Two bold polymorphisms that humans have in addition, to the ABO system. Two alleles LM and LN determine the M, N, and MN bold groups. The dominant allele R of different gene causes person to have the Rh+ (rhesus positive) phenotype, whereas the homozygote, for r is Rh- (rhesus negative). Two men took a paternity dispute to court, each claiming three children to be his own. The blood groups, for the men, the children, and their mother are as follows:
| Person | Blood group | ||
| Husband | O | M | Rh+ |
| Wife’s lover | AB | MN | Rh- |
| Wife | A | N | Rh+ |
| Child 1 | O | MN | Rh+ |
| Child 2 | A | N | Rh+ |
| Child 3 | A | MN | Rh- |
M and N are co-dominant alleles, while the rhesus group is dominant alleles. The ABO alleles are mixed codominance and codominance.
The wife should be A/O; N/N; R/r. Husband could donate O to child 1 and lover would donate A and N to child 2. Both of them could donate the necessary alleles to child 3.