Epigenetics Flashcards
epigenetics
the study of heritable (and sometimes reversible) changes in gene function that occur WITHOUT A CHANGE IN THE SEQUENCE of DNA
*heritable meaning from one cell to its daughter cell (not necessarily parent to child)
what can regulate epigenetic modification
histone alteration and DNA methylation; regulates levels of expression of a gene
what are histone modifications
modifications of specific histone residues lead to fine-tuned gene regulation
what is DNA methylation
methylation of certain cytosine nucleotides leads to genetic repression
histone acetylation
catalyzed by histone acetlyases (HAT)
*acetylation neutralizes the positive charge of the histone
tends to form a LOOSER conformation
**leads to INCREASED gene transcription
histone de-acetylation
catalyzed by histone deacetylases (HDAC)
*positive charge
tends to bind DNA TIGHTER
**leads to DECREASED gene transcription
HDAC inhibitors
INCREASE gene expression (because normally HDACs would decrease gene expression, so inhibiting them does the opposite)
DNA methylation - overview
C’s of CpG dinucleotides are methylated by DNA methyltransferases (DNMTs: DNMT 1, 3A, and 3B)
*methylation is inversely related to gene trancription
does methylation of gene promoters increase or decrease expression
DECREASES expression (methylation is inversely correlated with gene expression)
*as methylation goes up, gene expression goes down
epigenetics and cancer
-in cancer cells, DNA in general is hypomethylated (increasing gene expression of oncogenes)
-BUT the tumor suppressor cells specifically are HYPERmethylated (decreasing expression of tumor suppressors, allowing tumor cells to proliferate and/or metastasize)
genomic imprinting
a process by which specific genes regulate allele-specific expression, based on the parent of origin
*imprints are maintained throughout an individual’s life, but may be tissue-specific
