Possible blood types：
Impossible blood types：
The ABO blood group system, one of the most important blood type classification systems in humans, was discovered by Austrian scientist Karl Landsteiner in 1901.
In the ABO system, there are four main blood types：
Blood type is passed down from parents to children, with each parent providing one blood type gene to the offspring.
There are three main alleles in the ABO system：
Of these：
| Blood Type | Possible genotypes of the offspring |
|---|---|
| O | OO |
| A | AA or AO |
| B | BB or BO |
| AB | AB |
| Father | Mother | Children's possible blood types from parental blood types | Blood types impossible for the child |
|---|---|---|---|
| O | O | O | A B AB |
| O | A | O A | B AB |
| O | B | O B | A AB |
| O | AB | A B | O AB |
| A | A | O A | B AB |
| A | B | O A B AB | None |
| A | AB | A B AB | O |
| B | B | O B | A AB |
| B | AB | A B AB | O |
| AB | AB | A B AB | O |
Can two O blood type parents have a type A child?
No. Two O-type parents can only have an O-type child.
Can two AB-type parents have an O-type child?
No. AB-type parents cannot have an O-type child.
Is blood type determined solely by the father?
No. Both parents provide one gene each, which together determine the child's blood type.