Methylation changes not a single letter of the DNA sequence; it simply tags the CpG island at a promoter and pulls the chromatin shut, so the transcription machinery can no longer squeeze in. Histone acetylation does the reverse, loosening the chromatin fibre and letting the gene speak again, so the two marks are opposite ends of one switch. The same genome keeps the muscle gene MYOD1 on in a muscle cell and off in a neuron, and the only difference is the layer of marks laid over it; reprogramming wipes that layer clean.
Methylation changes not a single letter of the DNA sequence; it simply tags the CpG island at a promoter and pulls the chromatin shut, so the transcription machinery can no longer squeeze in. Histone acetylation does the reverse, loosening the chromatin fibre and letting the gene speak again, so the two marks are opposite ends of one switch. The same genome keeps the muscle gene MYOD1 on in a muscle cell and off in a neuron, and the only difference is the layer of marks laid over it; reprogramming wipes that layer clean.
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