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Genetics 11/19

Terms in this set (38)

what are the 2 main methods that eukaryotic cells use to regulate transcription initiation
1 binding transcription factors to enhancers
2 DNA methylation in promoter regions (a biochemical modification of DNA itself)
binding transcription factors to enhancers
modulates the spatial and temporal expression of many genes that are expressed only in particular tissues at specific times during development
DNA methylation in promoter regions (a biochemical modification of DNA itself)
a methyl group is added to the 5th carbon of the cytosine base in a 5' CpG 3' dinucleotide pair on one strand of the double helix
DNA methylation
a methyl group is added to the cytosine base in a 5' CpG 3' dinucleotide by DNA methyl transferases (DNMTs)
[clicker quiz] methylation happens at
the C of CG sequences running 5'->3'
CpG islands
are commonly 1000-2000 bp in length and contain a high number of CpG sites
in vertebrates and plants, CpG islands
occur near many promoters of genes
DNA methylation usually
inhibits the transcription of eukaryotic genes
70% of C residues in CpG regions in humans
are methylated, implying that it is significant for transcription
DNA methylation ultimately controls
gene transcription
methylation is important for controlling
expression of housekeeping genes that control homeostasis
-also some specific cell type gene expression
methylation can alter gene expression heritability
without changing the base sequences of DNA
called epigenetic phenomenon
C. elegans and yeast have
no DNA methylation
other inverts and lower euks have
very little methylation
drosophila has
disagreement in whether or not 5-methylcytosine is present
because chromatin structure effects initiation, and methylation effects chromatin structure,
methylation effects initiation
chromatin remodeling can expose
the promoter and give rise to transcription
-
unmethylated CpG islands
can be transcriptionally active, so transcription factors can bind to these to prevent methylation and initiate transcription
DNA methylation can
silence trancription, closes chromatin structure
DNA methylation patterns are copied
during DNA replication
-can recognize methylated DNA and then methylates the newly synthesized strands
methylation is usually long term,
it is maintained through cell division
silencing
long term repression through DNA methylation
gene silencing is an epigenetic change
bc there are no recessive mutations in the gene sequence associated with it
[clicker quiz] human promoter region is found to be highly methylated. hypothesis is that downstream transcription is:
downregulated by this methylation
[clicker quiz] Yeast promoter region is found to be highly methylated. hypothesis is that downstream transcription is:
no impact
CpG regions are under
selection in vertebrates
human genome is ______ GC and ________ AT
42%, 58%
there is a lower frequency than expected of C followed by G, which means
that natural selection os eliminating CG sequences
k-mer
a sequence of length k
k=2, a dimer
k=3, a trimer
genomes show non-random
k-mers
mendelian rule that parental origin of allele
does not affect F1 phenotype
-not always true
genomic imprinting
expression of a gene depends on whether it was inherited from the mother or father
-occurs with some genes in mammals (100 or so genes)
-primarily epigenetic
paternally imprimted gene is
transcriptionally silenced if it was transmitted from the father
-maternally inherited gene is expressed
maternally imprinted gene is
transcriptionally silenced; father's gene is expressed
in somatic cells, genomic imprint is
maintained during mitosis, remaining throughout the life of the mammal
in germ cells, genomic imprints are
Reset during Meiosis before being passed on to the next generation
DNA mehylation is removed during
early meiosis, and new sex-specific DNA methylation is generated before final gamete formation
Prader-Willi syndrome and Angelman syndrome are both associated with
small deletions in chromosome 15
deletion inherited from Father = P-W
from mother = AS
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