Epigenetic modification
Chemical tags on DNA or on the histone proteins it wraps around that change how active a gene is, without changing the DNA letters. DNA methylation usually switches genes off.
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Analogy
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In practice
X-chromosome inactivation in female mammals silences one X chromosome in each cell using these tags.
Practice
Flashcards
- What does DNA methylation usually do?It switches genes off, without changing the DNA sequence.
Questions people ask
Can epigenetic changes be inherited?
Within the body, yes: when a cell divides, the tags are copied, so daughter cells keep the same gene activity. Passing them across generations is less common. Most tags are wiped in the egg and sperm. Evidence in mammals is limited, and scientists still debate how much is passed on.
What do histones do?
Histones are proteins that DNA winds around, like thread on a spool. Together they form chromatin. Tight winding makes genes hard to read. Loose winding makes them available. Chemical tags on histones, such as acetyl groups, help control how tight the winding is.