What type of defect causes sickle cell anaemia

Sickle cell anaemia

• Autosomal recessive disease
• Transmission − From parent to offspring when both parents are carriers of disease
• Pair of alleles Hb^A and Hb^S controls the expression of this disease.
  Hb^A and Hb^A − Normal
  Hb^A and Hb^S − Carrier of disease
  Hb^S and Hb^S − Diseased
• Cause of the disease − Change in gene causes the replacement of GAG by GUG leading to the substitution of Glu by Val at sixth position of beta globin chain of haemoglobin.
• The mutant haemoglobin so formed polymerises at low oxygen tension, resulting in change in shape of RBC to sickle-like.