Solutions to Genetics Practice Problems

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since 5 Feb 2008

1. If the parents have blood types AB and O, what blood types can their children have?
   The Ab parent has genotype I^AI^B, the O parent genotype ii. Hence, possible offspring are I^Ai = A and I^Bi = B

2. A mother has blood type O, and her child has blood type O. What are the possible blood types of her father?
   The genotype of the mother and her child are both ii. Hence, the father must contribute an i allele, and hence could be I^Ai = type A, I^Bi = type B, or ii = type O

3. If the father is AB negative and the mother O positive, what are the possible blood types for their children?
   If the father is negative, his genotype is --, while the mother could be -+ or ++. Hence, the possible blood types are A+, A-, B+, and B-.

4. An AB negative blood strain is found at a crime screen. John Smith is a possible suspect, but is still at large. If John's father has type O positive blood, could the blood stain have come from John?
   An AB negative blood type implies a genotype of I^AI^B--. Since John's father is O positive, his possible genotypes are ii++ and ii+-. Hence, John could have negative blood, but he would be either A, B, or O, but never AB/