Though Sickle Cell Anemia Is Frequently Lethal for Individuals Who

question 42

Multiple Choice

Though sickle cell anemia is frequently lethal for individuals who are homozygous for the sickle cell allele, natural selection seems to have maintained that allele in certain geographic locations.A likely explanation for this observation is

• A)the forward mutation rate to sickle cell is much higher in those regions.
• B)individuals with sickle cell anemia live longer and have more children.
• C)reversion from sickle cell to wild type is prevented in some populations.
• D)individuals who are heterozygous for the sickle cell allele are protected from malaria.
• E)only certain populations have been tested for the presence of the sickle cell allele.

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Definitions:

Superior Vena Cava

A major vein carrying deoxygenated blood from the upper half of the body to the heart's right atrium.

Thorax

The part of the body located between the neck and the abdomen, enclosing the chest and containing the heart and lungs; it is protected by the rib cage.

Velocity

A vector quantity that denotes the rate of change of position of an object, with both magnitude and direction.

Blood Flow

Blood flow is the circulation of blood through the cardiovascular system, delivering oxygen and nutrients to tissues and removing carbon dioxide and wastes.