Jill has light eyes and her husband Jack has dark eyes. All of their ten children have dark eyes. What is Jack's genotype?

Jack's genotype is homozygous dominant.

It can be written as BB

Step-by-step explanation

A homozygous dominant genotype is one in which both alleles are dominant.

An organism with two dominant alleles for a trait is said to have a homozygous dominant genotype. Using the eye color example, this genotype is written BB. An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype.

If the test cross results in only phenotypically dominant offsprings, then the parent organism is homozygous dominant for the allele in question.