A man has blood group A. His mother had blood group O…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A man has blood group A. His mother had blood group O. He marries a woman of blood group B whose father had blood group O. They plan to have children.
- What is the genotype of the man, and what is the genotype of the woman?
- What is the chance that a child has blood group O?
- What is the chance that a child has blood group AB?
- What is the chance that a child has group A or group B?
Need a reminder? The key ideaShow
In incomplete dominance the heterozygote is intermediate, and the F2 ratio is 1 : 2 : 1 for the phenotype too. The ABO gene has the alleles , and i. and are codominant, and both are dominant over i. In polygenic inheritance each dominant allele adds one unit, and the classes follow the binomial numbers.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. The man has group A, and his mother is ii. The woman has group B, and her father is ii.
Plan. Find the hidden allele of each parent. Then use the Punnett square.
Step 1. (a) The man got an i from his mother, so he is . The woman got an i from her father, so she is .
Step 2. The square. The man gives or i. The woman gives or i. The boxes are (AB), (A), (B) and ii (O), one box each.
Step 3. (b) Group O is one box in four: .
Step 4. (c) Group AB is one box in four: .
Step 5. (d) Group A and group B are one box each: .
Answer: (a) and ; (b) ; (c) ; (d) .
Check. All four groups are possible, and the four chances add up to .
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