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?

Understanding the inheritance of blood groups involves the principles of genetics, particularly the concepts of dominant and recessive alleles. Blood groups are determined by specific alleles, and their inheritance follows Mendelian genetics.

The ABO blood group system is determined by three alleles: A, B, and O. Alleles A and B are dominant, and O is recessive. This means that the presence of A or B alleles will express the respective blood group, while blood group O is expressed only when both alleles are O.

In the given scenario, a man with blood group A marries a woman with blood group O, and they have a daughter with blood group O. This information provides a basis for understanding the family’s genotypes.

The man’s blood group A can be either AA (homozygous) or AO (heterozygous). The woman’s blood group O is OO (homozygous recessive). Since the daughter has blood group O, it indicates that she inherited an O allele from each parent.

The daughter’s blood group O (OO) confirms that she received an O allele from her mother. The father must have the AO genotype since he contributed the other O allele. This scenario does not explicitly reveal whether A or O is dominant; it only shows that O is recessive.

While this family scenario indicates that the O allele is recessive, it does not provide conclusive evidence about the dominance of the A allele over the O allele. The inheritance pattern only reveals that the father carries the O allele and that the O allele is recessive, as the A trait is not expressed in the daughter.

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