Chapter 11.8 Flashcards
Epigenetics
Genetic modifications that alter the expression of a gene without changing the nucleotide sequence. These changes are reversible and heritable
What is a epigenome and what is unique about it?
It’s the epigenetic state of the cell, and can change many times over a lifespan due to environmental factors
Heterochromatin
Tightly packed genes in a chromosome that are unavailable for transcription and are not expressed
Euchromatin
Loosely packed genes in a chromosome that are available to transcribe and therefore expressed
Epigenetic changes vs genetic changes
Epigenetic: affect how your body reads a DNA sequence without altering the sequence of DNA bases. It instead can change the marks on DNA, changing proteins. Can be caused by environment. Can be reversed.
Genetic: Permanent alterations to the DNA bases. Aka mutations.
DNA methylation
Adds methyl groups to DNA backbone which slows down transcription, which therefore decreases or halts gene expression. The methylation state of a gene is copied every time DNA is replicated
How can epigenetic modifications be made? (How are they reversible?)
These changes come from manipulating histone proteins and DNA
Histone acetylation
When acetyls are added to histone, which pull the tightly packed DNA strand away from histone which makes it looser. This loosely packed DNA can now be transcribed. Adding and taking away acetyls can turn off and on a gene.
Are all cells genetically identical?
Yes. All cells in the body have the same chromosomes and therefore the same genes. Just some genes are turned off and on depending on the cell type. This is due to producing different protein products and different mRNAs
Monoallelic expression
Only one allele is expressed. The other is silent. Three main types.
1) Genomic imprinting (when only one copy of a gene from the mom or dad is expressed) occurs via methylation. If a gene is “imprinted” then it is turned off
2) random inactivation of one X chromosome in females
3) Randomly generated allele inactivation
