24. DNA Profiling Some history… First reported in 1984 by Sir Alec Jeffreys of England Made commercially available in 1987 with the opening of a blood testing center
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Editor's Notes
The caller on the 911 line was requesting an ambulance because, he said, he thought the woman in Apartment 204 was badly injured or perhaps dead. The caller did not identify himself. The case turned out -to be murder and later, when the police had a suspect, the district attorney used a spectrograph to check the suspect's voice with the tape-recorded voice of the 911 caller. Bingo! The voiceprints matched and now the DA had some evidence to work with. Many murder cases that hinge on the matching of voiceprints involve tape-recorded 911 calls, according to Steve Cain, one of the nation's leading experts on voiceprint (or spectrograph) technology. "Often it's the murderer who calls," he says, "because he feels sympathy for his victim and he calls to get an ambulance there before the victim dies.”
Size of vocal cavities: he throat, nasal and oral cavities, and the shape, length and tension of the individual's vocal cords located in the larynx. The vocal cavities are resonators, much like organ pipes, which reinforce some of the overtones produced by the vocal cords, which produce formats or voiceprint bars Movement of speech: The articulators include the lips, teeth, tongue, soft palate and jaw muscles whose controlled interplay produces intelligible speech. Intelligible speech is developed by the random learning process of imitating others who are communicating. The likelihood that two people could develop identical use patterns of their articulators also appears very remote. method: a sound spectrograph is used to analyze the complex speech wave form into a spectrogram. The spectrogram displays the speech signal with the time along the horizontal axis, frequency on the vertical axis, and relative amplitude indicated by the degree of gray shading on the display. The resonance of the speaker's voice is displayed in the form of vertical signal impressions or markings for consonant sounds, and horizontal bars or formants for vowel sounds. The visible configurations displayed are characteristic of the articulation involved for the speaker producing the words and phrases. The spectrograms serve as a permanent record of the words spoken and facilitate the visual comparison of similar words spoken between and unknown and known speaker's voice.
Modern-day forensic use of the technique did not start until the late 1960s following its adoption by the Michigan State Police. From 1967 until the present, more than 5,000 law enforcement related voice identification cases have been processed by certified voiceprint examiners. Since 1970, the forensic application of aural-spectrographic voice identification has been reliably applied in the investigation of several thousand cases. While there is disagreement on the reliability of the method under all conditions, there is agreement that voices can be identified and eliminated when the proper conditions exist and the analysis is carefully conducted by qualified examiners.
CODIS stands for Combined DNA Index System, and is a DNA database that is funded by the FBI. It was founded in 1998 and is a computer system that stores DNA profiles created by Federal, State, and Local crime laboratories in the United States, and can be accessed in order to assist investigators in the identification of suspects in crimes.
CODIS first started out as an expansions of the Technical Working Group on DNA Analysis Methods, which was funded by the FBI. It originally consisted of only the forensics index and the convicted offender index, the first of which contained information on different biological materials such as semen, saliva, and blood found at crime scenes. The second of which contained DNA information of those convicted of crimes. Eventually, CODIS expanded and added the Arrestee Index, the Missing or Unidentified Persons Index, and the Missing Persons Reference Index.
Only the NDIS is run by the FBI, the others are left to be run on the state and local levels.
99.9% of humans DNA is exactly the same, however their is enough difference to still identify DNA profiling uses repetitive ("repeat") sequences that are highly variable, [2] called variable number tandem repeats (VNTRs), particularly short tandem repeats ( STRs ). VNTR loci are very similar between closely related humans, but so variable that unrelated individuals are extremely unlikely to have the same VNTRs.
RFLP Analysis (Restriction Fragment Length Polymorphism) utilizes the southern blot test- electrophoresis to separate fragments of DNA, analyze the VNTR loci, however, this process was time and effort consuming and required undegraded samples PCR Analysis- Polymerase Chain Reaction- amplifies the amount of very specific regions of DNA to be compared, can use smaller and more degradced samples STR Analysis- short tandem repeats- can discriminate between unrelated individuals- orften focuses on specific base pairing repeats (4 in a row) AmpFLP- silver staining gel, done in low income countries DNA Family Relationship – half mother, half father, to make zygote with its own DNA profile, compare portions to determine paternity, maternity Y Chromosome – paternity Mitochondrial – cells contain many copies of MtDNA and only few copies of Nuclear DNA, can use very degraded samples, sequence this DNA and compare to a reference
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