Thalassemia occurs due to which mutations -

Ans. is 'b' i.e., Splicing Thalassemia syndrome o Adult hemoglobin is a tetramer, composed.of two a globin chains and two 13 globin chains. o Thalassemia is an inherited autosomal recessive disorder. o In Thalassemia, the gentic defect results in reduced synthesis of one of the globin chains of hemoglobin. o - Thalassemia is caused by deficient synthesis of 13-chain with normal a-chain synthesis. o a - thalassemia is caused by deficient synthesis of a-chain with normal 13-chain synthesis. o Molecular defect in pathogenesis of thalassemia. A) 13-thalassemia o Most common type of genetic abnormality in 13-thalassemia is point mutation, i.e. nonsense. o Some may also occur due to deletion or inseion i.e. framshift mutations. o Defect may occur at different steps of [3-chain synthesis - I') Splicing mutations Mutations leading to aberrant splicing are the most common cause of (3-thalassemia. ii) Chain terminator mutations This cause premature termination of mRNA translation. iii) Promoter region mutations This results in transcription defect B) a-thalassemia o The most common cause of reduced a-chain synthesis is deletion of a-globin genes. o Rarely nonsense mutation may also cause a-thalassemia.