Biology project
On DNA Fingerprinting
Index Page no.
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Certificate of authenticity
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Acknowledgement
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What is DNA fingerprint Polymerase Chain Reactions(PCR)
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VNTRs
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Gel electrophoresis Southern Blotting DNA fingerprinting advantages
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Forensic sciences 11 Famous cases solved by DNA fingerprinting 12 1
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Arbitrary Reference
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Certificate of Authenticity 1
This is to certify that “Richard Singh, T” a student of class 12th ‘A’ has successfully completed the research project on the topic “DNA Fingerprinting” under the guidance of Mrs.Bindhu. This project is absolutely genuine and does not indulge in plagiarism of any kind. The references taken in making this project have been declared at the end of this project.
Signature (subject teacher) (examiner)
Signature
Acknowledgement: 2
I feel proud to present my project in biology on the “DNA Fingerprinting”. This project would not have been feasible without the proper rigorous guidance of biology teacher Mrs.Bindhu who guided me throughout this project in every possible way. An investigatory project involves various difficult lab experiments, which have to obtain the observations and conclude the reports on a meaningful note. These experiments are very critical and in the case of failure may result in disastrous consequences. Thereby, I would like to thanks both Mrs.Bindhu and lab assistant Mrs.Meena for guiding me on a systematic basis and ensuring that in completed all my experiments with ease. Rigorous hard work has put in this project to ensure that it proves to be the best. I hope that it proves to be the best. I hope that this project will prove to be a breeding ground for the next generation of students and will guide them in every possible way.
What is DNA fingerprinting?
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DNA profiling (also called DNA fingerprinting, DNA testing, or DNA typing) is a forensic technique used to identify individuals by characteristics of their DNA. A DNA profile is a small set of DNA variations that is very likely to be different in all unrelated individuals, thereby being as unique to individuals as are fingerprints (hence the alternative name for the technique). DNA profiling should not be confused with full genome sequencing. First developed and used in 1984, DNA profiling is used in, for example, parentage testing and criminal investigation, to identify a person or to place a person at a crime scene, techniques which are now employed globally in forensic science to facilitate police detective work and help clarify paternity and immigration disputes. DNA fingerprinting has also been widely used in the study of animal and floral populations and has revolutionized the fields of zoology, botany, and agriculture. Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different that it is possible to distinguish one individual from another, unless they are monozygotic ("identical") twins. DNA profiling uses repetitive ("repeat") sequences that are highly variable, called variable number tandem repeats (VNTRs), in particular short tandem repeats (STRs), also known as microsatellites, and mini satellites. VNTR loci are very similar between closely related individuals, but are so variable that unrelated individuals are extremely unlikely to have the same VNTRs.
Polymerase Chain Reaction (PCR)
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If there is only a small amount of DNA available for DNA Fingerprinting the amount of DNA is increased by using a technique called PCR. PCR is a method of DNA replication in a test tube. • Like All DNA Polymerases Taq polymerase can only add to the 3’ end of an existing nucleotide •A DNA primer that is complementary to the template is used to supply that 3’ end
•
VNTRs (variable number tandem repeats) • After
we
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the DNA amplify it with PCR
• We then treat the DNA with restriction enzymes – cut DNA at specific sequences
and
– Everyone’s DNA is different, so everyone’s DNA will cut at different sites • This results in different sized fragments • The different sized fragments restriction fragment polymorphisms, or RFLPs
are
called length
• We can observe the different sized fragments in an experiment that separates DNA based on fragment size called Gel Electrophoresis • Everyone has genetic sequences called variable number tandem repeats, or VNTRs –
Everyone has amounts of VNTRs
different
– The VNTRs make the different sized RFLPs
Gel Electrophoresis • Fragments of DNA from restriction enzyme cleavage are separated from each other when they migrate through a support called an agarose gel – It is similar to the yummy food Jell-O gelatin
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– It is actually made out of some of the same ingredients
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The size-based separation of Molecules of DNA separate based on size when an electric current is applied to an agarose gel.
• This method is called gel electrophoresis
Gel Electrophoresis
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• The separated DNA fragments are then drawn out of the gel using a nylon membrane
• The nylon membrane is treated with chemicals that break the hydrogen bonds in DNA and separate the strands
• • The single stranded DNA is cross linked to the nylon membrane. – By heat or UV light • Incubate the nylon membrane with a radioactive probe of single stranded DNA complementary to the VNTRs.
Gel Electrophoresis
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• The radioactive probe shows up on photographic film – Because as it decays it gives off light – The light leaves a dark spot on the film
• Different individuals have different patterns of bands – These make up the fingerprint. This Protocol is known as Southern Blotting.
Southern Blotting
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A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization.
DNA Fingerprinting advantages:
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• DNA fingerprints can be used to determine which bone fragments belong to which individual
• DNA fingerprints of children should be similar to the those of parents. DNA fingerprinting can show which individuals are the parents of specific children.
Forensic science
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Forensic science is the application of science to criminal and civil laws, mainly—on the criminal side— during criminal investigation, as governed by the legal standards of admissible evidence and criminal procedure. Forensic scientists collect, preserve, and analyze scientific evidence during the course of an investigation. While some forensic scientists travel to the scene of the crime to collect the evidence themselves, others occupy a laboratory role, performing analysis on objects brought to them by other individuals.[1] In addition to their laboratory role, forensic scientists testify as expert witnesses in both criminal and civil cases and can work for either the prosecution or the defence. While any field could technically be forensic, certain sections have developed over time to encompass the majority of forensically related cases.
