Histone acetyltransferase
enzyme that adds an acetyl group
removes + charge
activate gene expression
Histone deacetylase
enzyme that removes an acetyl group
phosphorylation
kinases add phosphates; and enzymes called phosphatases remove them
adds negative charge
activates gene expression
methylation
affect depends on protein
DNA Methylation
Methylation of CpG “islands” = gene silencing
DNA methylation: cancer
Tumor suppressor genes: roles in DNA repair, regulation of cell
division, metabolism.
• Block cellular proliferation and
cancer
• Hypermethylation of promoter prevents tumor suppressor
gene expression, cancer
more likely to develop. DNMT inhibitors
may be used to restore expression
DNA replication occurs in _____ phase
S
ORI
particular sequence in a genome at which replication is initiated
A + T are more likely to separate during DNA replication:
why?
they only have 2 H bonds whereas G-C have 3
less energy needed
difference between DNA primer and RNA primer
RNA primers are weaker and can synthesize without needing dNTPs
Topoisomerase
assists in undoing the supercoiling of DNA upstream from replication fork
start codon
ATG
stop codons
TGG TGA TAA
What do you need for PCR
DNA Polymerase (heat tolerant)
• Primers
• dNTPs
• A
DNA template (source for your sequence of interest)
• System for
changing the temperature
Taq polymerase
fixes mismatch bases
agarose gel can't properly size circular DNA. list the shapes from large to small
circle > wavy > helix > supercoil
proteins used in MMR
MutS (recognizes mismatch), MutL (mediator), MutH (introduces single nick), UvrD/Helicase (unwinds near nick), exonuclease (cuts until mismatch)
proteins used in BER
DNA glycosylases (recognize damaged bases), AP endonuclease (removes remaining backbone, phosphate, sugar),
proteins used in NER
spontaneous
UvrA/UvrB (identify the pyrimidine dimer), UvrC (cuts the strand
with
the dimer, about 12 bases removed), UvrD (separates
the
strands, damaged piece is removed),
proteins used in NHEJ
double strand DNA breaks eukaryotes
recognition of broken DNA ends by the
protein Ku
proteins used in HDR
MRN and CtIP nuclease (degrades), RPA (binds proteins), BRCA1 (end processing), BRCA2 (stabilize RAD51), RAD51 (displaces RPA),
BRCA1 and 2 and cancer
breast cancer genes
mutations can lead to cancer
Loss of BCRA2 will make it harder for strand invasion to
occur
during HDR