Harr Immunology, Serology & Blood Bank (ISBB) 2025 – 400 Free Practice Questions to Pass the Exam

When a genetic marker is absent in a child, but it is understood that this marker should have been transmitted from the alleged father, it indicates a situation where the child's genetic profile does not match what is expected based on the father’s genotype. In this context, the absence of the genetic marker suggests that the alleged father is not the biological parent.

This form of exclusion is termed "indirect/secondary/second order" exclusion because it relies on the absence of genetic markers to infer paternity rather than a direct observation of genotypes. Essentially, the evaluation does not strictly depend on the direct transmission from the father but instead suggests the absence of expected inheritance, leading to the conclusion that he is not the biological father.

The other types of exclusion, like direct exclusion, would involve clear mismatches in genetic markers that can be more straightforwardly observed. Probability and random do not adequately capture the significance of the situation where a specific absence leads to an assertion of non-paternity based on genetic reasoning. Thus, the indirect exclusion reflects a secondary inference drawn from the absence of the marker.