The genetics of a-thalassemia are similar to narrow sense heritability in that there is a gradation of phenotype, with each allele seeming to contribute equally to the trait. However, there are also differences from narrow sense heritability. In particular, as you can see from your answers above, it is difficult to predict offspring phenotype based only on parental phenotype. What two aspects of HBA1 and HBA2 combine to offset what would otherwise appear to be narrow sense heritability of a-thalassemia?

In strict mode, the narrow-sense heritability is the proportion of the additive genetic variance that contributes to the total of the phenotypic variance. This value can be associated with the inheritance of the a-thalassemia .

Explanation:

A-thalassemia is a genetic disorder caused by mutations affecting four different genes that encode alpha-globin, thus affecting the hemoglobin production process and, consequently, oxygen transport. The mode of inheritance of the a-thalassemia may be associated with narrow sense heritability since the phenotype is manifested by gradation, i.e., each allele might contribute in similar mode to this genetic condition.

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answer///multiple alleles;