A chin fissure is a dominant trait. If a homozygous-dominant father mates with a homozygous-recessive mother, what are the chances that their first child will have a chin fissure?

In genetics, dominant traits require only one copy of the dominant allele to express that trait, while recessive traits require two copies of the recessive allele. In this scenario, the chin fissure is described as a dominant trait. The homozygous-dominant father has two dominant alleles, while the homozygous-recessive mother has two recessive alleles.

The father contributes a dominant allele (let's denote it as "F") and the mother contributes a recessive allele (denote it as "f"). The possible gene combinations for their offspring would be as follows: since the father can only pass on "F" and the mother can only pass on "f," every offspring will inherit one "F" from the father and one "f" from the mother. This leads to a genotype of "Ff" for each child.

Because "F" is dominant, every child with this genotype will exhibit the chin fissure trait. Thus, there is a 100% chance that their first child, as well as any subsequent children, will have a chin fissure.

This is the reason why the answer is 100%. In terms of dominance, any child inheriting at least one dominant allele will express the dominant