Reappearance of Ancestral Trait

Reappearance of an ancestral trait, after several generations, is known as:

Correct Answer: Atavism

Atavism is the reappearance of an ancestral character that has been absent for several generations. It occurs when previously suppressed or silent genes (recessive alleles or dormant gene combinations) are re-expressed.

Key Facts — Atavism

• Mechanism: Re-activation of dormant recessive genes or specific gene combinations that were masked in intermediate generations.
• Example in animals: Occasional polydactyly in horses (extra toes, resembling ancestral Eohippus); striping in some horse breeds.
• Distinguished from mutation: Atavism is not a new change — it is revival of an old one.

Why Other Options Are Wrong

• Epistasis: One non-allelic gene masks expression of another — a current gene interaction, not a generational reappearance.
• Mutation: A sudden heritable change in genetic material — a new alteration, not revival of an old trait.
• Heterosis: Increased performance of offspring over parents due to heterozygosity — unrelated to ancestral trait reappearance.