Question

Heterozygotes at the sickle-cell locus produce both normal and abnormal (sickle-cell) hemoglobin (see Concept 14.4). When hemoglobin molecules are packed into a heterozygote's red blood cells, some cells receive relatively large quantities of abnormal hemoglobin, making these cells prone to sickling. In a short essay (approximately 100–150 words), explain how these molecular and cellular events lead to emergent properties at biological organization's individual and population levels.

Short answer

At the molecular level, hemoglobin tetramer has the normal distribution of both forms of hemoglobin, such as normal (A) and sickle-cell (S).

Step-by-step solution

Heterozygous individuals

The individuals that havetwo distinct allelesinherited from each parent are called heterozygous individuals.

The alleles for hair color, such as red and brown hair, are an example of the heterozygous organism.

Sickle-cell anemia

Thered blood cell disorderin which oxygen-carrying protein (hemoglobin) gets affected due to thecrescent shape of erythrocytes (RBCs)is called sickle-cell anemia.

In sickle-cell disease, healthy RBCs become hard and sticky; this shape does not allow them to move through blood vessels and get stuck in the blood vessel, resulting in clogging of blood flow.

Emergent Property

The property found in a system at a higher organization level in which individual units do not possess those characteristics is called emergent property.

There are approximately 250 hemoglobin molecules found in the erythrocytes (RBCs). The hemoglobin molecule comprisesfour globin chains; these structural subunits make hemoglobin a tetramer at the molecular level.

The hemoglobin tetramer bears four oxygen molecules, and these subunits cooperate to increase hemoglobin affinity.

The combinations that form from the distribution of hemoglobin in RBCs are AA, AS, and SS. The number of sickle cells is more than the RBCs with normal hemoglobin, resulting in RBCs distortion.