Which of the following is a form of epigenetic alteration?

DNA methylation is indeed a significant form of epigenetic alteration. It involves the addition of a methyl group to the DNA molecule, typically at the cytosine residues of CpG dinucleotides. This modification can influence gene expression without altering the underlying DNA sequence. Methylation generally leads to gene silencing, as it can prevent the binding of transcription factors and other proteins that are necessary for gene activation, thus playing a crucial role in regulating various biological processes including development, cellular differentiation, and response to environmental factors.

In contrast, point mutations, gene amplification, and chromosomal inversions are not classified as epigenetic changes. Point mutations involve alterations in the nucleotide sequence of DNA, which directly changes the genetic code. Gene amplification refers to the increase in the number of copies of a specific gene, resulting in overexpression, while chromosomal inversion involves the rearrangement of sections of chromosomes, which can also affect gene expression but does so through changes in the genetic structure itself. Therefore, DNA methylation stands out as a key mechanism of epigenetic regulation.