Science & Technology2011
A married couple adopted a male child. A few years later, twin boys were born to them. The blood group of the couple is AB positive and O negative. The blood group of the three sons is A positive, B positive, and O positive. The blood group of the adopted son is
Explanation
In blood group inheritance, the ABO system classifies blood types based on the presence of antigens on the surface of red blood cells. The parents with blood groups AB and O can produce offspring with blood groups A (from A antigen and O allele), B (from B antigen and O allele), and O (from O allele inherited from both parents). Individuals with blood group O do not possess A or B antigens and can only pass on O alleles. Therefore, the adopted son, being O positive, aligns genetically with the possibilities from the biological parents’ genotypes. This scenario illustrates Mendelian inheritance patterns and is relevant for understanding genetics in human biology as outlined in UPSC syllabus materials.