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Medicine

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Hematology

Question
2 out of 11
 

The primary defect which leads to sickle cell anemia IS (AIIMS May 2011)



A An abnormality in porphyrin part of hemoglobin

B Replacement of glutamate by valine in B-chain of HbA

C A nonsense mutation in the B-chain of HbA

D Substitution of valine by glutamate in the A chain of HbA

Ans. B

Replacement of glutamate by valine in B-chain of HbA

It is a autosomal recessive condition.

This is a haemolytic anemia resulting from the homozygous inheritance of a gene which causes an amino acid substitution in the hemoglobin molecule (beta – 6 glutamate valine) creating HbS due to point mutation.

HbS (Beta 6 glue Valine)

HbC (Beta 6 glue Lysine)

HbE (Beta 26 glue Lysine)

Extra Edge: Sickle cell disease is caused by a mutation in the beta gene

Classification

1. Homozygote (SS) – sickle cell anemia

2. Heterozygote (AS) – sickle cell trait (protects from falciparum malaria).

Symptomatic sickling occurs in homozygotes. Heterozygotes are asymptomatic, and present with mild anemia except in situation of hypoxia, Anaesthesia, when veno-occlusive events occur.

Hematology Flashcard List

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