BACKGROUND
This lesson involves human blood types. Although
types O, A, B, and AB were first identified around
1900, anthropologists theorize that type O has
existed since the advent of Cro-Magnon man
approximately 40,000years ago. Type A evolved from
type O through a mutation in the red blood cells
approximately 20,000 years ago. Type A red blood
cells have an additional sugar molecule on the
surface. A similar mutation caused the appearance of
type B approximately 14,000 years ago. Type AB
first appeared around 2,500 years ago. People with
blood type AB have some red blood cells that include
the A sugar molecule and some that have the
B sugar molecule. The Rh factor, a protein found on
the surface of some red blood cells, was discovered
in 1940. Type O negative is called
the universal donor because a transfusion introduces
no additional A or B sugars or Rh protein
into the recipient's bloodstream. Agglutination, or
clumping, occurs when red blood cells of A, B, AB,
or Rh positive blood are added to the bloodstream
of a person whose red blood cells lack the protein
or sugar. Researchers are seeking
ways to remove the sugars and proteins from types
A, B, AB, and O positive red blood cells to produce
greater quantities of the universal donor.
A compatible blood type is one that introduces no
new elements into the recipient's bloodstream. The
compatible families, or all blood types that can safely
donate blood to a given blood type, can be determined
by examining the Venn diagram shown in figure 1. The
universe for the diagram is O negative,
since all blood is either O negative or O negative with
added sugars or proteins. The three overlapping
circles represent blood types with the A sugar, the
B sugar, and the Rh protein. The diagram has eight
regions, one for each blood type. Using figure 1 and
the definition of compatible blood types, you should
determine all compatible blood types for each of the
eight types and shade them in the diagrams below (B+
has been shaded for you in figure 2).
figure 1
For example, my blood type is B+ (the same
as my philosophy of life!). The compatible blood types for
B+ are: B+, B-, O+,
and O- because no new elements are introduced into
the bloodstream.
Figure 2 shows the compatible blood types for B+. You should fill
in the other seven diagrams showing compatible blood types for A+, A-, B-, AB+, AB-,
O+, and O-.
Fig. 2 (Blood Types compatible with B+)
Blood Types compatible with B-
Blood Types compatible with O-
Blood Types compatible with O+
Blood Types compatible with A-
Blood Types compatible with A+
Blood Types compatible with AB-
Blood Types compatible with AB+
The following table shows the approximate blood-type percents for
people living in the United States:
| Blood Type | Percent |
|---|---|
| O+ | 38% |
| O- | 8% |
| A+ | 32% |
| A- | 7% |
| B+ | 9% |
| B- | 2% |
| AB+ | 3% |
| AB- | 1% |
Now use the approximate blood-type percents, given in the table above, to determine the theoretical probabilities for each blood type. In other words, determine all the compatible blood types for a given type (that is, the blood types that the given type can safely receive). Then sum up the probabilities to determine what percent of the population could donate blood to a person with that type. Remember, you don't want to introduce any new sugars or proteins into that blood type.
Fill in the table below (B+ has been done for you):
| Blood Type | Compatible with ... | Theoretical Probability |
|---|---|---|
| O+ | ||
| O- | ||
| A+ | ||
| A- | ||
| B+ | B+, B-, O+, O- | .09 + .02 + .38 +.08 = .57 |
| B- | ||
| AB+ | ||
| AB- |