In a homicide investigation, the crime scene STR profile matches no entry in the national database. Investigators request analysis aimed at predicting the unknown offender's likely eye and hair colour from the DNA itself. Which class of markers makes this possible?
- A Autosomal STR repeat number variants at pigmentation gene loci
- B Single nucleotide polymorphisms associated with genes controlling melanin synthesis and distribution ✓
- C Mitochondrial DNA hypervariable region sequences
- D Y chromosome STR haplotypes
Correct answer: B. Single nucleotide polymorphisms associated with genes controlling melanin synthesis and distribution
Explanation
Externally visible characteristics such as iris and hair colour are predicted from panels of SNPs in genes governing pigmentation, including HERC2, OCA2, MC1R, and SLC45A2, using validated systems such as HirisPlex. STR repeat counts and mtDNA sequences do not encode visible traits, and Y STRs only inform paternal lineage. This phenotype guided intelligence helps prioritise suspects when no database match exists.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.