Ans.: A. Epigenetics"Epigenetics is defined as changes that alter the pattern of gene expression that persist across at least one cell division but are not caused by changes in the DNA code. Epigenetic changes include alterations of chromatin structure mediated bymethylation of cytoosine residues in CpG dinucleotides, modification of histones by acetylation or methylation, or changesin higher-order chromosome structure- " Harrison"