The Genetics of Blood

Genetics of Blood Types Your blood type is established before you are BORN, by specific GENES inherited from your parents. You inherit one gene from your MOTHER and one from your FATHER. These genes determine your blood type by causing proteins called ANTIGENS to exist on the surface of all of your red blood cells.

Alleles There are three versions (called “alleles”) of this blood type gene: A, B, and O. A person’s blood type is determined by which allele he/she inherits from each parent.

Pheno vs. Geno The genetic makeup of an organism is called the “genotype”. The “phenotype” is the visible properties of an organism. In this case, the A, B, and O allele combination a person has is their genotype Their blood type is their phenotype.

Dominant vs. Recessive Genes The “A” allele is dominant and so is the “B” allele. They will be “seen” if there is only 1 allele

Example Mr. E got an “A” allele from his dad and an “O” allele from his mom. What is his blood type?

Dominant vs. Recessive Genes “A” and “B” alleles are co-dominant. When both are there, both will be “seen”

Example Ororo Munroe got an “A” allele from her dad and a “B” allele from her mom. What is her blood type?

Dominant vs. Recessive Genes The “O” allele is recessive. If any other alleles are present, even if an “O” allele is there, it will still not be O type. Got to have 2 “O” alleles

Example Ms. Walls got an “O” allele from her dad and a “O” allele from her mom. What is her blood type?

Determining the Genotype The blood type gene has three different alleles: IA is the A allele IB is the B allele i is the O allele

The ABO blood system Genotypes Phenotypes (Blood types) IA IA IA i IB IB IBi IAIB ii

The ABO blood system Blood types A and B have two possible genotypes A blood types can be IA IA OR IAi B blood types can be IB IB OR IBi Blood types AB and O only have one genotype each.

Determining the Genotype Scenario: Mom has the alleles IAIA for blood type and Dad has the alleles IBIB blood type. First, what are the parent’s blood types? What will be the blood type for their child?

Punnett Squares IA IB

Practice A mother has blood Type A and genotype IAi and the father has blood Type B and genotype IBi. Draw a Punnett square to show the possible genotypes of their children. What are the phenotypes of the kids?

Practice IB i IA

Practice A mother has blood Type A and genotype IAi and the father has blood Type B and genotype IB IB. The father doesn’t think the kid is his, so he has a blood test done. The kid’s blood type is O. Is the father right?

What about Rh? Rh is a different gene than the ABO genes. It only has 2 alleles: R is positive r is negative

What about Rh? R is dominant, so only 1 copy is needed to be Rh+. r is recessive, so 2 copies are needed to be Rh-.

To really know blood types, you have to do 2 punnet squares: 1 for ABO and 1 for Rh

Practice Ms. Walls got an r allele from her mother and an r allele from her father. Is she Rh+ or Rh-?

Practice A couple goes on Maury to do a paternity test. The mother has IBi alleles for her ABO and rr alleles for her Rh. The father has IBIB alleles for her ABO and RR alleles for his Rh. If the baby’s blood type is AB+, can he be the father?

Practice A couple goes on Maury to do a paternity test. The mother has IBi alleles for her ABO and rr alleles for her Rh. The father has IBIB alleles for her ABO and RR alleles for his Rh. What if the baby’s blood type is AB-, can he be the father?