In a paternity dispute, the alleged father is unavailable for testing. DNA profiling using autosomal STR markers is performed on the child, the mother, and the paternal grandfather. Which genetic principle allows kinship inference in this scenario?

• A Mitochondrial DNA inheritance exclusively from the mother
• B Y-chromosome STR haplotype shared between paternal male line relatives
• C Autosomal STR alleles are passed from father to child and must be present in the paternal lineage ✓
• D X-linked microsatellites are diagnostic for paternal contribution

Explanation

Autosomal STR alleles are inherited one copy from each parent; child alleles not accounted for by the mother must come from the father. When the alleged father is unavailable, comparison with his known relatives (grandfather) uses the principle that obligate paternal alleles should appear in the paternal lineage, allowing a statistical kinship likelihood ratio to be calculated. Y-STR haplotyping (B) is useful for male-line kinship but cannot alone establish paternity; mtDNA (A) only traces matrilineal descent; X-linked STRs (D) are not the standard tool for these calculations.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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Written and medically reviewed by the StethoPrep medical team.