Which antigen is expect to be in child #3 if the typing results in the family indicate child #1 has B8,12?

The correct choice indicates that child #3 is expected to have the B35 antigen based on the antigen typing results of child #1. Understanding how antigens are inherited is crucial in determining the expected antigen presence in the siblings.

Antigen expression is based on the genetic contribution from both parents. In this case, if child #1 is typed as B8,12, it suggests that they have inherited specific blood group antigens. The presence of antigen B12 may also indicate a combination of parental genes that can shape the profiles of the siblings. Since B35 is part of the B antigen group, if child #1 has B12, there’s a possibility that certain alleles from their parents could enable the expression of a different but related B antigen in another sibling such as child #3.

On the other hand, A1 and A2 are related to the A blood group and wouldn’t typically appear in the typing of a family where child #1 is confirmed to express the B antigen. Thus, the presence of B35, a related B group antigen, would be more aligned with the typing of child #1 and the inheritance patterns that might yield antigen variety among the children.

Thus, B35 emerges as the expected antigen for child #3