DNA Does Not Lie
- 1. DNA Does Not Lie Genes, DNA and Criminality The way one looks and behaves is part genetic and part environmental. The genes contained by the individual shape the way we look and act. You may be familiar with the saying “you look like your grandmother” or “you have your father’s eyes”. This is true because, genes are very powerful molecules that gear how we look on the outside and act internally. Genes are contained in chromosomes made up of DNA and proteins. (Deoxyribose nucleic acid the scientific name) DNA is the blueprint for all living things. It contains the master plan by which cells run our bodies with the help of proteins coded in our DNA. A gene is a length of DNA which has a specific sequence of smaller molecules; know as nucleotides (A, T, G, and C) for Adenine, Thymine, Gaunine and Cytosine. The sequence in which the nucleotides are arranged helps make the coding DNA molecule, which is read in the cell to govern our life. DNA molecules with the help of enzymes make copies of itself and carry life’s information from parent to offspring. Each individual will have a unique set of genes made from the letters of life (A, T, G, C) in DNA, which one gets from his/her mother and father. So it is safe to say one acts the way his/her genes (DNA) dictates. Scientists have done much work in how genes affect social behavior and also developed numerous forensic methods. DNA Fingerprinting One of the most powerful tools used by scientists in criminal investigations is DNA fingerprinting also known as DNA testing or DNA profiling. DNA fingerprinting was accidentally developed by Dr. Alec Jeffreys in 1984, and has helped power many areas of investigative biology, forensics and legal medicine. Today it is used as a technique to solve cases such as paternity maternity issues, solving rape and murder cases, identification of remains of soldiers, and also to give evidence that one was at the scene of the crime. It has also helped other branches of science such as evolutionary biology, plant genomics, testing of food samples and genetics. A DNA profile of the individual is an encrypted number set which is a clear reflection of the organism’s genetic makeup. It can be used to identify an individual organism (person in case of a human being). 99.9% of human DNA is the same in each individual. The remaining 0.1% has a set of sequences (A, T, G, C code of life in their DNA) which is so unique that it can help identify an individual with a great degree of accuracy. The only problem would be in monozygotic (identical) twins. Human DNA that codes for various functions is present in 20,000 to 25,000 known genes. A large part of the DNA has non-coding genetic information junk DNA (not used to make proteins). Numerous changes take place in this part of the DNA aiding in the survival of the species. Random variations as often as 1 in 200 alphabets (nucleotides A, T, G, C) take place in the non-coding junk DNA. DNA profiling takes
- 2. advantage of this unique in the junk DNA. The junk DNA often as variable number of tandem repeats (VNTRs), sequence repeated in the Junk DNA. DNA fingerprinting uses these variable number tandem repeats (also known as VNTRs) for analysis. Short tandem sequences or short repeats are very often used. The point where the sequences lie in closely related individuals is similar, but two unrelated individuals will have some difference in their VNTRs, STRs, thus, aiding in clear identification. The Technique: Just how is it done? Samples from the scene of the crime (blood, semen hair, body fluids or even saliva) are collected. These samples have the suspects DNA in them and serve as a good way of finding who was involved in the crime. This collection of sample must be done carefully. This requires the police or detectives to have proper training for admission as proof in a court of law. A reference sample is collected from the each individual suspect for further analysis and is compared to those which were collected and persevered from the crime scene for a clear genetic match. Once all the samples are collected they are labeled and carefully handled in a certified laboratory with certified and trained scientist operating there. The sample may be even a single hair strand or cell. In case of small samples it is taken and amplified by using a technique known as polymerase chain reaction. Here a single strand of DNA is chemically multiplied into numerous copies to assist in increasing the sample volume. In case of abundant samples, it is cleaned and the DNA is extracted. The extracted DNA is cut at specific places with a restrictive enzyme. The enzyme breaks the long DNA strands into tiny pieces at a specific point on the DNA. The pieces of DNA can then be separated according to their size is run on an electrophoresis gel (technique used to sort the pieces of DNA). Each piece of DNA forms a band on the gel. The smallest pieces travel the furthest and are therefore closest to the bottom of the gel. The larger pieces travel shorter distances and are closer to the top. Thus, a unique imprint can be made from the run sample. Since, the VNTRs will be different in individuals one can use various restrictive enzymes that cut the DNA at specific locations and get a unique profile on the gel. The unique pattern is photographed once the pieces of cut DNA are sorted on the gel. Depending on the individuals genetic makeup one will get a unique graph of the broken pieces of DNA. This photograph is compared to that of the reference individuals and can be compared to the DNA from the crime scene samples. Hence, if a match is made one can with 1 in a billion certainty claim the criminal was present at the crime, or was responsible for rape etc. Some Forensic Cases: Since 1985 the technique for DNA analysis has been used in The United States and Europe millions of times. The first case when DNA fingerprinting got its fame, took place in England. In 1986 the Scotland Yard was investigating two rape and murder cases which were spaced 2 ½ years apart. After their efforts a psychiatric patient by the name of Richard Buckland was picked up and he confessed to the court that
- 3. he did the crimes. His semen sample was sent to Dr. Jeffreys for analysis. The verdict of Dr. Jeffreys’ genetic tests shocked everyone. The scientist stated Buckland was not the serial rapist, but the person who did the crimes based on samples from the crime scene was the same person. Buckland became the first person to be cleared by DNA analysis of a crime. Latter a drive in the villages North of London began collecting blood samples which were analyzed. It led to the discovery of Collin Pitchfork. He was charged with the crime after his plan to pass his friend’s (Kelley) blood sample as his own was blatted out by drunk Kelley in a bar. Pitchfork was finally convicted. This case gave the push for DNA fingerprinting to be used in forensics. Today the technique with PCR and modern protocols is now admissible as proof in a court of law. Another case where DNA profiling was used in court in not too distant memory was the O. J. Simpson case of 1994. The evidence against O. J. Simpson using DNA fingerprinting was strong but because of faulty sample collecting techniques by the police led to his acquittal. Another memorable event (terror attack) that required DNA fingerprinting, took place on September 11th, 2001 at the World Trade Centre. Numerous forensic tests were done to help identify the people who perished at the Twin Towers, in New York. Since 1987 more than 150 cases have been decided in the U.S. with the assistance of DNA profiling, because a link to the suspect in the case was found with compared DNA from the blood, clothing, semen or hair at the crime site. Disadvantages of the Technique: The sample must be collected properly to be presented in legal cases. This would require trained personnel and certified techniques according to legal protocols. The techniques used require standardization and quality control. These involve great cost hence there are only a few reliable laboratories that are certified to do these tests. There is a 1 in 50 billion chance of 2 individuals having similar sequence. Applications of DNA Profiling: Despite disadvantages it has helped man in various branches of biology. It is used in criminal identification, solve case of immigration, civil disputes, war crimes, disaster management, to solve issues of paternity, or even detect disorders (such as cystic fibrosis, sickle cell anemia, thalasemia, hemophilia, Huntington's disease, Alzheimer’s (Familial Type), huntington's chorea, and marfan's syndrome to name a few) in new born children, hence allowing early precaution and intervention by the physicians. DNA finger printing has helped isolate genes of various disorders by using family history as a way to find the specific genes of inherited disease in the population. The identification of these genes is important to medicine as it allows new drugs to be developed, tests to be done and aid is medical discovery science.
- 4. Besides medicine, DNA fingerprinting techniques have also helped in studying evolution, study and identification of disease causing bacterial strains, and even aids in crop science to name a few. With the aid of science of DNA man has benefit in numerous ways, and we can safely say DNA does not lie.