Achondroplasia is a form of dwarfism caused by a dominant allele. The homozygous dominant genotype causes death, so individuals who have this condition are all heterozygotes. If a person with achondroplasia mates with a person who does not have achondroplasia, what percentage of their children would be expected to have achondroplasia?0%100%50%75%
Question
Achondroplasia is a form of dwarfism caused by a dominant allele. The homozygous dominant genotype causes death, so individuals who have this condition are all heterozygotes. If a person with achondroplasia mates with a person who does not have achondroplasia, what percentage of their children would be expected to have achondroplasia?0%100%50%75%
Solution
The person with achondroplasia has the genotype Aa (where A is the dominant allele for achondroplasia and a is the recessive allele for normal growth). The person without achondroplasia has the genotype aa.
When they mate, the possible combinations of alleles in their offspring are:
- Aa (from the A of the parent with achondroplasia and the a of the parent without achondroplasia)
- aa (from the a of the parent with achondroplasia and the a of the parent without achondroplasia)
So, 50% of their children would be expected to have achondroplasia (those with the Aa genotype) and 50% would not (those with the aa genotype). Therefore, the answer is 50%.
Similar Questions
Achondroplasia is a dominantly inherited condition with a phenotype that includes a large head and short stature. It is caused by mutations in the gene for fibroblast growth factor receptor 3 (FGFR3), which causes the receptor to be active even when its ligand is not present. Compared to individuals without achondroplasia, individuals who are heterozygous for this condition most likely:A.do not have the achondroplasia phenotype because expression of the wild-type receptor masks the expression of the mutant receptor.B.have the achondroplasia phenotype because having one copy of the mutant receptor causes the receptor to be inappropriately activated.C.have an intermediate phenotype between wild-type and achondroplasia because both wild-type and mutant receptors are expressed.D.do not have the achondroplasia phenotype because only the wild-type receptor is expressed.
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