Blood Type (Michael Kim)

Title: Inheritance of Blood Type

Principle(s) Investigated: Students will investigate the effects of inheritance in blood type.

Standards:

HS-LS3-3

Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population. [Clarification Statement: Emphasis is on the use of mathematics to describe the probability of traits as it relates to genetic and environmental factors in the expression of traits.] [Assessment Boundary: Assessment does not include Hardy-Weinberg calculations.]

HS-ETS1-2

Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.

Materials:

Blood samples from Mrs. Johnson, Mrs. Johnson, Mr. Wilson, child 1, child 2, and child 3

Samples of blood type A, B, AB, and O

Anti-A and B serum

Toothpicks (12 per group)

Student handout

Procedure: To test a person's bloodtype, you can mix a sample of blood with antibody A or B:

1. Add two drops of a blood sample to one well and two drops to another well.

2. Add two drops of the appropriate antibodies to each of the sample wells.

3. Stir each sample to check if agglutination occurs (clotting/thickening of the sample).

If the blood cells have the appropriate antigens on their surface, agglutination occurs. For example, if anti-A serum is added to a sample of blood and agglutination occurs, that means the blood contains cells that have type A antigens on their surface. Note that blood type AB has both A and B antigens on their cell surfaces while blood type O has neither antigens on their surfaces.

Record your data in this spreadsheet

Student prior knowledge: Students should know blood types and their red blood cell surface antigens and be able to determine which antibodies are present in their respective blood plasma.

Explanation: The purpose of this lab is to give students an opportunity to apply what they know about the inheritance of traits to solve a problem. This lab also gives students an opportunity to use an explanatory model, in this case the multiple allele model of inheritance, as a way to make sense of a natural phenomenon. Students will also learn about the differences between observations and inferences and between data and evidence in science.

Questions & Answers:

1. A person with blood type-A would typically not produce anti-A antibodies. Why is this a benefit to the person?

If anti-A antibodies were produced, the person's red blood cells would agglutinate and the person would quickly die.

2. People with type-AB blood, which is the rarest, are often referred to as universal recipients. Explain why people with type AB-blood can receive any blood type.

People with blood type-AB blood have both A and B antigens on the surface of their blood cells, so both are recognized as as self, meaning that blood type-AB lacks antibodies of either kind. Therefore, a person with blood type-AB can receive other types of blood with no reaction. Blood type-A would have antigen A proteins on their blood cells, invoking no response. Blood type-B would have antigen B proteins on their blood cells, invoking no response, and blood type-O has no antigens, thus provoking no response.

3. Explain why people with blood type-O are considered universal donors, but can only receive blood from other type-O donors.

People with blood type-O have neither A nor B antigens on their cells, but have both anti-A and B antibodies in the bloodstream. Therefore, type-O's can donate their blood to any recipient because type-O blood cells won't be recognized as a foreign body due to the lack of antigen proteins. However the person with blood type-O can only receive blood from other type-O's because their antibodies would recognize blood cells from A, B, and AB donors and agglutinate.

Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.

This concept of blood typing is used in the medical field in order to determine whether a recipient can be infused with the correct blood type donor in emergency situations. Although blood type is an inherited trait, the U.S. judicial system does not recognize ABO blood typing as an acceptable way to determine paternity because many individuals can have the same blood type. In the United States, for example, approximately 44% of the population has type-O blood, 42% has type-A blood, 10% has type-B blood, and 4% has type-AB blood. ABO blood-typing, however, can be used to conduct a quick and inexpensive test for ABO blood type to determine if further testing using DNA analysis is warranted. Although beyond the scope of this lab, blood typing is especially important for pregnant women. If the mother is Rh-negative and the father is Rh-positive, the child will likely be Rh-positive. In these cases, the mother needs to receive a drug called RhoGAM. This drug will keep her body from forming antibodies that may attack the baby’s blood cells if their blood becomes mixed, which often happens during pregnancy.

Photographs:

Two drops of blood type-A in each well with two drops of antibodies A and B respectively.

Agglutination on sample with antibody A (clotting), no reaction with antibody B on the right well.

Videos: