What are the possible genotypes?
What are the ABO blood types?
There are four main blood types (the phenotype), although there are six possible genotypes: A, B, AB, and O. They’re determined by whether or not there are A or B antigens on the red blood cells and in the plasma. Antigens are asubstances that are foreign or unknown to the body that causes an immune response. If you have type A blood, you have A antigens on the blood and B antigens in the plasma. That’s the opposite for type B blood, which means that you have B antigens on the blood, and A antigens in the plasma. For those with type AB blood, they have both A and B antigens on the blood, but neither in the plasma. Like type B, that’s the opposite situation for type O blood people. Those with type O blood have no antigens on the blood, but both A and B in the plasma. Along with A and B antigens, there’s another antigen called the Rh factor. If the Rh factor antigen is present on the red blood cells, the blood type is considered positive (+). If it is absent, it’s considered negative (-).
The six possible blood genotypes are: AA, AO, BB, BO, AB, and OO. Since each parent will give one allele for each trait, and blood is a codominant trait, it’s possible for the child to have a mixed blood type. The alleles for A and B type blood are dominant, and O is recessive. It’s for those reasons that AO and AA will always be type A blood. O is recessive, so if someone has AO blood, they basically have type A blood. The antigens will always be A on the blood and B in the plasma. To have type A blood, one parent must give the allele for A blood and the other must either give the allele for A or O blood. Same for B type blood. For AB type blood, one parent has to give the A allele and the other has to give the B allele. For type O blood, both parents have to give the allele for type O blood. The Rh factor is either given or not; it only affects whether or not the blood is positive or negative.
Each type can only give and receive from certain types of blood because of the antigens they contain in the plasma. For example, with type A, it contains the A antigen on the blood and the B antigen in the plasma. It’s for that reason that type A can only give to A and AB blood, and can only receive from A and O blood. The antigen in the plasma is used to make antibodies, which in this case makes antibodies for the B antigen. With all those antibodies for the B antigen, the bodies of people with type A blood will reject any type of blood with the B antigen on the blood cells. It’s vice-versa for type B blood. Since the locations of each antigen is reversed, the reactions are also reversed. The body will make antibodies against the A antigen, but will allow the B antigen.
The special cases, AB and O, have different immune responses for blood transfusions. Type AB blood will accept any type of blood, since both antigens are located on the blood cell and not in the plasma. It’s the opposite for type O, which has both antigens in the plasma. Since the body will make antibodies for both A and B antigens, those of type O blood can only receive blood from others with type O, but can give to all types because there are no antigens on the red blood cells.
In addition to those rules, if the blood has the Rh factor, it can receive blood from compatible types, with or without the Rh factor. However, if the blood doesn’t have the Rh factor, it can only receive from compatible types, without the Rh factor.
In short, if a type of blood has a certain antigen in its plasma, it can’t receive blood that has that antigen in its red blood cells. If that type of blood is positive, it can receive from both negative and positive types of blood, as long as the donor doesn’t have the antigen in their red blood cells that the recipient has in their plasma. If the recipient’s blood type is negative, it can only receive blood from donors that also have a negative blood type that is compatible with the recipient’s blood type.
The presence of those 3 antigens (A, B, Rh factor) all affect how blood can be transferred. Type A+ blood can only give blood to positive A and AB, and can only receive blood from A and O. Type B+ blood can only give to B+ and AB+, and can receive blood from B and O. Type AB+ can only give to type AB+, but can receive blood from every type. Type O+ blood can give blood to any positive blood type, and but can only receive blood from type O. Type A- blood can give blood to both kinds of A and AB blood, and can only receive from negative A and O blood. Blood B- can give to both types of B and AB blood, but can only receive from B- and O-. Type AB- can give blood to AB, and can receive from negative AB, A, B, and O. O- can give blood to every type, but can only receive from others with O- blood.
Why can't some types of blood accept others?
Which donors are compatible with each recipient?
Get to know the ABO Blood Types!
There are 4 questions on this page, which can and will be answered on the paragraph right below it! Along with the paragraphs are several images which will help you understand the content more efficiently.
References
Blood Types. (n.d.). American Red Cross. Retrieved April 10, 2014, from http://www.redcrossblood.org/learn-about-blood/blood-types
Desimd. (n.d.). Desimd. Retrieved April 10, 2014, from http://www.desimd.com/sites/default/files/Blood%20group%20medical%20symbol.jpg
What Are Blood Group Antigens All About?. (n.d.). - For Dummies. Retrieved April 10, 2014, from http://www.dummies.com/how-to/content/what-are-blood-group-antigens-all-about.html
Wikimedia. (n.d.). Wikimedia. Retrieved April 10, 2014, from http://upload.wikimedia.org/wikipedia/commons/thumb/3/32/ABO_blood_type.svg/824px-ABO_blood_type.svg.png
Blood Types. (n.d.). YouTube. Retrieved April 28, 2014, from http://youtu.be/KXTF7WehgM8
The Blood Typing Game. (n.d.). The Blood Typing Game. Retrieved April 28, 2014, from http://www.nobelprize.org/educational/medicine
