We can say that the alleles have an additive effect on the phenotype. ABO blood type inheritance. Blood type is controlled by three alleles of one gene - I<o>, I<A>, I<B> (such marking of allelic genes can be used in the writing of genet

The phenotype of a trait determined by additive alleles depends on how many of the allele the person inherits. The more of the allele a person inherits, the more intense the phenotype will be.

If the traits you are using are dominant or recessive, this trait will "overpower" the recessive trait and will be expressed. E.g. Tt Recessive trait: Signified by small case letter-e.g. t. An organism with a recessive allele for a particular fo