Epigenetics Flashcards
Heterochromatin
- dense
- inactive genes
Euchromatin
- open
- active genes
Nucleosomes
- 150 bases of (-) DNA wrapped around 8 (+) histone arms
- packed nucleosomes = chromatin
Chromatin Active
- open
- NOT methylated
- DNA sensitive to nucleases
lysine acetylation – remove (+) charge = lose wrap
KMT H3K4 – specific methyls to activate
HAT – acetyl added
Chromatin Repressed
- tight
- methylated
- DNA NOT sensitive to nucleases
KMT H3K9 = specific methyls to inactive
DNMT DNA = methylates
HDAC = remove acetyl
Methylation
DNA methyltransferase recognizes hemimethylated CpG sites
X-Chromosome Inactivation
wt - random inactivation
xic - strand can NOT be inactivated
one X chromosome remains active
Active X Chromosome = no XIST-RNA binds to XIC
Inactive X Chromosomes = XIST-RNA binds to XIC
Imprinting
Maternal Allele (no methyl)
- CTCF binds to insulator
- enhancer activates H9
Paternal Allele (methyl)
- methylate insulator + H9 – CTCF can’t bind
- enhancer activates Igf2
Normal Growth – m: Igf2 null p: Igf2+
Dwarf – m: Igf2+ p: Igf2 null
RNAe
active state –> transcript diced –> AGO binds –> repressed state
Paramutation
B’ suppresses B-I
B’ –> siRNA –> bind to AGO –> repression enzymes
- AGO complex binds in trans to silence B-I
Conjugation
- F factor transfer bacterial resistance to F- cell
OR - F factor transfer genetic info (homologous recombination with bacterial chromosome)
Transformation
- bacterial chromosome removed + fragmented
- fragments transformed to recipient cell
- homologous recombination with leu- == now grow
- close together genes – co-transform
Transduction
- phage inject DNA – cut up chromosome
- package bacterial DNA into phages + released
- phage inject into recipient cell
- homologous recombination with leu- == now grow
