DNA sample and an individual. This is
DNA fingerprinting/profiling is a technique used to analyze DNA samples to compare individuals and are used to determine if the sample matches an individual. The role of RFLPs in DNA fingerprinting is that RFLPS are used as genetic markers in DNA sequences of a genome. RFLPs (random fragment length polymorphism) is the differences in length of restriction fragments for a whole a genome. They are caused by differences in the restriction sites of a genome, this causes the restriction enzymes to cut them at different lengths. The restriction sites are altered by single nucleotide polymorphism (SNPs), as they are single base pair mutations in the genome.They can be used to uncover differences in a DNA sequence of an individual to determine if they have a disease-causing allele/inherited disease. STRs amplified by PCR is used to create a DNA profile. STRs (short tandem repeats) are short and repetitive DNA sequences in a genome. The sequence may be the same and in the same location between individuals, but the amount of times it is repeated is different. It’s accuracy is higher with comparisons between relatives than strangers. STRs that are amplified by PCR are more commonly use in identification of individuals than RFLPs mainly because STRs are easier to amplify, you can make many copies of it, and a small amount of DNA is needed. RFLPs are longer and can not be amplified, for if you were to run it through gel electrophoresis, you would need a larger DNA sample. That can be an inconvenience for DNA profiling if you only have a certain amount of DNA to work with. The FBI uses a standard of 13 predetermined STR sites, set by the Combined DNA Index System (CODIS) database, to determine a match between a DNA sample and an individual. This is due to the fact that there is so much variations in the human population, that scientists can use 13 standard sites to create a profile that is able to identify a unique individual. Gel electrophoresis is the laboratory technique using a polymer gel to separate different sized DNA restriction fragments. It is important because it separates the fragments based on their size as they move from the negative to positive end, showing a pattern that can be used for comparison and identification. In conclusion, a criminal conviction cannot be made unless there is a match of 13 STR sites between the two DNA samples being compared. The crime scene was a man who had been beaten to death at night after leaving an automated teller bank. There was skin and blood found underneath the victim’s fingernails from fighting off the attacker. The suspect was vaguely identified by a witness, yet he had a visually-similar brother. The witness could not confidently pick a suspect between the two brothers, so a DNA sample from the brothers and from the crime scene evidence had been taken for analyzation and comparison. 7 samples of DNA were amplified by PCR and run the suspect. A predetermined DNA ladder sample is used as the standard to mark the sizes of the molecules that run down the gel. Then, by using two pairs of PCR primers, two amplified sets of the DNA from the first brother, second brother, and evidence DNA are amplified. Looking at the DNA samples after it ran through the gel electrophoresis chamber, the DNA sample Y-2 howed a match between the evidence DNA, thus the criminal is suspect Y.