Unit 3 Exam lecture 20 Flashcards
Phenotypes and processes transmitted to cells but not the result of genome sequence are called
epigenetic changes
Are epigenetics heritable
yes
Explain the process how newly synthesized DNA strands get methylated
After replication, half of double strand is methylated and half is unmethylated, methyl transferases add methyl groups to unmethylated strands
What is Dnmt3
active gene in female honey bees that stimulates methylation of genes for queen characteristics
What silences Dnmt3
royal jelly (siRNAs)
What happens early in development if a worker bee female is injected with siRNA that targets Dnmt3
those bees will become queens
royal jelly is an example of
an siRNA
What are the three ways that histones can be modified
methylation, acetylation and phosphorylation
Modification of histones are carried out by which proteins
polycomb protiens (PcG proteins)
PCR2 is what and does what
it is a PcG protein that adds two methyl groups to lysine 27 of H3
What happens when PcGs are mutated
they become non functional causing major developmental changes in phenotype
What do PcGs do
proteins which are responsible for the modification of histones
What is genomic imprinting
when one copy of a gene or group of genes is switched off
How can genetic diseases arise around genomic imprinting
One copy of a gene is silenced and the other active, if the active copy gets deleted then it can cause a genetic disease
Prada-Willi and Angelman syndroms are exampls of what
Genetic diseases due to deletion of non genomic imprinted copy of gene
the r1 locus in corn controls what
kernel color
Rr allele is for
purple kernels
the Rst allele is for
spotted kernels
RrRst codes for what colored kernels
spotted kernels
Subsequent Rr plants after being RrRst will produce which kernels and why
spotted kernels due to interaction of alleles that lead to heritable change in the Rr allele
What are the three characteristics of paramutation
- newly stablished expression pattern is transmitted to future generation even though the original allele is absent
- altered allele is now able to convert other alleles to new phenotype
- no associated DNA sequence different in altered alleles
Interaction of alleles at b1 locus code for
pigmentation for amount of anthocyanin
Epialleles are what
a specific DNA methylation pattern at a given locus
B-I B-I gives what color plant
purple
B’ B’ plants give what color plant
green
Crossing a B-I B-I and a B’ B’ gives what genotype plant
B-I B’ but then a paramutation occurs where the B’ changes the B-I into a B’*
What can B’* do once it has been paramutated
it can now convert B-I alleles
What are the differences between the B-I and B’ genes
both have tandem repeats upstream of the protein coding sequence however B’ genes express the epiallele of a highly methylated tandem repeat region
Tandem repeats of the B locus in corn act like what
enhancer sequences, if unmethylated then greater expression of pigment and if methylated less expression of pigment
What converts a B-I to a B’*
siRNAs produced from the tandem repeat of B’
What is the kti locus
locus for tyrosine kinase receptor in mice causing pigment
Kit(+) Kit (+) mice have what phenotype
wild type phenotype of solid color
Kit (+) Kit (t) have what phenotype
white feet and tail tip
The kit locus is an example of what in mice, how is it an example of this
paramutation because when crossing a Kit (+) Kit (+) with a Kit (+) Kit (t),
half of the genotypes will be Kit (+) Kit (+) and half the genotypes will be Kit (+) Kit (t)
however half of the Kit (+) Kit (+) mice will have the wild type phenotype and half will have the Kit (+) Kit (t) phenotype
Why do mice that may have the Kit (+) Kit (+) genotype express the phenotype of Kit (+) Kit (t)
miRNAs that degrade Kit mRNA passed on from parent to some progeny (Kit* allele passed on)
the differences in expression of the glucocorticoid receptors relate to
stress levels
changes in what alter expression of glucocorticoid receptors
DNA methylation differences and acetylation of histones
Methylation of DNA has what effect in mice relating to behavioral epigenetics
inhibits binding of transcription factor causing low levels of glucocorticoid
effects of this are high stress due to high corticosterone levels
Acetylation of histones has the effect in mice relating to behavioral epigenetics
reduction of deactylase inhibitor allows transcription factor to bind and glococorticoid to be expressed
effect of this is low stress due to corticosterone levels
Childhood abuse increases chance of adult…
depression, anxiety, suicide
Relationship between abuse and what
methylation of glucocortidoid receptors
low socioeconomic environment as children alters expression of
over 100 immune genes in adults
What is the growth factor that stimulated neuron connections in mice
Bdnf
Training. mice to avoid adverse stimulus did what
reduced methylation of Bdnf
Demethylated Bdnf causes
more active memory
Injecting mice with something inhibiting demethylation had what effect
lower levels of Bdnf and therefore less memory
what is the connection found in epigenetics in conjunction with alzheimers
deacetylation of histones
Vinclozolin does what and is what
mimics testosteron and binds to androgen receptors
it is an endocrine disrupter
Was increased or decreased methylation found in vinclozolin treated males
increased DNA methylation
Which X is inactivated within a cell is controlled by what
the X inactivation center
what is the process of X inactivation
- Tsix transcriped on active X
- Xist gets transcribed on silenced X
- Formation of lncRNA which coats the Xi but not Xa
- Xist RNA recruits PCR2 which produces histone modifications on Xi via methylation
Jpx does what
stimulates transcription of Xist on inactive X
How do you use enzymes to find methylated cytosines
use restruction enzymes HPAII and MSPI which cut the same CCGG cut site but HPAII will not cleave if one of the cytosines is methylated
compare results to find methylation patterns
What is bisulfate sequencing and how does it work
another way to study expression of cytosine methylation
exposure to bisulfate will convert unmethylated cytosine to uracil,
when you sequence will now register as a T
Methylated cytosine will stay the same
