Thalassemia occurs due to which mutations –a)  Missenseb)  Splicingc)  Transitiond)  Frame–shifte)  Truncation
Thalassemia syndrome                                                                                                  

Adult hemoglobin is a tetramer, composed of two a globin chains and two β globin chains.
Thalassemia is an inherited autosomal recessive disorder.
In Thalassemia, the gentic defect results in reduced synthesis of one of the globin chains of hemoglobin.
β- Thalassemia is caused by deficient synthesis of β-chain with normal α-chain synthesis.
α- thalassemia is caused by deficient synthesis of α-chain with normal (β-chain synthesis.
Molecular defect in pathogenesis of thalassemia.

A) β-thalassemia

Most common type of genetic abnormality in (-thalassemia is point mutation, i.e. nonsense.
Some may also. occur due to deletion or insertion i.e. framshift mutations.
Defect may occur at different steps of β-chain synthesis -

i)    Splicing mutations

Mutations leading to aberrant splicing are the most common cause of β-thalassemia. 10 Chain terminator mutations
This cause premature termination of mRNA translation.
iii) Promoter region mutations
This results in transcription defect

B) α-thalassemia

The most common cause of reduced α-chain synthesis is the deletion of α-globin genes.
Rarely nonsense mutation may also cause α-thalassemia.
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