Alleles can be described as 1. dominant 11. recessive III. codominant IV. partially dominant V. incompletely dominant O A. I, II, III, and V only OB. I and II only OC. I, II, and Ill only OD II, III, and V only

A. I, II, III, and V only

Explanation:

In genetics, an allele refers to the specific form of a gene, which encodes traits. These alleles are usually in pairs in a diploid organism i.e. an organism with two sets of chromosomes. According to Gregor Mendel,

- An allele can either be DOMINANT when the allele masks the phenotypic expression of its allelic pair while the allele that is masked is said to be RECESSIVE.

- Two alleles can also be CO-DOMINANT when the two alleles are neither dominant or recessive over one another but are simultaneously expressed in that particular gene.

- Alleles can also be INCOMPLETELY DOMINANT when one allele is not completely dominant over the other, hence, forms a third intermediate phenotype when in combination with the second allele i.e. in an heterozygous state.

Based on this, an allele can be dominant (I), recessive (II), codominant (III), and incompletely dominant (V).