Inheriting
Beta Thalassemia
Beta Thalassemia results from a mutation on the HBB gene in Chromosome 11 which is responsible for coding beta globin proteins.
However, the degree to which someone is affected by Beta Thalassemia depends on the severity of the mutation itself.
Understanding
Alleles
β - Normal beta globin allele.
β+ - Beta globin allele with moderate mutation (non deletion form.)
βo - Beta globin allele with complete mutation (deletion form.)
β+ - Beta globin allele with moderate mutation (non deletion form.)
βo - Beta globin allele with complete mutation (deletion form.)
GENETIC DESCRIPTION:
Only one of the β globin alleles bears a mutation. POSSIBLE GENOTYPES: β+/β or βo/β |
GENETIC DESCRIPTION:
Both of the β globin alleles bears a mutation. POSSIBLE GENOTYPES: βo/βo |
Inherited in an
Autosomal Recessive
Manner
Autosomal recessive inheritance means that a child will only develop or display the disease when two copies of an abnormal gene are present. Beta thalassemia is unique in this manner because when one copy of the gene is present, it is possible for the child to develop beta-thalassemia minor.
Example 1:
A mother and a father are both carriers for the beta-thalassemia trait. 25% : Child has beta-thalassemia major. 50% : Child has beta-thalassemia minor. 25% : Child has no disease or trait. |
Example 2:
One parent is a carrier and one parent does not carry the trait. 50% : Child has beta-thalassemia minor. 50% : Child has no disease or trait. |