An individual has sickle cell trait when one of the two copies is carrying the sickle cell beta globin gene. On the other hand, if both the copies carry sickle cell beta globin gene then the individual has sickle cell anemia and suffers from the debilitating disease. In accordance with predictable patterns of inheritance there are four possibilities:
i. An individual with normal beta globin hemoglobin genes has children with an individual possessing two copies of sickle cell gene have a 100% probability that all their children will have sickle cell trait i.e. one normal gene and one sickle cell gene.
ii. When two individuals with sickle cell trait have children then each of their offspring’s has a 50% chance of having sickle cell trait, 25% chance of inheriting normal homozygous genes i.e. two normal copies of beta globin hemoglobin gene and 25% chance of inheriting two copies of sickle cell gene.
iii. If an individual possessing normal beta globin hemoglobin genes has children with an individual having sickle cell trait then each child has a 50% chance of inheriting two copies of normal beta globin hemoglobin genes and an equal chance of having sickle cell trait.
iv. In case an individual having sickle cell trait decides to have children with an individual having sickle cell anemia then each child has a 50% chance of having sickle cell trait and a 50% chance of having sickle cell anemia. (JONES 2008).
Hemophilia is a recessive, X linked disease. therefore, genetic segregation and dominance play an important role in the inheritance of hemophilia. The recessive mutated forms of clotting factor VIII and IX are present on the X chromosome. Therefore, the disease is more common in males because they have a single X chromosome and if it has the mutated gene then the person will have hemophilia as unlike females they do not have another X chromosome for compensation.