The blood group is deter­mined by what types of anti­gens (agglu­tino­gens) are on the sur­face of red blood cells. There are 2 main types of anti­gens — A and B. Accord­ing­ly, on ery­thro­cytes there can be either only type A anti­gens — the sec­ond blood group, or only type B — the third blood group, or both A and B — the fourth group, or they may not be — first group.

The blood type is inher­it­ed accord­ing to the prin­ci­ple of com­plete and incom­plete dom­i­nance and is deter­mined by which blood group genes the par­ents have. There are three types of blood group genes: A — deter­mines the pres­ence of type A anti­gen; B — deter­mines the pres­ence of type B anti­gen; 0 — deter­mines the absence of anti­gens. Each per­son has 2 such genes in the genome. In this case, the fol­low­ing com­bi­na­tions may occur:
00. The first blood group, there are no anti­gens on ery­thro­cytes.

AA or A0. Only type A anti­gens are present, the blood type is the sec­ond.
BB or B0. Type B anti­gens are present, the third blood group.
AB. There are anti­gens of both types, the blood type is the fourth.

In order to assess what blood type your baby may have, it is impor­tant to know that 1 blood group gene is trans­mit­ted from each par­ent to the child. In this case, there are 4 pos­si­ble com­bi­na­tions of these genes. The eas­i­est way to look at this is in the form of a table, in which the top row con­tains the pos­si­ble genes of one of the par­ents, and the left col­umn con­tains the genes of the sec­ond par­ent. As can be seen from the table, which lists the option for a cou­ple with the fourth and first blood groups, it is impos­si­ble to unam­bigu­ous­ly pre­dict which group the baby will have.

Make such a table for your cou­ple. Please note that if one of you has a sec­ond or third blood type, then you need to con­sid­er sev­er­al options for com­bi­na­tions of genes. The table shows the pos­si­ble blood types depend­ing on the geno­type of the par­ents, the blood type is indi­cat­ed in brack­ets.