Principles of Inheritance and Variation Question 34
34. When two unrelated individuals or lines are crossed, the performance of $F_1$ hybrid is often superior to both parents. This phenomenon is called:
[2011]
(a) heterosis
(b) transformation
(c) splicing
(d) metamorphosis
Show Answer
Answer : a
Hints & Solution
(a) Heterosis or hybrid vigor occurs when two unrelated individuals or lines are crossed, the performance of $F_1$ hybrid, which is often superior to both the parents. Heterosis is quantified on an individual or population basis as the difference in the performance of the hybrid relative to the average of the inbred parents (termed the midparent value). For quantitative genetic analysis, the deviation of the hybrid relative to the midparent is the relevant value.
