Discuss STR analysis and the concept of electrophoresis. Explain the use of CODIS in police investigations
The correct answer and explanation is:
Short Tandem Repeat (STR) analysis is a technique used in forensic biology to analyze DNA. STRs are regions of the DNA where a short sequence of base pairs is repeated multiple times. These repeats are highly variable between individuals, making them useful for identifying genetic differences. STR analysis involves isolating DNA from a sample, amplifying the STR regions using polymerase chain reaction (PCR), and then measuring the number of repeat units. The pattern of STRs can be compared across individuals, and these patterns are highly specific, allowing for individual identification.
Electrophoresis is the method used to separate these amplified STR fragments based on their size. During electrophoresis, a DNA sample is loaded into a gel matrix and subjected to an electric field. Since DNA molecules are negatively charged, they migrate towards the positive end of the gel. Smaller fragments move faster through the gel, while larger ones move slower. This results in a separation of DNA fragments, creating a distinct pattern that can be visualized and compared.
The Combined DNA Index System (CODIS) is a national database used by law enforcement agencies to store and compare DNA profiles from crime scenes, suspects, and convicted offenders. CODIS allows for the rapid identification of individuals who may be involved in criminal activities by matching their STR profiles to those already stored in the database. It is a crucial tool in criminal investigations, as it helps link crimes that may have been committed by the same individual, identify suspects who may have left DNA at crime scenes, and solve cold cases. By maintaining a centralized and standardized system of DNA profiles, CODIS enhances the ability of law enforcement to solve crimes efficiently and accurately.