Final answer:
Histone acetylation results in loose packing of nucleosomes, allowing transcription factors to bind to the DNA and genes to be expressed.
Step-by-step explanation:
Histone acetylation refers to the addition of acetyl groups to histones, which are proteins that help package DNA into compact structures called nucleosomes. When histones are acetylated, the nucleosomes become loosely packed, making the DNA more accessible to transcription factors. This allows the transcription machinery to bind to the DNA and initiate gene expression. In contrast, deacetylation of histones promotes condensation of the chromatin and inhibits transcription.