See also: blood type and blood group diet
The tables proposed in this article allow you to quickly calculate the compatibility of a subject's blood group with that of their parents.
The first scheme allows us to establish the possible blood group of a child knowing the blood group of the mother and the alleged father.
To consult the table find the column corresponding to the father's blood group and search through the various lines that make up that relating to the mother's blood group.
| Blood Group of the Father | ||||||
| TO | B | AB | 0 | |||
| Mother's blood group | TO | A or 0 | A, B, AB, or 0 | A, B, or AB | A or 0 | The child's blood type must be: |
| B | A, B, AB or 0 | B or 0 | A, B, or AB | B or 0 | ||
| AB | A, B, or AB | A, B, or AB | A, B, or AB | A or B | ||
| 0 | A or 0 | B or 0 | A or B | 0 | ||
If for example the father's blood group is 0 and the mother's is B, the child will have blood type B or 0.
In some cases (mother with blood group A and father with group B) the ability of the test to establish paternity is very low (the child can have each of the 4 possible blood groups).
The second scheme allows us to trace the father's blood group knowing that of his son and mother.
To consult the table look for the column corresponding to the child's blood group and choose the one that intersects the mother's blood group from the various lines that make it up.
Some boxes have been obscured because such combinations are not possible (a child cannot have AB blood group if the mother is a carrier of group 0).
| Blood Group of the Son | ||||||
| TO | B | AB | 0 | |||
| Mother's blood group | TO | A, B, AB or 0 | B or AB | B or AB | A, B, or 0 | The father's blood type must be: |
| B | A or AB | A, B, AB or 0 | A or AB | A, B, or 0 | ||
| AB | A, B, AB or 0 | A, B, AB or 0 | A, B, or AB | |||
| 0 | A or AB | B or AB | A, B, or 0 | |||
NOTE: only in some specific cases the blood group test can confirm or exclude unequivocally a presumed paternity. Only DNA analysis can therefore provide a 100% safe result. Although very rarely, genetic mutations can change the rules that even "impossible" children (eg group A or B from parents 0) can become "possible".
These tables could raise some doubts about some specific cases. Some might wonder, for example, why two parents with blood group A can give birth to a child with blood group A or 0. To answer this question, it is necessary to clarify some basic concepts of Mendelian genetics.
A person's blood group is determined by the presence of two alleles. An allele is an alternative form of a given gene. For example, a gene that controls the "hair color" character in an animal can exist in two alleles: the "light-haired" allele and the "dark-haired" allele.
