Understanding Blood Type Inheritance: A1 Positive When Parents Have A and O

It is completely normal to be A1 positive if your parents have A and O positive blood groups. Blood type inheritance follows specific genetic patterns, and understanding these patterns can help clarify any doubts about blood typing results.

Blood type is determined by the genotypes of individuals, which can be AO for A type and OO for O type. When considering your parents, the possible scenarios are as follows:

Genetic Patterns of Blood Type Inheritance

An individual with A blood type can have genotypes AA or AO, while an individual with O blood type has the genotype OO. When one parent has A and the other has O, the possible combinations are:

From an AA parent and an OO parent: The child can only be A genotype AO. From an AO parent and an OO parent: The child can be A genotype AO or O genotype OO.

Regarding the A1 subtype, it is a specific variant of the A blood group. If you are A1 positive, it means you have the A1 antigen on your red blood cells, which can occur from the inheritance of the A allele from your A parent.

Unusual Blood Type Inheritance

While the vast majority of blood type inheritance follows these patterns, there are rare instances where the result might seem impossible due to certain blood type and genetic conditions:

Parents with O and B blood groups: Children normally inherit O or B blood groups. However, in extremely rare cases, a child with Bombay phenotype (O negate) can result from a mother with O and a father heterozygous for the A group. The occurrence of Bombay phenotype is very low. Parents with O blood groups: In the rare event that both parents have O blood groups, the child could potentially inherit O or O-. However, errors in testing or very rare genetic conditions may occasionally lead to different results.

It is always best to have accurate and repeatable testing in a standard laboratory to confirm blood type results.

Conclusion

Having A1 positive blood type when your parents have A and O positive blood groups is not strange. The inheritance patterns of blood types can indeed result in these outcomes. Always consult with a healthcare professional or genetic counselor to understand your results fully and to rule out any potential errors in testing.