Sarah+DNA+forensics

1) DNA is a nucleic acid in every person that has genetic information on it that is specific to that person. It is found in white blood cells, so anything with white blood cells in it will have DNA. 2) forensic DNA can be used to identify a person from a crime scene from their blood, semen, skin, saliva, or hair because all of these things have DNA in them that is specific to the person 3) DNA profiling: this is a way to determine the identity of a person through the things that they leave behind (blood...). It is also called genetic fingerprinting. In this method, lengths of DNA from the substance are compared to "known" segments of DNA to find a match. In order for the person to be determined, there has to be something to compare it to. (This is why on CSI, they take saliva samples from the people that they are questioning) 4) determining identity from a DNA sample is a five step process: - isolation: takes about 1-4 hours depending on the sample, the sample is extracted from the source and is isolated (the person washes off the excess cellular materials) - quantifying: they have to determine how much DNA that they have extracted and may need to repeat the first step if there is not enough - PCR: polymerase chain reaction, chemicals are added to allow specific parts of the DNA to reproduce many times, 13 locations of DNA are targeted and an instrument cycles between heating and cooling those parts, this takes about 3 hours, there are steps for this process - typing: a machine called a genetic analyzer takes pictures of parts of the DNA as they go through the machine, the result is a picture of spikes or peaks (like an EKG chart) - interpretation: the DNA scientist reviews the DNA to determine if there is a match, a match means that there is a common DNA factor meaning that the person is the suspect and a non-match means that that person can be excluded from the suspect list, this part depends on the quality of the sample being reviewed.
 * heat the sample: initialization
 * denaturation: heats the sample o that the hydrogen bonds split and you are left with sections of DNA
 * annealing: the temp. is lowered to let the primers anneal with the DNA
 * extension and elongation
 * final elongation
 * final hold: it is cooled to keep it stable