Task

In humans the ABO blood groups are determined by three alleles of one gene (I⁰, Iᴬ, Iᴮ) and the Rh factor by an autosomal dominant gene (R — Rh-positive, r — Rh-negative); the genes are on different chromosomes. An Rh-positive woman of group II (A) had a father of group I (O) who was Rh-negative. She married an Rh-negative man of group III (B) whose mother was group I (O). 1) Explain multiple allelism and codominance using the ABO system; write the genotypes of each blood group. 2) Determine the spouses’ genotypes with reasons, write the cross and gametes; is there a risk of Rh incompatibility in this family — explain. 3) Calculate the probability (%) of each blood group and of Rh-negativity among the children. 4) Calculate the probability (%) of a group I (O), Rh-negative child. 5) Calculate the probability (%) that two successive children are both group IV (AB) and Rh-positive. For each part, write out the law or method used (cross scheme, formulas, reasoning) and all calculations step by step.