A woman is homozygous for a negative blood type

Many blood proteins contribute to blood type (Stratton, 1952), and the ABO protein system in particular defines which types of blood you can receive in a transfusion. An example of codominance occurs in the human ABO blood group system. Indeed, 'codominance' is the specific term for a system in which an allele from each homozygote parent combines in the offspring, and the offspring simultaneously demonstrates both phenotypes. In other words, nothing is different about the way these alleles are inherited the only difference is in the way the alleles determine phenotype when they are combined.Р”Р„s opposed to partial dominance, codominance occurs when the phenotypes of both parents are simultaneously expressed in the same offspring organism. Note, however, that partial dominance is not the same as blending inheritance after all, when two F 1 pink flowers are crossed, both red and white flowers are found among the progeny. Thus, when homozygous red flowers (A1A1) are crossed with homozygous white (A2A2), a variety of pink-shaded phenotypes result. In Figure 1, for example, neither flower color (red or white) is fully dominant. Although the offspring may show a variety of phenotypes, each one will lie along a continuum bracketed by the homozygous parental phenotypes.

When partial dominance occurs, a range of phenotypes is usually observed among the offspring. This intermediate phenotype is a demonstration of partial or incomplete dominance.

However, sometimes the heterozygote displays a phenotype that is an intermediate between the phenotypes of both homozygote parents (one of which is homozygous dominant, and the other of which is homozygous recessive). Complete dominance occurs when the heterozygote phenotype is indistinguishable from that of the homozygous parent. Dominance affects the phenotype derived from an organism's genes, but it does not affect the way these genes are inherited.

A woman is homozygous for a negative blood type