Natural Selection Can Maintain Genetic Variation by Favoring Heterozygous Genotypes

question 53

Essay

Natural selection can maintain genetic variation by favoring heterozygous genotypes. In equatorial Africa, the best genotype to have for hemoglobin is heterozygous (HbA / HbS). In the United States of America, there is no advantage to the heterozygous genotype. HbA codes for normal hemoglobin, whereas HbS codes for an abnormal hemoglobin that causes red blood cells to become distorted in shape (sickle cell). Explain why the heterozygous state is advantageous in Africa, but not in the USA. What has happened to the sickle cell allele in Africa? What has happened to the sickle cell allele in the United States?

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Definitions:

Preventable Cause

A preventable cause refers to a factor or condition that can be avoided to prevent a disease, accident, or other undesirable outcomes.

Disease

A condition that disrupts normal physiological functions, often characterized by specific signs and symptoms, and can be caused by factors such as pathogens, genetic mutations, and environmental stress.

Swim Bladders

Air-filled sacs in some fish that help control buoyancy and maintain stability in the water.

Ventilation

The process of moving air in and out of the lungs to exchange oxygen and carbon dioxide.