Lethal genes - Thalassemia in humans, a hereditary blood disease

Thalassemia is a hemoglobin defect in humans occurring in 2 forms. Thalassemia minor is a condition in which erythrocytes are small [microcytic] and in increased numbers [polycythemic]. The health of the individual is essentially normal. Thalassemia major is characterized by severe anemia, enlargement of spleen, microcytes and polycythemia among other symptoms early in life. The individual dies before reproductive age.
Thalassemia major is found as homozygotes [TmTm], Thalassemia minor as heterozygotes [TmTn] and normal individuals as homozygotes [TnTn]. Since all T. major individuals die before sexual maturity.

a) What proportion of adult F1 from marriages between T. minor and normal would be normal?

b) What proportion of F1 adults from marriages between two T. minor would be anemic?