A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?



The information is not sufficient to conclude which is the dominant and recessive trait.

  • The genotype and the genotypic ratio is required to determine if the emergent trait is dominant or recessive.
  • The genotypes using which blood group is denoted are as follows:

But according to blood heredity, the Blood type A allele is always dominant and the allele for Blood type O is always recessive .

  • From the chart, blood group A can be denoted as I A I A or I A l where I A is the dominant trait and i is the recessive trait.
  • Blood group O is denoted by ii (recessive allele).

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CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo