Background information:



Title: Blood Types

Target Audience: high school: best for small groups

Show Type: hands on

Supplies: blood type test kit, paper/pen or chalkboard for explanations

Description/How to:

-prerequisites: a basic knowledge of antibodies and simple Mendelian

genetics would be helpful, but could be explained during the demo if

needed.

-objectives:

1) understand the inheritance patterns of ABO and Rh alleles, and how

each genotype produces each phenotype

2) perform a blood type test using SL’s blood typing kit

3) learn major applications of blood typing: transfusions, paternity tests

-abstract:

Explain technical background info, then provide instructions on how to do a blood type, followed by each student typing a “blood” sample from the kit

-step by step instructions for the demo:

Prep work:

1) open the kits and divide up the “blood” samples, test sheets, and solutions for easy access during the show.

2) Pack a plastic tablecloth or plastic plates so the solutions and wet test sheets do not bleed through and stain the tables.

During the demo:

1) Set up table cloth or plastic plates ahead of time. Give a test sheet, sample, and any necessary solutions to each student.

2) Have the audience put 1-2 drops of sample onto each of the 3 test areas (A, B, Rh).

3) After waiting an appropriate amount of time (see kit instructions), have the students check their sheets for clumps, and deduce the blood type of their sample.

[See kit’s user manual for additional details specific to that kit.]

Clean-up:

1) Throw out the used test sheets and plates between groups.

2) At the end of the day, throw out the tablecloth. Pack up the remaining supplies for future demos.

Age Appropriate Explanation:

Background Info:

There are three variations (alleles) of the ABO blood group gene 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 iA and i B alleles are co-dominant, meaning that if both alleles are present then both blood proteins will be expressed in the form of the A or B surface protein (i.e. neither allele will mask the effects of the other… contrast with the complete dominance of Rh factor inheritance) but both are dominant over the i allele. If neither the iA nor the iB allele is present, then the person must have 2 i alleles, which do not code for either protein, resulting in an “O” blood type.

Here are the 6 ABO genotypes and the resulting 4 phenotypes:

• iAiA or iAi - produce the A protein (type A).

• iBiB or iBi - produce the B protein (type B).

• iAiB - produces both the A and B protein (type AB).

• ii - produces neither protein (type O).

Question for the audience: If one parent is “O” then they cannot possibly have an AB baby even if the other parent is AB. Why? Answer: each parent passes down one and only one allele, so the AB parent could only pass down iA or iB , and the O parent has only the i allele to give.

The Rh factor (Rh is for Rhesus monkey, where it was first identified) is either present (+) or absent (-). Rh+ is completely dominant over Rh-, so a Rh+/Rh+ individual has the same phenotype as a Rh+/Rh- person. Blood types are described as the ABO blood type followed by the presence or absence of the Rh factor (e.g. O+ , AB-).

Significance:

Blood typing is important for blood transfusions to see if the donor and recipient blood may be compatible (note: there are many other factors which also affect compatibility). O- blood is considered to be the universal donor since is expresses none of the 3 blood proteins (A, B, Rh) so it will not elicit an immune response by antibodies against any of those 3 proteins. AB+ blood is the universal recipient because it already has all 3 blood proteins so the body will not perceive any of them to be foreign and thus will not attack them with antibodies.

If an incompatible transfusion is performed (i.e. giving A+ blood to a B+ recipient), then the results can be deadly. As seen in the blood typing demo, blood cells aggregate (clump together) when attacked by antibodies. However, when the antigen (blood protein in this case) is not present, then the antibodies have nothing to bind to, so the blood cells are unaffected in a compatible transfusion (e.g. giving B- blood to an AB- recipient).

Blood typing used to be the primary method of paternity testing, but now it has largely been replaced by DNA tests since they are more specific and definitive. Example (if time permits): a baby has AB+ blood, and the mother has type A- blood. The 3 possible fathers have types A+, AB-, and B+. Which one(s) could be the father? Answer: only the last man (B+) since both the Rh and B proteins must have come from the father.

Safety: explain the importance of blood safety to the kids (disease transmission) even though the kit does not contain real blood. Do not sniff or taste any of the solutions, and take care not to spill them in anyone’s eyes.

Technical Background information for SL members:

The Rh factor: In reality, there are 3 loci (C, D, E) which determine the Rhesus phenotype. If an individual's Rh genotype contains at least one of the C, D, E antigens, then they are Rh+. Only individuals with the genotype cde/cde are Rh-.

The importance of the Rh factor is largely found in Rh- mothers carrying an Rh+ baby. The mother makes antibodies to the Rh factor since some of the baby’s red blood cells enter the mother’s blood stream. These will not take effect fast enough to harm the baby, but they can cross the placenta to attack a second Rh+ fetus in a later pregnancy.

Blood typing can only be used to rule out paternity or suggest paternity but it cannot prove paternity. DNA fingerprinting at 7 loci however can suggest paternity with such a high probability that the odds (< 1 in 10 billion) are that no one else could be the father since there are only 7 billion people in the world.

For further information on blood types, see:



For further information on other (non-ABO) blood proteins, see:



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