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Epigenetics, Chromatin Modifications, and Regulation definitions

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  • Epigenetics
    Heritable changes in gene expression caused by mechanisms other than alterations in the DNA sequence, often involving chromatin structure.
  • Chromatin
    A complex of DNA and proteins that packages genetic material, influencing accessibility for gene expression.
  • Euchromatin
    A loosely packaged chromatin state that allows proteins to access DNA, enabling active gene transcription.
  • Heterochromatin
    A tightly packaged chromatin state that restricts protein access, resulting in gene silencing.
  • Chromatin Remodeling
    The repositioning of nucleosomes along DNA to expose or hide regions, such as promoters, affecting transcription.
  • Nucleosome
    A structural unit of chromatin, consisting of DNA wrapped around histone proteins, determining DNA packaging.
  • Histone Protein
    A core protein component of nucleosomes, possessing tails that can be chemically modified to regulate chromatin structure.
  • Acetylation
    The addition of acetyl groups to histone tails, generally resulting in open chromatin and increased gene expression.
  • Methylation
    The addition of methyl groups to histone tails, usually leading to closed chromatin and gene repression, but with context-dependent effects.
  • Histone Code
    The complex pattern of over 150 possible histone modifications that collectively influence gene activation or suppression.
  • Histone Variant
    A rare, non-standard histone protein found in specific chromosomal regions, potentially altering chromatin structure and gene regulation.
  • CpG Island
    A DNA region rich in unmethylated CG dinucleotides, often located near promoters and associated with active gene expression.
  • SWI/SNF Complex
    A multi-protein assembly responsible for repositioning nucleosomes during chromatin remodeling to regulate gene accessibility.
  • X Inactivation
    A process in female mammals where one X chromosome becomes transcriptionally silent, forming a Barr body to balance gene dosage.
  • Genetic Imprinting
    A phenomenon where only one parental allele is expressed due to chromosomal inactivation, impacting phenotype despite identical DNA.