In an Experiment, It Was Found That Newborn Rats Who

Multiple Choice

In an experiment, it was found that newborn rats who were genetically predisposed to be skittish, nervous, and high-strung would develop into calm, exploratory, and stress-resistant adult rats when raised by genetically unrelated, attentive mothers. Although the rats' DNA did not change, the chemicals that controlled their gene expression did change, a phenomenon called:

A) epigenetic change.
B) allele variation.
C) recessive gene mutation.
D) dominant gene mutation.