Question

We are familiar with blood phenotypes A, B, and O and the 3 alleles I^A, I^B and i There is a second locus, H, which allows synthesis of the precursor to the substances on the blood cell surface that make for having A or B phenotype. A recessive mutation, h, at this site, in the homozygous condition, prevents this precursor from forming. In that circumstance, A, B, or AB phenotype cannot be expressed despite their alleles being present; this is called the Bombay phenotype. In the heterozygous condition, h allele does not interfere with expression of blood type. Draw a Punnett Square for the cross between an individual with I^AI^OHh genotype and one with I^AI^Bhh genotype. State the blood phenotypes for these parents. List the phenotypes and their ratios that result from their mating.

Answer 1

Ia_H_ = A

Ia_hh = O

Ib_H_ = B

Ib_hh = O

IaIbH_ = AB

IaIbhh = O

IoIoH_ = O

IoIohh = O

IaIoHh × IaIbhh

Gametes	Iah	Ibh
IaH	IaIaHh (A)	IaIbHh (AB)
Iah	IaIahh (O)	IaIbhh (O)
IoH	IaIoHh (A)	IbIoHh (B)
Ioh	IaIohh (O)	IbIohh (O)

PR - 4 (O) : 2 (A) : 1 (B) : 1 (AB)

GR - 1:1:1:1:1:1:1:1

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