What genetic markers are typically analyzed in forensic DNA fingerprinting to establish identity?

• A. Single nucleotide polymorphisms (SNPs).
• B. Short tandem repeats (STRs) or microsatellite loci.
• C. Transposons.
• D. RFLPs.

Answer: (B)

The key idea is that forensic DNA fingerprinting relies on highly variable regions in the genome called short tandem repeats, or STRs. Each STR locus consists of repeat units that vary in number among individuals, so a profile made from multiple STR loci creates a highly unique pattern for almost anyone.

Why STRs are the best choice here: because they have many alleles per locus, they provide a high level of discrimination even with a limited number of loci. They’re co-dominant, so you can see both copies of each locus in a person, which increases the information obtained. STR analysis is PCR-based, producing small DNA fragments that can be amplified even from degraded or tiny samples, and the results are read by precise fragment sizing through capillary electrophoresis. Standard forensic kits analyze a core set of STR loci to build a highly reproducible, publicly comparable profile (as used in CODIS), which gives strong matching power.

In contrast, SNPs have many sites across the genome but only two alleles at each site, so each locus is less informative; you’d need many more SNPs to reach the same level of discrimination. Transposons aren’t the typical markers used in routine human forensic profiling. RFLPs were used in the past but require more DNA, are less sensitive, and are slower and more labor-intensive than STR-based methods.