Blood - audio from class lecture
Co-dominant alleles: Human ABO blood type
There are 2 dominant alleles (A and B) and one recessive (O).
A and B alleles determine sugars present on cell membrane of red blood cells.
If you have A, then you produce type A sugars.
If you have B, then you produce type B sugars.
If you have O, then you produce no sugars.
|
Possible Genotypes Phenotypes |
||
| AA | TYPE | A |
| AO | TYPE | A |
| BB | TYPE | B |
| BO | TYPE | B |
| AB | TYPE | AB |
| OO | TYPE | O |
When you need a blood transfusion, they try to match blood types.
If you give type A blood to someone without type A blood, they have no type A
blood sugars on their own red blood cells so their immune system will attack the
transfused blood because it recognizes that it is foreign.
While they try to give type A blood to a person with blood type A, type O could
also be used. Because there are no blood sugars in type O blood that the type A
person’s body hasn’t seen. Therefore, type O is called the universal donor and
type AB is the universal recipient.
What about positive and negative?
That’s a different gene.
The Rh factor is another sugar on red blood cells.
It’s called Rh for Rhesus, as it was first found in a Rhesus monkey.
You are Rh positive if you have the blood sugar, but Rh negative if you do not.
Thus the ultimate donor is?
O negative
Ultimate recipient?
AB positive
What are the relative frequencies of these blood types in humans?
| O | Positive | 37% |
| O | Negative | 6% |
| A | Positive | 34% |
| A | Negative | 6% |
| B | Positive | 10% |
| B | Negative | 2% |
| AB | Positive | 4% |
| AB | Negative | 1% |