Freckles and Sickle Cell Disease

The Sickle Cell Disease

The sickle cell disease is a recessive condition which means that in order to have the disorder, one must have two copies of the sickle hemoglobin gene. The gene for usual hemoglobin is denoted as HbA or A while that of sickle hemoglobin is shortened to HbS or S. As such, an individual with the sickle cell disease will have two copies of the HbS gene which is represented as SS. In some cases, individuals are carriers of the HbS gene. This means that they have one copy of the sickle hemoglobin gene along with a copy of normal hemoglobin. Such an individual is said to have the sickle cell trait which is represented as AS. In this context, one parent has the sickle cell disease (SS) while the other has the sickle cell trait (AS). The offspring from the two individuals will be as follows: AS, SS, AS, and SS. As such there is a 50 percent chance that their offspring could have sickle cell disease.

Freckles and the MC1R Gene

Freckles are an observable trait which is essentially areas on the skin that contain high melanin levels. The gene responsible for the production of melanin is the MC1R gene. If the gene is recessive (f), it means that only individuals with the allele pair (ff) will have observable freckles on their skin. The case in question features a woman without freckles having a son that does have freckles. Considering the recessive nature of the gene, the only possible allele pair in the case of the mother is either FF or Ff. If the son is to have freckles, then it means that his father must carry the (f) gene in some form- Ff or ff. However, the crosses that lead to an offspring with freckles are the mother with an Ff allele and the father with either Ff or ff. With the (f) gene on both sides, there is a 1 in 4 chance that one of their offspring will have the recessive gene that causes observable freckles.