Final answer:
Histone methylation, DNA methylation, and centromere determination are all part of epigenetic mechanisms because they modulate gene expression through heritable chromatin modifications without changing the DNA sequence itself.
Step-by-step explanation:
The diverse phenomena such as histone methylation, DNA methylation, and centromere determination can all be described as epigenetic because they involve heritable changes that affect gene expression without altering the DNA sequence. These changes include chromatin modifications like the methylation of histone proteins or DNA, which can influence the accessibility of DNA for transcription, and thereby regulate gene activity.
For example, histone modification can switch the 30nm fiber to a more relaxed 10nm 'beads-on-a-string' form, affecting how genes are expressed. Similarly, DNA methylation patterns, studied under methylomics, influence gene expression and these patterns can be hereditary. Epigenetic changes can respond to environmental factors and propagate through multiple cell divisions, sometimes even across generations, thereby affecting descendant cells.