Epigenetics, Genomic Imprinting and Mitochondrial Inheritance Quiz

See Section. Option C is correct: epigenetic regulation changes gene use without changing DNA base sequence. Chemical marks on DNA and on histones, the proteins around which DNA is wrapped, can make a gene more or less accessible. DNA methylation adds small methyl groups to DNA, while histone modifications alter the surrounding packaging. These changes help cells with much the same genome use different sets of genes, so a neurone behaves differently from a liver cell. Some regulatory states persist when cells divide, helping daughter cells retain their specialised identity. A useful distinction is that mutation changes the written instructions, whereas epigenetic regulation changes how those instructions are read.

A change in the order of DNA bases (D) alters the instructions themselves and is a mutation. B confuses inheritance between daughter cells with inheritance between generations: much of the epigenome is reset during reproduction. Transcription factors, proteins that bind regulatory DNA and influence transcription, still matter (A); epigenetic marks affect whether they can reach and use their target sequences. E wrongly limits the process to the germ line, the cells that form eggs or sperm, even though epigenetic regulation also maintains the identities of ordinary body cells.