Having a chin dimple (cleft chin) is dominant over having no chin dimple. Having long eyelashes is dominant over having short eyelashes. Jack and Jill are both heterozygous for a chin dimple and long eyelashes. What are the chances that their baby will have no chin dimple and short eyelashes?

We know that alleles are genes that occupy the same place (locus) in homologous chromosomes. They can also be defined as the alternative form of a gene, since they determine the same trait, but not in the same way. These alleles can be both dominant and recessive and assume dominance or recessive relationships in somatic cells, in which the alleles appear in pairs. The alleles responsible for the dimple in the chin and long eyelashes have a dominant character, which is one that is phenotypically expressed under homozygous (VVVV) and heterozygous (VvVv) conditions.

Knowing this, we can conclude that a heterozygous couple (VvVv) with a slit chin and short lashes have a 1 in 16 chance that their child will not have dimples in the chin and long lashes. For this couple's son not to have the characteristics shown above, he would have to have the recessive homozygous alleles (vvvv), if you make the punnet square with the parents alleles, you will see that the "aaaa" alleles only appear once in 16 possibilities.