Mendel is known as the father of modern genetics, however there are some genetic characteristics which cannot be described by simple Mendelian genetics. Such is the case with human blood types where there are 3 alleles for same gene, A B, and o. A parent can pass allele A, B, or o to the offspring based upon the parent’s genotype.

From these three alleles, there exist 4 blood types (phenotypes): A, B, AB, and O, and there are six genotypes: AA, Ao, BB, Bo, AB, or oo. This is an example of codominance where both the A and B alleles are co-dominant to each other.

Blood types can be used in the forensics to find if blood is from the victim or criminal. Blood types can be used to find the parental source in situation where the father is unknown; though, blood types can only remove particular blood types. DNA fingerprinting is a better method which is used often in the criminal and the parental determination cases.

Punnett squares like the one shown above are used to find the probabilities (percentages) for the genotypes of offspring given specific genotypes for the parents.

A)  In above example, Punnett Square represents a cross (mating) between the male (on the left side) with the blood type AB, and a female, (top of square), with blood type A, genotype Ao. Explain the possible blood types for the offspring?

a) Specify the possible blood types for the offspring?

b) State the ratios or percentages for each possible blood type from this cross?

c) What blood type is not possible from this cross?

B) Fill out two Punnett squares for a cross between a male with blood type B and a female with blood type AB.  Build two Punnett squares and answer the following questions about them.

a) Explain the possible blood types for cross between type B (BB or Bo?) male and AB female?

b) Explain the percentages (%) or probabilities for each blood type in the offspring?

c) Explain the blood type(s) would not be possible in the cross between these two parents?