Presence of two copies of mutated alleles would cause sickle cell anemia in person.
Explanation:
The gene HBB codes for the beta globin protein of hemoglobin. Hemoglobin is the protein present in red blood cells and serve in oxygen transport. Mutation in HBB gene leads to production of abnormal hemoglobin molecules. These hemoglobin molecules stick to each other and impart stiffness and sickle shape to the red blood cells. Presence of two copies of mutated gene leads to sickle cell anemia characterized by reduced oxygen supply to the body cells and/or blocked blood vessels.
Darwin describes natural selection as a process whereby nature selects those organisms that have favourable characteristics to be parents of the next generation. The individuals possessing the favourable traits are better suited to the prevailing environmental conditions. This enables them to stand a better chance to survive in the struggle for existence due to limited resources.
