Thalassemias

Question 1

What are the thalasemias?

Answer 1

A group of disorders due to defective and imbalanced globin prouction

Question 2

How are thalassemias classed?

Answer 2

According to which globin chain/s are affected

• alpha
• beta
• ab
• egdb

Question 3

Describe the Alpha thalassemias. Origin and types

Answer 3

These are the result of more than 80 deletions/point mutations of the genes which encode the alpha chain of Hb. There are 2 types.
A+ is characterised by a partial defect in a-globin production (only one allele affected)
A0 is characterised by a complete defect in a-globin production (both alleles affected

Question 4

Describe Beta thalassemias - origin

Answer 4

These are the result of over 200 different mutations in the b-globin gene resulting in phenotypes

Question 5

Beta thalassemia phenotypes

Answer 5

B0 no globin gene product
B+ strongly reduced levels of b-globin production
B++ mildly reduced levels of b-globin production

Question 6

Alpha and Beta thalassemias are proposed to confer heterozygous advantage against…?

Answer 6

P. falciparum Malaria

Question 7

Different populations have different sets of mutations for thalassemias. How does this occur

Answer 7

Individual mutations arose locally and then expanded because of selective advantage