Introduction
Human ABO markers
Blood types and genotypes?
How are ABO alleles inherited by our children?
Blood type & Rh factor calculator
Blood type calculator
Rh factor
Problem set
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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.
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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.
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Blood type
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Possible genotypes
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A
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AA
AO
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B
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BB
BO
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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.
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Blood type
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Possible genotypes
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AB
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AB
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O
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OO
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