Explain how blood type is an example of
both codominance and multiple alleles.

In the hereditary pattern of Mendel's laws, there are two phenotypes, in that of incomplete dominance or three intermediate inheritance, as well as in codominance; in multiple alleles more than three phenotypes are manifested depending on the number of alleles present in the population. A typical example is the alleles of the blood group system. Multiple alleles originate from different mutations in the same gene.

Explanation:

We speak of multiple alleles when there are more than two possible alternative alleles to specify certain traits. According to the hereditary pattern of Mendel's laws, each hereditary characteristic is regulated by two alleles, in contrast to multiple alleles in which a hereditary characteristic is regulated by more than two alleles, for this reason they can only be studied in populations in where the number of individuals allows the manifestation of these characteristics, such as blood groups in the human population, which are classified according to the presence of certain chemicals that red blood cells have, called antigens. Type A blood has an antigen called A, type B blood has an antigen called B, type AB blood has the A antigen and B antigen, and type O blood has no antigen. These blood types are determined by a gene that has multiple A, B, and O alleles. The A and B alleles are codominant, while the O allele is recessive. For this reason, a person with blood type A has either two AA alleles, or one A and one O allele.

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