Looking for the causes of the sickle-cell anemia in the human (Fig. 2–28)
Ingram (1956, 1957) has established that it is due to differences in hemoglobin
composition. Normal erythrocytes contain hemoglobin A (HbA) while the
sickle-cell ones contain the pathological hemoglobin (HbS) in which glutamine
in the polypeptide chain is replaced by valine. The presence of HbS leads to
deformation of the erythrocytes, aggregation, thrombus formation and all
syndromes typical of the sickle-cell anemia.
image
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Figure 2–28. Sickle-cell anemia in man (From Stent, 1974). A — micrograph of erythrocytes from a patient with sickle-cell anemia (at low oxygen pressure); B — micrograph of erythrocytes from a healthy man (under the same conditions).
These are great achievements of molecular biology and genetics. They
show the way for the study of the gene at the molecular level which is
undisputedly the only one possible. It must be noted however, that there is