Question

Scientists are studying a genetic disorder. They discover that when both parents are carriers, and do not express the disorder themselves, their children have a 25% chance of developing the disorder. If only one parent is a carrier, none of the children express the disorder. What type of disorder are they most likely studying?

Answer 1

The scientists are most likely studying a recessive genetic disorder. In this case, both parents are carriers of the recessive gene but do not express the disorder themselves, which means they are heterozygous for the gene (one normal allele and one recessive allele).

For a child to express the disorder, they must inherit the recessive allele from both parents, resulting in a homozygous recessive genotype. In this situation, there is a 25% chance of the child inheriting the disorder (homozygous recessive), a 50% chance of being a carrier like their parents (heterozygous), and a 25% chance of inheriting two normal alleles (homozygous dominant).

When only one parent is a carrier, the probability of the child inheriting the disorder is zero because they cannot receive the recessive allele from both parents.