There are 4 main blood types: A, B, AB and O. The blood you have depends on the antigen present on the red blood cells and the antibody present. plasma; we'll talk about it later. Blood type is hereditary and which one you have depends on your parents. If both parents have blood type A, the child will likely also have blood type A. Likewise, parents with type B and type B will produce offspring with type B blood. However, if one parent is type A and the other type B, the child will be type AB. Okay, this is all pretty simple, but things get trickier when we introduce blood type O. Blood types A and B are dominant genes, or "alleles" to be more precise. While the allele responsible for blood group O is recessive. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get Original Essay This means that if one parent has blood type O and the other parent has blood type A or B, then the child is most likely to have blood type A or B. For a person to have an O blood type, both of his parents must also have an O blood type. Which makes O blood types extremely rare because the O blood type is recessive unlike its A and B counterparts. Now let's get back to what I was talking about earlier, for example: a blood group will have A antigens on the blood cells and B antibodies in the plasma, the same goes with blood group B. However; AB blood groups will have neither A nor B antigens on the red blood cells and both A and B antibodies are found in the plasma. Finally, blood type O has neither A nor B antigens on red blood cells, but both A and B antibodies are present in plasma. So so far we have four blood groups, A, B, AB and O. However, there are actually eight blood groups, at least in the ABO system. They are A+, A-, B+, B-, AB+, AB-, O+ and O-. So where do the positives and negatives come from. It comes from a third type of antigen, called Rh factor. Your blood cells either have the Rh factor antigens or not. If the Rh factor antigens are present, then you have a positive blood type, if they are not present, you have a negative blood type. Rh negative blood can be given to patients with either Rh negative or Rh positive blood type, providing their primary A, B, or O blood type matches, as previously mentioned. However, Rh positive blood will only be accepted by someone who also has Rh positive blood..