1. ABO Blood Type: An Example of Genetic Variation
Humans have two copies of an enzyme that makes carbohydrates that stick off of the red blood cell plasma membrane.
In some humans this enzyme has a structure that causes it to make A type carbohydrates.

2. ABO Blood Type: An Example of Genetic Variation
In others this enzyme has a structure that causes it to make B type carbohydrates.
In others they may have copies of both enzyme structures.
In still others this enzyme has a structure that makes in nonfunctional so no carbohydrate is made.

3. How can one enzyme have so many different possible structures?
Let’s look at how these protein enzymes are made: from DNA to mRNA to Protein…

4. The Flow of Genetic Information from DNA to RNA to Protein
DNA functions as the inherited directions for a cell or organism.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

5. From Nucleotides to Amino Acids: An Overview
Genetic information in DNA is transcribed into RNA and then translated into polypeptides (proteins).

6. The Genetic Code

7. How does a change in the DNA code affect the structure of a protein?

8. ABO Blood Type: An Example of Genetic Variation
So the ABO gene has
different DNA sequences that code for the
different protein enzyme structures that makes one of these
different types of carbohydrates.
Genetic Variation!!!

9. The immune system produces antibodies!
These may cause clotting when blood cells of a different type enter the body.