Human blood ABO type is an example of

📌 Concept:
-The phenomena when more than two alternate alleles of a single gene govern a character is called multiple allelism. All the multiple alleles occupy their respective loci or position on the homologous chromosomes.
-All the multiple alleles exhibit alternate traits of a single character.
-Examples of multiple allelism are: ABO blood group (3 alleles), Coat color in rabbits (4-alleles), Eye color in drosophila (12-alleles)

✅ Explanation:
-The human blood group (ABO blood group) shows multiple allelism where one character is governed by three alleles
-The ABO blood group gene I (Iso agglutinogen) is present on the 9th chromosome. Gene I has three alleles IA, IB, IO 
-IA allele forms a sugar on the plasma membrane of RBC called a-antigen.
-IB allele forms a different sugar on the RBC called b-antigen.
-IO does not form any antigen.
-Alleles IA and IB are dominant over allele IO but co-dominant to each other.
-The ABO blood grouping is used to determine the blood group of an individual based on the presence or absence of antigens A & B.

🔴Additional Information:
-Linkage: The tendency of genes present in the same chromosomes to stay together in the hereditary transmission is known as linkage.
-The genes located in the same chromosomes are called linked genes, and those present in different chromosomes are termed unlinked genes
-Polygenic Inheritance: It deals with quantitative traits such as height, weight, and number.
-It is controlled by more than one pair of non-allelic genes (Polygenes)