What are STRs and why are they used in human identification?

What are STRs and why are they used in human identification?

• A. Miniature Tandem Repeats; used for paternity testing.
• B. Short Tandem Repeats; highly polymorphic regions used for high discrimination in human identification.
• C. Simple Transverse Repeats; used for age estimation.
• D. Single Tandem Repeats; used for gene expression.

Answer: (B)

Short Tandem Repeats are short DNA sequences, typically 2–6 base pairs long, that occur in repeating units at many locations in the genome. The number of repeats at each location varies among individuals, making these regions highly polymorphic. Because both copies you inherit can carry different repeat counts, STRs are codominant, so you can observe both alleles at a locus. This variability across multiple STR loci provides a powerful genetic profile with a very small chance that two unrelated people share the same combination of repeat counts. In forensic practice, STRs are amplified from small or degraded samples using PCR and then sized by capillary electrophoresis to determine the allele at each locus; combining results across several loci yields extremely high discrimination for identification. This robustness and high discriminatory power is why STRs are the standard tool for human identification.

Short Tandem Repeats are short DNA sequences, typically 2–6 base pairs long, that occur in repeating units at many locations in the genome. The number of repeats at each location varies among individuals, making these regions highly polymorphic. Because both copies you inherit can carry different repeat counts, STRs are codominant, so you can observe both alleles at a locus. This variability across multiple STR loci provides a powerful genetic profile with a very small chance that two unrelated people share the same combination of repeat counts. In forensic practice, STRs are amplified from small or degraded samples using PCR and then sized by capillary electrophoresis to determine the allele at each locus; combining results across several loci yields extremely high discrimination for identification. This robustness and high discriminatory power is why STRs are the standard tool for human identification.