Define an STR and explain why STRs are highly informative for human identification?

Define an STR and explain why STRs are highly informative for human identification?

• A. An STR denotes a gene's location on chromosome
• B. An STR is a short repeating DNA motif; highly variable between individuals, providing strong discriminatory power
• C. An STR is a sequencing technique
• D. An STR is a long non-repeating motif used for species identification

Answer: (B)

A short tandem repeat is a small DNA sequence motif, typically 2 to 6 base pairs long, that is repeated in tandem at a specific location in the genome. The number of repeats at that location can vary greatly between individuals, making each person’s alleles at many STR loci highly unique. Because many STR loci are analyzed together, the combined genotype across them yields an extremely low probability that two unrelated individuals would share the same profile, which is why STRs provide strong discriminatory power for identification. Additionally, STRs are co-dominant, so both alleles at a given locus are detectable (you can see whether someone has two different repeat counts or two copies of the same count). This richness of information is complemented by the fact that the repeat units are short, so PCR can reliably amplify them even from degraded samples, enabling robust profiling in forensic contexts. In contrast, other options describe locations or techniques that Do not capture the defining features of STRs or their purpose in identification.

A short tandem repeat is a small DNA sequence motif, typically 2 to 6 base pairs long, that is repeated in tandem at a specific location in the genome. The number of repeats at that location can vary greatly between individuals, making each person’s alleles at many STR loci highly unique. Because many STR loci are analyzed together, the combined genotype across them yields an extremely low probability that two unrelated individuals would share the same profile, which is why STRs provide strong discriminatory power for identification. Additionally, STRs are co-dominant, so both alleles at a given locus are detectable (you can see whether someone has two different repeat counts or two copies of the same count). This richness of information is complemented by the fact that the repeat units are short, so PCR can reliably amplify them even from degraded samples, enabling robust profiling in forensic contexts. In contrast, other options describe locations or techniques that Do not capture the defining features of STRs or their purpose in identification.