Final answer:
Among the epigenetic modifications listed, acetylation of histones is associated with increased gene activity because it leads to a relaxed chromatin structure that allows for better access by transcriptional machinery. Therefore, the correct answer is 1) Acetylation of histones.
Step-by-step explanation:
Epigenetic Modifications and Gene Activity
The regulation of gene activity in cells involves various epigenetic modifications of DNA and histone proteins. Among the chemical modifications mentioned, acetylation of histones is associated with increased gene activity. This is because the addition of acetyl groups to histone tails by histone acetyltransferases reduces the positive charge on histones, leading to a less compact chromatin structure. This relaxed structure allows transcriptional machinery better access to DNA, thus facilitating gene transcription.
On the other hand, methylation of DNA generally suppresses gene activity by attracting proteins that condense the chromatin, making it less accessible for transcription. Similarly, histone methylation can have varying effects on gene activity, depending on which amino acids in the histone tails are modified. Phosphorylation of histones and other proteins involved in gene regulation can also influence gene activity, although this effect is context-dependent.
Considering the options provided and the processes described, acetylation of histones corresponds with increased access to the DNA and enhanced gene activity. Therefore, the correct option for the modification associated with increased gene activity is 1) Acetylation of histones.