However, certain genetic diseases are more common in some populations than others and natural selection can explain this variation.

Evolutionary theory predicts that deleterious conditions will be selected out of populations and, therefore, occur at a very low rate. However, certain genetic diseases are more common in some populations than others and natural selection can explain this variation. Using Tay-Sachs or sickle-cell anemia as your example, explain why these diseases are more common in some populations than others. Be specific. 2-3 substantial paragraphs.