The characteristic of short tandem repeat (STR) DNA that makes it particularly useful for DNA fingerprinting is its high variability among individuals. STRs are repetitive DNA sequences consisting of short repeating units, typically composed of 2 to 6 nucleotides. The number of repeats at a particular STR locus can vary significantly between individuals.
This variability is what allows for the creation of unique DNA profiles for individuals. The likelihood of two unrelated individuals having the same number of repeats at multiple STR loci is extremely low, making it highly improbable for two individuals to have identical DNA fingerprints.
By targeting multiple STR loci and analyzing the variations in repeat lengths, DNA fingerprinting can generate a highly specific and individualized profile. The specific STR loci used in DNA fingerprinting are chosen based on their high variability and ease of analysis.
Additionally, the analysis of STRs is relatively straightforward. PCR amplification techniques can be used to selectively amplify the STR regions from a DNA sample. The amplified DNA fragments can then be separated by size using gel electrophoresis or other methods, allowing for the visualization and comparison of the resulting banding patterns.
The combination of high variability, low probability of identical profiles, and the ease of analysis make STR DNA an ideal choice for DNA fingerprinting. It has revolutionized the field of forensic science and has proven to be a powerful tool for individual identification and establishing biological relationships.