Famous cases solved by DNA fingerprinting 12
DNA Fingerprints, stray cigarette helped solve 1997 killing, sheriff
says Amber Gail Creek, 14, was found dead in a Burlington marsh Racine County Sheriff Christopher Schmaling on Tuesday identified James P. Eaton as the 36-year-old Illinois man authorities suspect killed Amber Gail Creek, a 14-year-old runaway girl from Illinois, in 1997. Credit: Racine County Sheriff’s Department The 1997 killing of a 14-year-old girl whose body was found in a Racine County marsh has been solved 17 years later with old fingerprints and new DNA evidence unknowingly provided by the alleged killer, the sheriff said Tuesday. Racine County Sheriff
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Christopher Schmaling identified the suspect as James P. Eaton, a 36-year-old Illinois man, and said he is being held on $1 million bail in the death of Amber Gail Creek, an Illinois runaway. "Over the last 17 years we have dedicated thousands of investigative hours to bring this tragic and senseless murder to its resolution," Schmaling told reporters at a news conference. "Today that day is here." The break in the case stemmed from fingerprints left on the black plastic bag used to suffocate the teen, Schmaling said, and investigators were able to track Eaton and pull DNA evidence off one of his cigarettes. Eaton, a Palatine, Ill., resident, faces charges in Racine County of first-degree intentional homicide and hiding a corpse. Schmaling, who did not take questions from reporters, said Amber's family has asked for privacy. Amber ran away from a stateoperated juvenile shelter in Chicago on Jan. 23, 1997. She attended a party at a motel in Rolling Meadows, Ill., the week of her death and was last seen leaving the party and getting into a luxury car with a man. On Feb. 9, 1997, two men stumbled upon her body while they were searching for hunting sites at the Karcher Wildlife Refuge in the Town of Burlington. She had been sexually assaulted, and her body was found posed with an upraised hand and the greeting "HI" written on the back of her hand, according to Journal Sentinel archives. She was found with a $5 price tag on her arm from a bookstore in the Schaumburg, Ill., area. Investigators spent more than a year and a half examining more than 1,300 missing persons files before they identified
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her, and the case drew national attention at the time, including a profile on "America's Most Wanted" that aired Dec. 12, 1998. Fingerprints taken from the plastic bag and DNA evidence from Amber's body initially yielded no matches, despite the help of the FBI and agencies around the country. Then this year, through new fingerprint identification technology used by a crime lab in Oklahoma, authorities were able to match the prints found on the plastic bag to Eaton's prints, Schmaling said. Eaton had been fingerprinted in Illinois for past, minor offenses, but his name previously had not come up in the Amber Creek case. After learning of the fingerprint match on Feb. 28, Racine County investigators conducted surveillance on Eaton for several days, and when he dropped a cigarette while waiting for a train in the Chicago area, they picked it up for DNA evidence. It matched the DNA found on Amber's body, Schmaling said."Our sense of accomplishment is tempered by the pain and loss we know Amber's family continues to confront every day," Schmaling said. "Our thoughts and prayers remain with Amber's father, mother, other family and loved ones." It wasn't clear whether Amber and Eaton knew each other or how they first would have come into contact. Eaton was 19 at the time of the killing. The sheriff said investigators are still looking for people who can provide with information in the case. They are encouraged to contact the Racine County sheriff's office at (262) 636-3225 or leave an anonymous tip at Crime Stoppers of Racine at (888) 636-9330.
Arbitrary 15 It is the small difference in base pair sequences of DNA that make the phenotypic appearance of each individual unique. An easier and quicker solution to comparing DNA sequences is DNA fingerprinting. In human beings, ninety-nine per cent of DNA base sequences are identical and are known as the bulk genomic DNA. The remaining one per cent DNA base sequences differ and are present as a small stretch of repeated sequences known as repetitive DNA. DNA fingerprinting identifies the differences in this region. To separate both genomic as well as repetitive DNA the process of density gradient centrifugation is carried out. As satellite DNA is lighter and bulk DNA is heavier, so they get separated on the basis of their density. Graphical representation shows bulk genomic DNA as a major peak and repetitive DNA as smaller peaks known as satellite DNA. Satellite DNA is highly repetitive and consists of noncoding sequences. Based on the length of the segment, base composition and number of repetitive units satellite DNA can be classified as mini-satellite DNA and micro-satellite DNA. Mini-satellite is a section of DNA which has a variable number of tandem repeats or VNTR. This step is followed by the hybridisation of the DNA fragments using a radio-labelled VNTR probe. Finally, the hybridised DNA fragments are detected by a technique called autoradiography conducted using an Xray film. Hybridisation with the VNTR probe results in an autoradiogram, which produces several bands of different sizes. These bands provide a characteristic pattern to an individual’s DNA and vary from one
individual to another except in identical or monozygotic twins. Today, 16 the accuracy of the DNA fingerprinting technique has further improved due to the advent of the polymerase chain reaction or PCR, where multiple copies of a single DNA sequence can be made. DNA polymorphism is the guiding principle behind genetic mapping and therefore it helps in the DNA fingerprinting technique. The DNA fingerprinting technique was developed by Alec Jeffrey’s. DNA fingerprinting technique helps in crime investigation, paternity testing, determining genetic and population diversity and studying evolution and speciation.
References www.bcps.org http://www.csun.edu www.nextgurukul.in http://archive.jsonline.com/news/crime https://en.wikipedia.org
