency of mutations: (male sperm 10-50X female egg)
DNA replication
- enzymatic/structural/regulatory
enzymatic: nucleic acids as substrates
- DNA: restriction enzymes, topoisomerases, telomerases, methylases, polymerases, etc
- RNA: tRNA synthetases, polymerases, polyadenylases
structural: change in DNA/RNA structure
- helicases, histones, TBP (tata-binding proteins)
regulatory: binding to nucleic acids
- in both transcription (DNA binding) and translation (RNA binding)
Type of protein-nucleic acid interactions (4)
- ionic
- H bonds
- van der waals
- hydrophobic interactions
*also stabilize tertiary and quaternary protein structures
replication is _____ (style of conservation)
semiconservative
replication origin (prok vs euk)
prok: bacterial genomes and plasmids often have only 1
euk: multiple origins
replicon meaning
entire region of DNA replicated from one origin
(a piece of DNA which replicates as a single unit)
experiment that confirmed bidirectionality in DNA replication
pulse-chase experiment
- pulse of ^3H-T (tritium isotope), followed by “chase” of unlabeled T
- light up areas showed bidirectional growth (going in two directions)
discovery of enzymes in DNA rep
- studied prok w genetic and biochemical approaches
- make a mutant pop, screen for DNA rep mutants
- purify enzymes needed for rep
- assay: add labelled dNTP to necessary DNA rep enzymes, template DNA, and measure how much label is in new DNA
what does DnaA do in DNA rep?
initiation
what do single-strand binding proteins do in DNA rep?
they sheathe strands (so don’t reanneal)
what is helicase AKA?
DnaB
what is primase AKA?
DnaG, RNA polymerase
what are clamp loader and sliding clamp AKA?
clamp loader - DnaC
sliding clamp - beta clamp
replisome meaning
all the proteins that function at the replication fork, as part of DNA synthesis
3 problems in copying DNA by DNA pol:
- DNA pol can’t break inter-chain H-bonds at point of origin (need other molecules)
- DNA pol can’t start chains, only elongate (needs primer @3’OH)
- DNA pol can only add from 3’OH end (chain always grows in 5’-3’ direction)
3 ways to generate 3’ ends (for DNA rep), used by diff organisms
specific RNA pol
- synthesize small segment of RNA
- in DNA rep for prok and euk
nicked DNA
- happens in rolling circle replication; some phages do this
primed nucleotide
- some viruses can do this; also at end of euk rep (telomerase)
leading strand vs lagging strand
leading strand - continuously made from a single primer, 5’-3’
lagging strand - DIScontinuous, from multiple primers, also 5’-3’
what are okazaki fragments, what are they joined by?
lagging strand segments
joined by DNA pol I and ligase
how many replication forks in replication bubble?
2 replication forks in 1 replication bubble
processivity meaning
how fast and continuous the polymerase copies (high processive pol are more efficient)
initiation of replication in E. coli (origin of rep name, bp#, characteristic)
OriC, ~245bp
A-T rich 13 bp (3)
repetitive 9 bp (DnaA boxes, 4)
initiation depends on ______ of oriC
methylation
initiation depends on methylation of oriC:
- N6 of adenine is methylated in sequence GATC (copies exist in oriC)
- note: methylations can happen on C and A residues in DNA (prok)
methylation is epigenetic/trans-generational?
epigenetic
- template keeps methyl but new strands don’t, so not passed to future strands (hemi-methylated DNA)
