Question

For two alleles of the same gene that demonstrate incomplete dominance, you would expect to see a __________ phenotypic ratio in the F2 generation offspring? 1) 3:1 2) 1:2:1 3) 9:3:3:1 4) 1:2

Answer 1

A 1:2:1 phenotypic ratio is expected in the F2 generation offspring for two alleles showing incomplete dominance. The presence of a recessive lethal allele would result in a 1:2:0 genotypic ratio as the homozygous recessive would not be viable.

Step-by-step explanation:

For two alleles of the same gene that demonstrate incomplete dominance, you would expect to see a 1:2:1 phenotypic ratio in the F2 generation offspring. This is because incomplete dominance results in a scenario where the heterozygous phenotype is an intermediate of the two homozygous phenotypes, rather than displaying complete dominance where one allele completely masks the other. Therefore, the correct answer to the student's question is 2) 1:2:1.

In a cross between two heterozygous individuals, the three possible genotypes that can result are homozygous dominant, heterozygous, and homozygous recessive. However, in the case of a recessive lethal allele that is expressed in utero, the homozygous recessive offspring would not survive, thus altering the expected genotypic ratio from a typical 1:2:1 to a 1:2:0 ratio, since there would be no viable homozygous recessive individuals. This distinction is crucial and highlights the impact of lethal alleles on inheritance patterns.

Learn more about Incomplete Dominance