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