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D2.2.7 (HL)—Epigenetic inheritance

Epigenetic inheritance transmits gene-expression states without DNA sequence change when tags persist through cell division or reproduction across generations and tissues.

Syllabus
First assessment 2025
Objective
D2.2.7
Level
HL

Some Epigenetic States Can Persist through Cell Division

HL only

Epigenetic inheritance passes a change in gene expression to daughter cells or offspring without changing the nucleotide sequence of DNA.

If DNA methylation or histone modifications remain in place or are re-established during chromosome replication and division, the inherited chromatin state can keep a gene active or repressed.

During mitosis, persistent tags can transmit a cell-lineage expression pattern to daughter cells. If tags remain through gamete formation and meiosis, an expression state may influence offspring.

A repressive mark maintained through repeated mitoses can help daughter cells retain the same differentiated identity even though every cell division copies the same DNA sequence.

Epigenetic inheritance is inheritance of expression state, not a change in allele sequence, and most tags are not guaranteed to persist through gamete formation.

HL Gene Expression Control

HL only
  • Transcription factors, promoters, enhancers, activators and repressors control RNA polymerase activity.
  • mRNA lifetime limits translation; poly-A shortening and nucleases help remove transcripts.
  • DNA methylation and histone modification alter chromatin access without changing base sequence, creating epigenetic patterns during differentiation.
  • The genome is all genetic information; the transcriptome and proteome vary with cell type, time and environment.
  • Some epigenetic marks persist through cell division or inheritance, although most are reset during gamete formation; genomic imprinting is an exception.
  • Hormones regulate eukaryotic transcription through receptors and transcription factors; lac and trp operons illustrate bacterial control.
  • Twin studies and environmental exposures help separate genetic, epigenetic and environmental effects on phenotype.

Concept essentials

  • Epigenetic inheritance passes expression states rather than DNA sequence changes.
  • Some DNA methylation or histone marks can persist through cell division.
  • Inherited epigenetic marks can influence gene activity in descendant cells.
  • Epigenetic inheritance is distinct from mutation of an allele.