Epigenetics Cheat Sheet

The core ideas of Epigenetics distilled into a single, scannable reference — perfect for review or quick lookup.

PiqCue — piqcue.com/epigenetics/cheatsheet

Quick Reference

DNA Methylation

The addition of a methyl group to the cytosine base in DNA, typically at CpG dinucleotides. Methylation of gene promoter regions generally suppresses gene transcription by blocking transcription factor binding or recruiting repressive protein complexes.

Histone Modification

Chemical modifications to histone proteins, including acetylation, methylation, phosphorylation, and ubiquitination, that alter how tightly DNA is wound around histones and thus control gene accessibility.

Chromatin Remodeling

The dynamic restructuring of chromatin architecture by ATP-dependent remodeling complexes that slide, eject, or restructure nucleosomes, thereby regulating access to DNA for transcription, replication, and repair.

Genomic Imprinting

An epigenetic phenomenon in which certain genes are expressed in a parent-of-origin-specific manner. One allele is silenced through DNA methylation depending on whether it was inherited from the mother or father.

X-Chromosome Inactivation

The process in female mammals by which one of the two X chromosomes is transcriptionally silenced to achieve dosage compensation with males. The non-coding RNA XIST coats the inactive X chromosome and recruits silencing complexes.

CpG Islands

Regions of DNA with a high frequency of cytosine-guanine dinucleotides, often located near gene promoters. CpG islands are typically unmethylated in normal cells, allowing gene expression, and their aberrant methylation can lead to gene silencing.

Non-Coding RNA Regulation

Regulatory RNA molecules, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and small interfering RNAs (siRNAs), that influence gene expression through epigenetic mechanisms without being translated into protein.

Transgenerational Epigenetic Inheritance

The transmission of epigenetic marks from one generation to the next without changes in DNA sequence, potentially allowing environmental exposures in parents to influence gene expression and phenotype in offspring.

Epigenetic Reprogramming

The genome-wide erasure and re-establishment of epigenetic marks that occurs during two critical periods: early embryonic development after fertilization and during the formation of primordial germ cells.

Environmental Epigenetics

The study of how external factors such as diet, toxins, stress, and social environment can alter epigenetic marks and gene expression, potentially leading to lasting changes in phenotype and disease susceptibility.

Key Terms at a Glance

5-Hydroxymethylcytosine (5hmC):An oxidized form of 5-methylcytosine produced by TET enzymes, serving as an intermediate in active demethylation.

5-Methylcytosine (5mC):A methylated form of cytosine in DNA, the primary epigenetic mark in DNA methylation.

Barr Body:The condensed, transcriptionally inactive X chromosome visible in the nucleus of female mammalian cells.

Bivalent Domain:A chromatin region carrying both activating and repressive histone marks, found at developmental gene promoters in stem cells.

Chromatin:The complex of DNA, histone proteins, and associated molecules that packages genetic material in the eukaryotic nucleus.

Chromatin Remodeling:The dynamic restructuring of chromatin by ATP-dependent complexes that alter nucleosome positioning and DNA accessibility.

CpG Dinucleotide:A cytosine followed by a guanine in the DNA sequence, connected by a phosphodiester bond. The primary site of DNA methylation.

CpG Island:A region of DNA with high CG dinucleotide frequency, typically unmethylated and found near gene promoters.

DNMT (DNA Methyltransferase):An enzyme that catalyzes the addition of methyl groups to cytosine bases in DNA.

Dosage Compensation:A mechanism ensuring equal expression of X-linked genes between sexes, achieved through X-inactivation in mammals.

Enhancer:A regulatory DNA element that can increase transcription of a target gene, often marked by H3K4me1 and H3K27ac histone modifications.

Epigenetic Drift:The gradual divergence of epigenetic patterns over time, contributing to differences between identical twins as they age.

Epigenome:The complete set of epigenetic modifications across the entire genome of a cell.

Euchromatin:Open, loosely packed chromatin associated with active gene transcription.

Genomic Imprinting:Epigenetic marking of genes for parent-of-origin-specific expression.

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