How sickle cell disease inherited?

Answer 1

Recessively, that means that both parents must be symptomless carriers then there is only a 1 in 4 chance that a given child will be born with the disease.

Note: symptomless carriers have the strong advantage of being much more likely to survive malaria than "normals". Sickle cell disease is inherited through a single pair of genes (one gene from each parent), on chromosome 11. They must receive the gene from both parents in order to actually get sickle cell disease. If they receive one gene for sickle cell disease from one parent but a normal gene from another, they have "sickle cell trait." The genes that involve sickle cell control the production of hemoglobin (a protein) in red blood cells. Abnormal hemoglobin from sickle cell disease causes red blood cells to grow incorrectly.

Persons with sickle cell trait are much more resistant to malaria (a common disease in Africa, where the gene originated) than persons having two normal genes. This makes the sickle cell gene very likely to persist in areas where malaria is endemic, like Africa.