The document discusses genes that have multiple alleles (polyallelic). It provides examples of genes with increasing numbers of alleles and the resulting combinations of genotypes. Genes involved in tissue typing and the immune system are often polyallelic, generating genetic diversity. The document uses the ABO blood group system as an example of a triallelic gene that determines antigens on red blood cells. The different blood types are determined by combinations of three alleles, and compatibility for transfusions depends on whether the donor and recipient antigens match or cause agglutination.
![Genes and their alleles ,[object Object],[object Object],[object Object],© 2007 Paul Billiet ODWS](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)