Monozygotic twin brothers are suspects in a case where the crime scene DNA matches both of them identically across all 20 autosomal STR loci. Which additional analytical approach can potentially distinguish between them?

• A Testing additional STR loci beyond 20
• B Mitochondrial DNA sequencing of both brothers
• C Y chromosome STR haplotyping of both brothers
• D Analysis of differentially methylated CpG sites in their genomes ✓

Explanation

Identical twins arise from one zygote and share essentially the same nuclear and mitochondrial genome, so adding more STR loci, Y STRs, or mtDNA cannot separate them. After birth, however, their lifestyles and environments drive divergence in epigenetic marks, particularly DNA methylation patterns at CpG sites, which accumulate somatically over decades. Methylation sensitive assays have been used to discriminate between monozygotic twins in forensic casework.

Reference: Butler, Forensic DNA Typing, 2nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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