Recessive Alleles Takes two alleles to be expressed Dominant Allele Only takes one allele to be expressed Codominant Alleles Both alleles contribute to physical expression Blood Type Genes Multiple genes used to determine blood type - called polygenic Polygenic Traits Traits that vary such as height, hair color, or skin color use more than two genes to determine. Rh Blood Group Rh stands for “rhesus monkey” Rh Blood Group Rh Cross + - + ++ +- - +- -- Dominant: Rh+ Recessive: Rh- ABO Blood Group ABO alleles produce specific antigens Antigens: trigger an immune response ABO Blood Group Possible Genotypes Blood Type Genotype A AA AO B BB BO ABO Blood Group Possible Genotypes Blood Type AB Genotype AB O OO Blood Group Genes Both ABO and Rh groups are mentioned at the same time Ex. AB- means AB blood type and Rh- Blood Group Problem 1 Could a man with type B blood and a woman with type AB produce a child with type O blood? Not possible The children of a man with type B blood and a woman with type AB blood could be type A, type B, and type AB, but not type O. Blood Group Problem 2 What if the mother is type O+ and the father is A-? What would the offspring's blood type be? A+, A-, O+, or O- Blood Group Problem 3 If the mother of a child is blood type O+ and the child is A-, what blood type would the father be? Does the Rh factor of the child being - mean that one of the parents has to be negative? The father could be type A or type AB. The father must be the source of the A allele of the child. The father of the child could be either Rh+ (heterozygous with one Rh+ allele and one Rh- allele) or Rh(homozygous with two recessive Rhalleles).