A, contains antigen A (a
chemical found on the
surface of the blood cell)
B, contains antigen B
AB, contains antigen A, and
O, does not contain an
Type O- is the universal
Type AB+ is the universal
Genetics of Blood Type
There are three forms of the gene (alleles) that
control the ABO blood group, which are
designated as iA, i B, and i. You have two
alleles (one from your mother and one from
your father), which are referred to as your
genotype. The inheritance of the alleles is co-
dominant, meaning that if the allele is present,
it gets expressed. (See How Gene Pools Work
for more information.) The following genotypes
will yield these blood types:
iAiA or iAi - Both genotypes produce the A
protein (type A).
iBiB or iBi - Both genotypes produce the B
protein (type B).
iAiB - This genotype produces the A and B
protein (type AB).
ii - This genotype produces no protein (type O).
So, your blood type does not necessarily tell you
exactly which alleles you have. For example, a
person with blood type A could have either two iA
alleles or one iA allele and one i allele. It is
possible for two parents with the same blood type
(A or B) to have a child with type O blood. Both
parents would have to have a mixed genotype,
such as one i allele together with either one iA or
one iB allele.
Who has your blood?
This is a chart
Caucasians in the U.S.
and their blood type.
U.S. Blood-type Distribution
38 percent of population
34 percent of population
Info from Red Cross.
9 percent of population
7 percent of population
6 percent of population
3 percent of population
2 percent of population
1 percent of population
rH Factor (+ or -)
rH factor is a protein
that covers RBCs
If you have the rH you
If you do not then you are
rH comes from the
Type O- donors are known as
because their red blood cells
may be transfused to patients
of any other blood type in an
emergency situation or if the
needed blood type is
Because any patient can
receive O negative red blood
cells, there is a need for O
donors to give more often and
shortages of type O blood are
Type AB plasma can be given
to anyone as well.
But whatever your blood type,
your blood is important to
Wrong blood could equal
to blood clots
History of Blood Typing
Prior to 1939 the only significant blood group antigens recognized were A, B and O.
Transfusion medication was thus based on the matching of ABO groups. In spite of
ABO matching, blood transfusion continued to result in unexplained morbidity
(sickness) and mortality (death).
As the 1930s ended, two significant discoveries were made that would further the
safety of blood transfusion. These discoveries eventually would result in defining the
most extensive blood group system known. That blood system is commonly called “Rh”
after the rhesus monkey. Technically, however, it is known as D. A person with the D
factor in their blood is Rh positive.
In 1930, two doctors named Levin and Stetson reported on a woman who had
experienced a blood transfusion after a stillbirth delivery. She had received blood from
her husband. By 1939 standards, their blood should have been compatible. However,
after the transfusion the woman became sick and her baby died from Erythroblastosis
Fetalis. The doctors did further testing on the parent’s blood and found that for some
reason their blood reacted differently.
Around the same time two other scientists, Landsteiner and Wiener reported on an
antibody made by guinea pigs and rabbits when injected with rhesus monkey red blood
cells. They then conducted similar experiments with human blood. The blood seemed
to have a factor that caused 85 percent of the human red blood cells to clump together.
These scientists decided to call the factor D but it became known as Rh.
What happens in a pregnancy when the baby’s blood is different than the mother’s blood?
Finally, the Rh factor is important for pregnant women. If an Rh+ man and an Rh-
woman have a child, the child can be Rh+ or Rh-, depending upon the genotype of the
father. If the baby is Rh+, this can cause problems. While in the womb, some blood
cells from the baby will cross the placenta into the mother's blood stream. The mother
will make antibodies to the Rh+ cells. If the woman becomes pregnant again and if the
baby is Rh+, the mother's anti-Rh antibodies will cross into the baby's blood and
destroy its red blood cells, which can kill the baby. If diagnosed early, it is possible to
save a baby under these circumstances by replacing the baby's blood with transfusions
that are free of the Rh antibodies. Also, if this situation is known, it is possible to treat a
Rh- woman with anti-Rh antibodies (RhoGam) immediately after childbirth to inactivate
the baby's Rh+ cells and prevent the mother from forming anti-Rh antibodies
During pregnancy the mother’s blood and the baby’s blood co-mingle. When the mother’s
blood is different than the baby’s blood, the mother’s blood becomes sensitive to the
difference. The mother can develop antigens that can attack the baby’s blood cells and
destroy them. This is referred to as isoimmunized.
