Epigenetics Flashcards
Understand the four main characteristics of epigenetic phenomena.
Different gene expression pattern/phenotype from identical genes
Inheritance through cell division, even through generations
Like a switch: Gene is either off or on, in-between state is unstable
Erase-able (interconvertibile or interchangeable, ON or OFF w/ capacity to go from one to the other). Offers therapeutic potential! Correct a disease state
Explain the basic principle of Waddington’s epigenetic landscape.
Ball at the top of the hill with equal capacity to roll in different directions and land in different valleys. Think of it like energy states. Cell is a stable “low energy” state.
List three specific examples of epigenetic phenomena.
In nucleus: Heterochromatin domains, X-inactivation, imprinting, centromere marking by CENP-A (to label “tug” point),
In cytosol: reinforcing feedback loops involving trans-acting factors; bacteriophage lambda repressor mechanism; feedback lops in the initiation of certain cancers that operate through cytosolic signaling proteins and microRNAs
Describe how DNA methylation can be inherited through cell division.
Occurs on C of CpG; does not affect base pairing of 5meC with G
After replication, maintenance methyltransferases recognize the hemi-methylated DNA molecule and mark the new complement strand
Name three chemical modifications to DNA or histones that can potentially be inherited.
Methylation, acetylation, and deacetylation??
How can epigenetic mechanisms and inheritance occur both inside AND outside the nucleus?
When cells divide, they split the cytoplasm so anything that’s occurring stably & self-reincofcing can be inherited. e.g. malignant reinforcing loop. DOESN’T DEPEND ON TRIGGERING EVENT; self-sustaining without initial trigger being present anymore
Name a specific type of gene that, when aberrantly methylated with 5meC, can lead to cancer and an approach to therapeutic intervention in this case.
Tumor Suppressor Gene (TSG).
Combined DNA methyltransferase and histone deacetylase inhibition (because HDACs can also silence genes) to promote reactivation of TSG
