Question

Blood type is a codominant trait. Determine the offspring for the following cross. Include genotype, phenotype, and ratios.

IAIB x IAIO
a) Genotype: IAIA, Phenotype: Type A
b) Genotype: IAIB, Phenotype: Type AB
c) Genotype: IAIO, Phenotype: Type A
d) Genotype: IOIO, Phenotype: Type O

Answer 1

The cross between an individual with IAIB genotype (Type AB blood) and IAi genotype (Type A blood) yields genotypes IAIA, IAIB, IAi, and IBi, corresponding to phenotypes Type A, Type AB, Type A, and Type B blood respectively, with a phenotype ratio of 2 Type A: 1 Type AB: 1 Type B.

Step-by-step explanation:

The genotype and phenotype ratios for the offspring of a cross between an individual with IAIB genotype (type AB blood) and an individual with IAi genotype (type A blood) can be determined by creating a Punnett square.

The predicted ratio for the genotypes is 1 IAIA: 1 IAIB: 1 IAi: 1 IBi, which corresponds to a phenotype ratio of 2 Type A: 1 Type AB: 1 Type B. There is no offspring with the genotype ii, hence no Type O blood phenotype in this cross.

In codominance, both alleles in a heterozygous individual are fully expressed, leading to a mixture of characteristics rather than an intermediate form. An example is the AB blood type, where both A and B antigens are present and expressed. Conversely, the i allele is recessive and does not produce any antigen, resulting in Type O blood when homozygous (ii).