Question

People with achondroplastic dwarfism are heterozygous for a dominant allele conferring this trait. The homozygous dominant condition for the achondroplasia allele is lethal. What is the probability that two people with achondroplastic dwarfism will have a surviving child with this trait?

Answer 1

The allele for dwarfism - D its dominant
Recessive allele -d
If the person has heterozygous alleles -Dd the person will have achrondroplastic dwarfism
However if the person if homozygous for the allele DD it’s Lethal and person can’t survive
If both parents are Dd
Dd X. Dd
Offspring DD Dd Dd dd
Probability of children who survive with the trait have the genotype Dd
Probability - 1/4 + 1/4
Probability of having surviving children with the trait -1/2 -0.5