Question

What is the typical ratio of stance phase to swing phase during normal walking?

A) 1:1
B) 2:1
C) 3:2
D) 1:2

Answer 1

In a mating between two heterozygous individuals for a recessive lethal allele, the expected genotypic ratio in the living offspring would be 1:2:0 (homozygous dominant: heterozygous :homozygous recessive) because the homozygous recessive offspring do not survive.

Step-by-step explanation:

When two individuals that are heterozygous for a recessive lethal allele mate, the expected genotypic ratio observed in the offspring significantly differs from the typical 1:2:1 Mendelian ratio because the lethal allele causes death in utero for homozygous recessive individuals. Since the homozygous recessive individuals do not survive to be born, we will see only the homozygous dominant and heterozygous offspring.

The correct genotypic ratio, given that one-fourth of the potential offspring die in utero due to the lethal allele, would be 1:2 for the surviving offspring. This means out of three surviving offspring, on average one would be homozygous dominant, and two would be heterozygous. Therefore, expected genotypic ratio is 1:2:0 rather than 1:2:1, as the homozygous recessive (1:1) individuals are not viable.