<prompt> A 40 year old female patient complains of excessive bleeding. Patient gives a history of road traffic accident 5 hours ago and had a lacerated wound on lower back region. Blood grouping test reveals presence of antigen A and antigen B. This system for blood grouping consists of 3 major allelic genes which are located on:Chromosome 8Chromosome 9Chromosome 10Chromosome 7  <response>: This system consists of 3 major allelic genes; those are A, B and O. They are located on long arm of chromosome 9. These genes control the synthesis of blood group antigens A and B. Based on the presence or absence of antigen A and antigen B, blood is divided into 4 groups i.e A, B, AB and O. 