Red Blood Cells in Standard versus Sickle-Cell phenotypes
Hemoglobin is a
tetrameric molecule formed from two Alpha and two Beta chain subunits.
Hemoglobin with two standard
Beta-chain alleles (AA)
is a globular protein. When two sickle-cell
Beta-chain alleles (SS)
are present, reduced oxygen tension
in the blood causes the hemoglobin
molecule to undergo a conformational shift to a crystalline form.
The formation of large crystals distorts the shape of the red blood
which causes blockage of small capillaries and results in acute,
infarctive crises. The sickle cells are also more easily broken,
which results in anemia.