What are Short Tandem Repeats (STRs)?

What are Short Tandem Repeats (STRs)?

• A. Proteins encoded by repeated genes.
• B. Locations on the chromosome that contain short sequences of 3-7 repeating base pairs, ideal for multiplication by PCR.
• C. Sequences of 3-7 bases that occur only in mitochondria.
• D. Large repetitive genome regions of unknown function.

Answer: (B)

Short Tandem Repeats are specific spots in the nuclear genome where a short DNA motif of 3 to 7 base pairs is repeated in tandem. The exact number of repeats at a given spot differs among individuals, making these loci highly polymorphic and useful for identification. PCR can efficiently amplify these regions because the flanking DNA around the repeats provides binding sites for primers, and the length of the PCR product corresponds to how many times the repeat is repeated. Analyzing many STR loci together yields a unique profile for each person, even from small or degraded samples, which is why STR analysis is central to forensic DNA typing. They are not proteins encoded by repeated genes, nor are they restricted to mitochondria; they are repetitive motifs scattered throughout the nuclear genome and are defined by their short repeat units and the varying number of repeats.

Short Tandem Repeats are specific spots in the nuclear genome where a short DNA motif of 3 to 7 base pairs is repeated in tandem. The exact number of repeats at a given spot differs among individuals, making these loci highly polymorphic and useful for identification. PCR can efficiently amplify these regions because the flanking DNA around the repeats provides binding sites for primers, and the length of the PCR product corresponds to how many times the repeat is repeated. Analyzing many STR loci together yields a unique profile for each person, even from small or degraded samples, which is why STR analysis is central to forensic DNA typing. They are not proteins encoded by repeated genes, nor are they restricted to mitochondria; they are repetitive motifs scattered throughout the nuclear genome and are defined by their short repeat units and the varying number of repeats.