Both parents with curly hair and freckles, and the daughter with straight hair and no freckles.

Both parents with curly hair and freckles, and the daughter with straight hair and no freckles. Their daughter married a young man with curly hair and freckles. The mother of a young man with straight hair and no freckles. What kind of children can be expected in a young family and what is their probability?

Since the daughter shows signs that are not characteristic of either of the parents, it should be concluded that curly hair dominates over straight hair, the presence of freckles over their absence, as well as the heterozygosity of both parents for both characteristics.

Let’s designate the gene that causes the development of curly hair in humans as K, then the gene for straight hair will be k. Let’s designate the gene for the presence of freckles as L, then the gene for their absence will be l.

A daughter with straight hair, who does not have freckles, will have the kkll dihomozygous genotype, because only if the genotype is homozygous can recessive traits be realized phenotypically. This girl produces eggs of the same type – kl.

The boy’s mother also had the kkll genotype and produced kl eggs. She could pass on to her son only genes for recessive traits, therefore, he is heterozygous for both traits – KkLl. This young man produces four types of sperm – kl, KL, Kl, kL.

The possible offspring of this married couple includes the following options:

children with straight hair without freckles (kkll) – 25%;

children with curly hair and freckles (KkLl) – 25%;

children with curly hair without freckles (Kkll) – 25%;

children with straight hair and freckles (kkLl) – 25%.