How many genotypes are in the ABO+/- system?

There are six genotypes in the ABO blood group system and three genotypes in the Rh +/- system.

Explanation: The ABO system is a system of blood group based on the type of antigens present in the red blood cells. There are basically four types of blood groups: A, B, AB and O. Blood group A has A antigen, blood group B has B antigen, blood group AB has A and B antigens while blood group O has neither A nor B antigen.

The possible genotypes for these blood groups are AA, AO, BB, BO, AB and OO. Blood group A has two possible genotypes: AA and AO. Blood group B has two possible genotypes: BB and BO.

Blood groups ==> Genotypes

A ==> AA, AO

B ==> BB, BO

AB ==> AB

O ==> OO

The Rh+/- system is the second most important blood system after the ABO system. Rhesus factor was first discovered in rhesus monkey. Rhesus factor inheritance is independent from the ABO blood groups. An individual can either be Rh + or - based on the presence of rhesus antigen in the red blood cells.

Genotypes for the Rh factor are +/+, +/-, and -/-. Individuals who are rhesus positive will have either +/+ or +/- genotype while individuals who are rhesus negative will have a genotype of -/-.

Rhesus factor ==> Genotypes

Positive ==> +/+ (homozygous),

or +/- (heterozygous)

Negative. ==> -/-

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