W12 Epigenetics Flashcards
What is epigenetics
study of heritable changes that affect gene activity and expression
no changes to DNA sequence
what is epigenetics used for
gene expression
determines cell specialization
Is epigenetic modification reversible
yes
What are the 3 main mechanisms of epigenetics
DNA modifications
post-translation histone modifications
histone variants
What is a nucleosome
chromatin made of 147 base pairs of DNA wrapped around a histone octamer core
What proteins make up the histone octamer
2 H2A-H2B dimers
1 H3-H4 tetramer
What is the function of histone tail modifications
regulate gene expression by creating or stopping the binding of regulatory proteins
What is the histone code
code on histone tails that regulate chromatin structure
what is the histone modification for gene activation
acetylation
what is the histone modification for gene repression
trimethylation
how does acetylation increase gene expression
removes positive lysine so the DNA becomes more negative
easier for transcription factors and RNA polymerase to bind
What is DNA methylation
addition of a methyl group to the 5th carbon of cytosine
represses gene activation
What enzymes catalyse DNA methylation
DNMT1/3
What happens to gene expression when CpG islands are methylated
reduced gene expression
Where are CpG islands typically found
at promoters
What role does DNA methylation play in cancer
less expression of TSG
What is genomic imprinting
gene expression is determined by the parent of origin regulated by DNA methylation
Give an example of an imprinting disorder
Prader-Willi Syndrome
What is Prader-Willi Syndrome caused by
no active paternal genes in chromosome 15
What is X-inactivation
where one X chromosome is epigenetically silenced
How can the environment affect the epigenome
can lead to mutations in DNA
What are polyphenisms
two or more phenotypes from a genotype due to environmental factors
How does royal jelly influence honeybee development
inhibits DNMT3
less DNA methylation so genes to remain active
What is the epigenetic difference between queen bees and worker bees
Queen bees have lower DNMT3 activity
What 3 epigenetic changes due to air pollution
DNA methylation
histone modifications
miRNA expression
What happens to DNA methylation after fertilization
demethylation of genome
then re-methylation during development
Why is DNA methylation important for development
supresses unwanted genes
What is the role of CpG islands in development
remain unmethylated to regulate gene activation
What are CpG sites
C then G next to each other in the DNA seq
What is a histone deacetylase inhibitor for
prevents the removal of acetyl groups
reactivates silenced genes
What is the are miRNAs in epigenetics for
regulate gene expression post-transcription
What is an activating histone modification
Acetylation on lysine of histone tails
What is a repressive histone modification
Methylation of H3K9 or H3K27
What is the primary function of DNMT3
make new DNA methylation patterns
