A classmate tells you that a person can have type AO blood. Do you agree? Explain.

A blood group refers to the classification of blood based on the presence of the sugars or proteins on the membranes of red blood cells called the antigens and the proteins in the blood plasma called the antibodies. Karl Landsteiner in the year 1901, classified the blood groups into the four groups A, B, AB and O which is called the ABO system of blood grouping.

If a classmate tells that a person can have type AO blood, we cannot agree. There are only four blood groups A, B, AB and O and they can be either negative or positive based on the absence or presence of the Rhesus antigen. A person with blood group A can have the allele (alternative forms of genes) A with the genotype AA or AO. Hence AO is not a blood group and it can be one of the genotype of blood group A.

No, the only blood types possible are A, B, AB, and O. also + or - for each.