When two unrelated individuals or lines are crossed, the performance of $F_1$ hybrid is often superior to both its parents. This phenomenon is called

Lethal genes are

Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino

$A$ $Y-$linked gene is responsible for hypertrichosis (long hair on ears). When an affected man marries a normal woman, what percentage of their daughters would be expected to have hairy ears?

Crossing over that results in genetic recombination in higher organisms occurs between