<h2>The correct answer is explained below:</h2>
Explanation:
- According to the question, achondroplasia, a form of dwarfism, is caused by a mutant allele of the fibroblast growth factor receptor (FGFR) encoding gene.
- This achondroplasia trait is dominant in nature. This is because presence of a single copy of the mutant allele results in the development of a dwarf phenotype.
- Let the dominant mutant allele for the trait be represented by: A.
- Let the recessive normal allele for the trait be represented by: a.
- The individual with aa genotype is normal.
- The individual with Aa genotype shows dwarfism.
- The individual with AA genotype dies before birth.
- As per the question, two people having achondroplasia have the genotype Aa.
- Gametes produced by each of the individuals are, A and a.
- Mating these individuals, we get the following possible offspring,
A a
A AA Aa
Phenotype Dies Dwarf
a Aa aa
Phenotype Dwarf Normal
- The genotypes and the phenotypes of the possible offspring are represent in the Punnett square above.
- The probability of the child to have achondroplasia is:
.
- Since the child with AA genotype dies before birth so three (genotypes Aa and aa) out of four possible children survives.