ABO blood group codominance is exemplified by which statement?

ABO blood group codominance is exemplified by which statement?

• A. Monogenic recessive
• B. Polygenic
• C. Codominant inheritance
• D. Environmental influence

Answer: (C)

Codominance at a single gene locus is shown by ABO blood groups because the IA and IB alleles are both expressed when they are together. When someone has IAIB, their red blood cells display both A and B antigens, so neither allele dominates the other and both contribute to the phenotype. This differs from a monogenic recessive pattern, where a recessive trait only appears when two recessive alleles are present, and from polygenic inheritance, which involves many genes influencing a trait. Environmental influence is not part of how ABO blood types are determined. So the statement that best fits is codominant inheritance.

Codominance at a single gene locus is shown by ABO blood groups because the IA and IB alleles are both expressed when they are together. When someone has IAIB, their red blood cells display both A and B antigens, so neither allele dominates the other and both contribute to the phenotype. This differs from a monogenic recessive pattern, where a recessive trait only appears when two recessive alleles are present, and from polygenic inheritance, which involves many genes influencing a trait. Environmental influence is not part of how ABO blood types are determined. So the statement that best fits is codominant inheritance.