Blood Types – ABO

The Human ABO markers: The A, B, and O alleles

 *** March is American Red Cross Month ***

Human blood type is determined by co-dominant alleles. An allele is one of several different forms of genetic information that is present in our DNA at a specific location on a specific chromosome.

Blood Types

There are three different alleles for human blood type:

Blood types For simplicity,
we call these
IA A
IB B
i O

 Genotypes

Each of us has two ABO blood type alleles, because we each inherit one blood type allele from our biological mother and one from our biological father. A description of the pair of alleles in our DNA is called the genotype.

Since there are three different alleles, there are a total of six different genotypes at the human ABO genetic locus.

Allele from
Parent 1
Allele from
Parent 2
Genotype of
offspring
Blood types of
offspring
A A AA A
A B AB* AB
A O AO A
B A AB* AB
B B BB B
B O BO B
O O OO O

How are blood types related to the six genotypes?

A blood test is used to determine whether the A and/or B characteristics are present in a blood sample. It is not possible to determine the exact genotype from a blood test result of either type A or type B.
If someone has blood type A, they must have at least one copy of the A allele, but they could have two copies. Their genotype is either AA or AO. Similarly, someone who is blood type B could have a genotype of either BB or BO.

Blood type Possible genotypes
A AA
AO
B BB
BO

A blood test of either type AB or type O is more informative. Someone with blood type AB must have both the A and B alleles. The genotype must be AB. Someone with blood type O has neither the A nor the B allele. The genotype must be OO.

Blood type Possible genotypes
AB AB
O OO

How are ABO alleles inherited by our children?

Each biological parent donates one of their two ABO alleles to their child. A mother who is blood type O can only pass an O allele to her son or daughter. A father who is blood type AB could pass either an A or a B allele to his son or daughter. This couple could have children of either blood type A (O from mother and A from father) or blood type B (O from mother and B from father).

 

Inherited Blood type
of child
O from the mother
A from the father
A
O from the mother
B from the father
B

 

Since there are 4 different maternal blood types and 4 different paternal blood types possible, there are 16 different combinations to consider when predicting the blood type of children.

For a blood type calculator visit http://www.biology.arizona.edu/Human_Bio/problem_sets/blood_types/inherited.html

Exterpts from http://www.biology.arizona.edu/Human_Bio/problem_sets/blood_types/Intro.html

The Red Cross

  • Almost 40% of the population has O+ blood
     
  • Patients with Type O blood must receive Type O blood
     
  • About half of all blood ordered by hospitals in our area is Type O
     
  • Type O blood is the universal blood type and is the only blood type that can be transfused to patients with other blood types
     
  • Only about 7% of all people have Type O negative blood
     
  • Type O negative blood is the preferred type for accident victims and babies needing exchange transfusions
     
  • There is always a need for Type O donors because their blood may be transfused to a person of any blood type in an emergency

If your blood type is . . .

Type You Can Give Blood To You Can Receive Blood From
A+ A+  AB+ A+  A-  O+  O-
O+ O+  A+  B+  AB+ O+  O-
B+ B+  AB+ B+  B-  O+  O-
AB+ AB+ Everyone
A- A+  A-  AB+  AB- A-  O-
O- Everyone O-
B- B+  B-  AB+  AB- B-  O-
AB- AB+  AB- AB-  A-  B-  O-
Out of 100 donors . . . . .
 

84 donors are RH+

16 donors are RH-

38 are O+

7 are O-

34 are A+

6 are A-

9 are B+

2 are B-

3 are AB+

1 is AB-

 

 

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