COMPLEMENTARY GENES

=Complementary Genes= Complementary genes are genes that both contribute to a single characteristic, where both genes can mask the effect of the other. You may also think of complementary genes as any instance in which dominant forms of both genes are required for the dominant characteristic to be seen. [image:http://i.imgur.com/6btXG7u.png] At least one dominant allele for both Gene A and Gene B is required if any colour is to be produced; thus an individual must be A_B_ to have the black phenotype. If the individual is missing a dominant allele for either one of the two genes, they will be albino. As a result, there are only two possible phenotypes; Black and Albino. In a heterozygous cross (AaBb x AaBb) the following offspring are produced: [image:http://i.imgur.com/8q69vLk.png] Note that although six of the albino individuals have a dominant allele, for one of the two genes, they lack a dominant version of the other gene which is also required for any colour to be produced. Thus the final phenotypic ratio for Complementary genes is always: === 9 : 7 ===