Interactions among not allelic genes
Date: 2015-10-07; view: 368.
Inheritance of blood groups
Multiple alleles
THE BASIC THEORETICAL ITEMS OF INFORMATION
Many genes have more than two alleles (even though any one diploid individual can only have at most two alleles for any gene), such as the ABO blood groups in humans, which are an example of multiple alleles. Multiple alleles result from different mutations of the same gene. Coat color in rabbits is determined by four alleles. Human ABO blood types are determined by alleles A, B, and O. A and B are codominants which are both dominant over O. The only possible genotype for a type O person is OO. Type A people have either AA or AO genotypes. Type B people have either BB or BO genotypes. Type AB has only the AB (heterozygous) genotype. The A and B alleles of gene I produce slightly different glycoproteins (antigens) that are on the surface of each cell. Homozygous A individuals have only the A antigen, homozygous B individuals have only the B antigen, homozygous O individuals produce neither antigen, while a fourth phenotype (AB) produces both A and B antigens.
| Groups of blood | Antigens (agglutinogenes of erythrocytes) | Antibodies (agglutinins of plasma) | Genotypes |
| I (0) | no | Io | |
| II (A) | A | IA | |
| III (B) | B | IB | |
| IY (AB) | A, B | no | IA, IB |
There are some types of gene interaction. Among them are complementary genes, epistasis, polygenes (multiple or cumulative genes), and effect of position.
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| STUDY 25 | | | Complementary genes A – black colour and B – albino colour in case of genotype A_B_ are realized as agouti mouse. |