GENETICS OF ABO AND Rh BLOOD TYPES

In 1900, Karl Landsteiner discovered and described the ABO blood groups. In 1910, von Dungern and Hirszfeld reported they were genetically inherited. We now know that a person’s ABO blood type depends upon the form(s) of polysaccharide on their red blood cells. The gene specifying an enzyme that synthesizes this polysaccharide has three alleles, which influence the sugar’s form. Two of the alleles (IA and IB) are codominant; when paired in a heterozygote, they both are expressed. The third allele (i) is recessive and can be masked by either of the others.

Landsteiner was also involved in the discovery of the Rh blood groups, which are governed by two alleles. Someone with one or more Rh+ alleles makes a red blood cell protein called Rh factor. Someone with the Rh- allele doesn’t make this factor.

ACTIVITY

In this activity, you will use the tutorial on the University of Arizona’s Biology Project Web site to further investigate the genetics of blood types.

Use your browser to go to http://www.biology.arizona.edu/human_bio/problem_sets/blood_types/Intro.html.

Use what you learn in this tutorial and the information in your text to answer the following questions:

1. How many possible genotypes are there at the ABO locus? How many different phenotypes can be produced?
2. What types of gametes would a person with type O- blood produce?
3. What types of gametes would a person with AB+ blood, who is heterozygous at the Rh locus, produce?
4. Could an AB+ father and an O- mother have an A+ child?
5. Could an A- father and an O- mother have an A+ child?