A couple has blood group A and B, respectively. The blood group of their son is AB and the daughter has blood group O.The parents and the children have four different genotypes for the same trait because the:
Correct answer: A. Blood type is controlled by multiple alleles
- A. Blood type is controlled by multiple alleles
- B. Blood type is produced by the cumulative effect of many genes
- C. Alleles of blood group are not expressed as dominant or recessive
- D. Inheritance of blood group follows the laws of Mendelian genetics
Explanation
The correct answer is that blood type is controlled by multiple alleles. The ABO blood group system is determined by three alleles: A, B, and O. Each parent contributes one allele to their offspring, resulting in the possible combinations of AA, AO, BB, BO, AB, and OO. In this scenario, the parents' genotypes are likely AO (blood group A) and BO (blood group B), allowing for children with blood types AB (genotype AB) and O (genotype OO), demonstrating four different genotypes among the family.Option B is incorrect because the ABO blood type is not the result of many genes; it is determined by a single gene with multiple alleles. Option C is incorrect because, while A and B alleles are codominant, the O allele is recessive. Option D is misleading because, although the basic principles of Mendelian inheritance apply, the multiple allele system introduces complexity beyond simple dominance and recessiveness.
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About Mendel's Laws of Inheritance
Mendelian inheritance explains how alleles separate into gametes and assort during reproduction, producing predictable genotype and phenotype ratios. Questions cover dominance, recessiveness, homozygous and heterozygous conditions, the laws of segregation and independent assortment, monohybrid and dihybrid crosses, test crosses and the limits caused by linked genes.
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