Question

Achondroplasia (dwarfism) is caused by a dominant allele. A woman and a man both with dwarfism marry (AaxAa). If individuals homozygous for achondroplasia (AA) are not viable (death of embryo), what would be the genotypes, phenotypes and phenotypic ratios expected in the progeny? What if a dwarf female (Aa) mates with a normal height male (aa)?

Answer 1

Answer:

Genotypes of offspring: AA, Aa, Aa and aa

Phenotypes: Possibility that 3 out of 4 offspring will have dwarfism, there is a 1 out of 4 chance that one of the offspring will be homozygous dominant for Achondroplasia and will not be viable

The phenotypic ratio is: 3:1 for the offspring having the phenotype

Explanation:

• After doing a punnet square, there is a 25% chance that one of the offspring will not inherit the Achondroplasia.

• There is a 75% chance that the offspring will inherit Achondroplasia
• There is a 25% chance that one of the offspring will be homozygous dominant (AA) and will not be viable