A commercial forensic STR kit determines the sex of the source of a biological sample. Which genetic target does this sex typing rely upon?
- A Amelogenin gene, which has size-different X and Y copies ✓
- B SRY gene on the Y chromosome
- C TDF region within the pseudoautosomal boundary
- D Y-chromosome STR haplotype DYS391
Correct answer: A. Amelogenin gene, which has size-different X and Y copies
Explanation
Commercial multiplex STR kits include primers flanking a six base pair deletion in the amelogenin gene. The X homologue yields a shorter amplicon than the Y homologue, giving one peak in females and two peaks in males alongside the autosomal loci. SRY is the true testis determining factor but is not the marker used in routine STR kits, making option B the tempting but incorrect distractor.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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