If the mother’s blood and the baby’s blood are the same Rh, then there is no problem.
The first time a woman is pregnant, and if the baby has a different Rh, the mother will develop
just a few antigens. However, if she has successive pregnancies with a baby who has a
different Rh factor, she will develop more and more of these attack antigen cells.
A drug called Rhogam helps treat this problem.
Exploration #2: (40-50 minutes)
Before Class: Get three 500 milliliter beakers and fill each to the 500
mL mark (about 2.25 cups). Into one beaker, add 5 drops of yellow
liquid food coloring. Into a different beaker add 5 drops blue food
coloring. Into the third beaker add 10 drops green food coloring. Then
distribute smaller beakers of each color and one of plain water to each
lab station (or if the students are to work at their own desks, put them
on trays including beakers.) Also include a testing plate (or small clear
beakers or just a plastic overhead sheet) for each group and four
(Lab Notes: When preparing the food coloring solutions be conscience
about how well the green food coloring masks the blue and yellow
colors. Because different manufactures may affect the coloration of the
solutions, it is recommended that the teacher run the experiment
beforehand to confirm that the solutions will work as desired. Also, you
may also find that students are able to identify the colors of the
solutions better if a white piece of paper is kept under the testing vessel
Explain to students that when people donate blood to each other sometimes the blood from
one person clumps (the small particles in blood bind together into larger masses much like
yesterday’s mixture) with the other and causes a blockage but that other people can
donate blood to other and it will not clump. Today they will simulate which blood types a
person who is injured can get from others and which kinds will cause clumps.
Hand out the student worksheet at the end of the lesson.
Instruct students that we will use food coloring to represent the four basic blood types of
people: A B AB O. Write the following information on the board: A-Yellow, B-Blue, AB-
Green, O-Clear water.
According to the worksheet (included at the end of the lesson), students will mix different
colors (blood types) and indicate if each mixture stays the same color-a successful
donation, or if the mixture changes color-an unsuccessful (clumping) donation. Instruct
students to use one dropper for each color and that they only need to use a couple of
drops each time. Provide any other basic instructions for groups to get started and monitor
It is recommended that the teacher walk the students through the first two tests so that
students are clear on how to complete the worksheet.
While students are working, copy table from the student worksheet on board or onto an
Once the groups have tested their samples, have the students clean up their supplies.
After students have returned to their seats, go through the worksheet and have students
tell you if there were reactions or not between what blood types. Collect the worksheets.
Explanation: (30-40 minutes)
Describe how blood is used to donating to other persons.
During this discussion, make sure to incorporate these topics:
What are the four blood types of people?
What does blood do?
How does it do it? Make sure you talk about the small molecules in the blood that
carry oxygen to the body cells (Hemoglobin, myoglobin), clotting particles,
dissolved substances in the blood like sugars, etc.
Why is blood important to the body?
What would happen to the body if blood weren’t there? What causes us to loose
Talk about how by being able to donate blood to others, we are able to prevent
persons from dying at times when other organisms would die.
Talk about how people have other factors that influence whether one person can
donate to another such as Rh.
For homework, have students try to find out what blood type they are
and what blood types their family members are. Inform them that
their parents may know this information or it should be included on
their birth certificate.
Elaboration: (30-40 minutes)
Before class make enough copies of the blood type cards and cut apart. (Please note: the
card pages below include some cards with both ABO and Rh and others with just ABO.
This allows you the flexibility to introduce the additional Rh factor if time allows. Otherwise,
only the ABO cards would be necessary.)
Ask students that know their blood type to raise their hands. Give these students their
blood type card. For students who do not know their blood type, randomly distribute other
cards to students.
Instruct students to put their name at the top of their cards. They should then circulate
around the room and determine what students in the room they would be able to donate to
and receive blood from. Tell students how long they have to find at least 2 persons for
each blood type groups.
Once that time has arrived, have the students take their seats. Choose students from each
blood type and randomly put their names on the board (or overhead). Have students tell
you who that student can donate to and who they can receive from. Use arrows to show
Ask the students to discuss how donating and receiving blood by O (or O-) blood types are
different from that experienced by AB (or AB+) blood types. This could be done in science
Collect the students’ cards and notebooks for grading.