Question

what is sickle cell trait?
having abnormally shaped red blood cells in the absence of sickle cell disease
a mild form of sickle cell disease
having a single copy of the mutated beta-globin gene
having sickle cell disease due to environmental rather than genetic traits

Explanation:

Sickle cell trait is a condition where an individual has one normal beta - globin gene and one mutated (sickle) beta - globin gene. People with sickle cell trait usually do not have the symptoms of sickle cell disease. Option A is incorrect as having abnormally shaped red blood cells in the absence of sickle cell disease is not the definition of sickle cell trait. Option B is wrong because sickle cell trait is not a form of sickle cell disease. Option D is incorrect since sickle cell disease is a genetic disorder, and sickle cell trait is also related to genetics (having one mutated gene).

Answer:

C. having a single copy of the mutated beta - globin gene