An Experiment Found That Newborn Rats Who Were Genetically Predisposed

Multiple Choice

An experiment found that newborn rats who were genetically predisposed to be calm and stress-resistant grew up to be nervous, high-strung, and easily stressed adult rats when raised by genetically unrelated, inattentive mothers. These results showed that:

A) the rats' DNA changed because of their upbringing.
B) epigenetic changes had changed their brain chemistry and literally reprogrammed their future behavior.
C) severe genetic mutations had taken place from one generation to the next.
D) the rats' DNA was damaged by environmental factors, such as exposure to ultraviolet light, radiation, or chemical toxins.