Essay- A brief history of DNA fingerprinting.
What is DNA fingerprinting
DNA fingerprinting is a genetic method that uses biological samples (blood, hair, nails, saliva) to allow the identification of distinct patterns within their DNA. DNA fingerprinting allows to identify an individual via their sequence of DNA nucleotides, this allows for comparisons of DNA between individuals or different organisms and species. Human DNA has 3 million base pairs only identical twins have 100% the same DNA base pairs. To compare the differences between two strands of DNA we look at microsatellites which are short base sequences of DNA around 10-60 pairs. Minisatellites in the human genome is detected by DNA fingerprinting to produce a unique pattern for a certain individual, this was invented in 1984 by Professor Sir Alec Jeffreys, he proposed that you were able to detect variations in human DNA via minisatellites.
Sir Alec Jeffrey’s
Sir Alec Jeffrey’s designed and created genetic fingerprinting. He studied biochemistry and genetics at Oxford University, he then moved to the Netherlands and received a fellowship at the University of Amsterdam. Furthermore, Sir Alec Jeffrey’s was one of the first scientists to discover split genes, this then caused him to move to Leicester University into the department of genetics. Moreover, he became the Professor of genetics (Investigating genetics).
The basic structure of DNA
Figure one above shows a deoxyribonucleic acid (DNA) which is a macromolecule that stores genetic material, it is coiled into helix structure, consisting of two sugar-phosphate back bones (which are the same in every DNA molecule). However, the sequence of DNA nucleotides is unique for all the different organisms in the world. The genotype is determined by the order and sequence of the DNA nucleotides, the four different nucleotides are guanine which forms 3 hydrogen bonds with cytosine, whereas, adenine which combines to form 2 hydrogen bonds with thymine. The two sugar-phosphate back bones run antiparallel to one another, this organisation is important as it increases the accuracy of DNA replication to occur in a cell. Replication of DNA is bidirectional which is an appropriate replication system as it reduces the risk of error during replication. In a eukaryotic genome 109 to 1011base pairs per genome so that the error rate is low to reduce the risk of any lethal mutations, however, it allows for genetic variation to take place. Furthermore, a gene is a section of DNA that are compact into units known as chromosomes, the human cell consists of 23 pairs of chromosomes which provides a basis of inheritance from parent to offspring. To conclude, cystic fibrosis is a hereditary disease, which can be passed on from parent to offspring, if both parents are recessive heterozygous carriers of the gene. Cystic fibrosis is caused by a mutation in the CFTR channel protein, this then prevents the channel protein to carry out its main function of allowing the transport of chloride ions in and out of epithelial cells (Human Physiology).
How DNA fingerprinting takes place
The human genome contains regions called VNTR’s (variable number tandem repeats). These regions vary between individuals in the number of tandem repeats (their length). Every human has two copies of each VNTR one on each homologous chromosome, which is inherited from each parent (AQA).
Method of DNA fingerprinting
The first stage in genetic fingerprinting is to extract the DNA sample from either blood or a hair cell. PCR (polymerase chain reaction) clone’s DNA fragments to amplify the VNTR regions within the DNA sample. Were restriction endonucleases are used to hydrolyse DNA into fragments which then produce blunt ends that cut outside of the VNTR regions. Furthermore, gel electrolysis is used to separate the DNA fragments according to their size, as DNA has no colour a fluorescent tag is added to all the DNA fragments (usually to the primers) this allows the DNA to be viewed under the microscope using a UV light (AQA book). Figure two shows the DNA fragments in bands and identifies that suspect two committed the crime as they match the DNA found at the crime scene.
3290570280353Figure two- https://www.bing.com/images/search?view=detailV2;ccid=fZPXgnhx;id=9E5F2C60A5F7A63D6F63E1953B4690DF698A03DB;thid=OIP.fZPXgnhxjjJI97c9XNJpcAHaFy;mediaurl=http%3a%2f%2fgeneed.nlm.nih.gov%2fimages%2fdna_fingerprinting_sm.jpg;exph=394;expw=504;q=DNA+Fingerprinting;simid=608035619427977628;selectedIndex=7;ajaxhist=0
4000020000Figure two- https://www.bing.com/images/search?view=detailV2;ccid=fZPXgnhx;id=9E5F2C60A5F7A63D6F63E1953B4690DF698A03DB;thid=OIP.fZPXgnhxjjJI97c9XNJpcAHaFy;mediaurl=http%3a%2f%2fgeneed.nlm.nih.gov%2fimages%2fdna_fingerprinting_sm.jpg;exph=394;expw=504;q=DNA+Fingerprinting;simid=608035619427977628;selectedIndex=7;ajaxhist=0
-5956302552700Figure 3- http://slideplayer.com/slide/9910665/32/images/25/PCR+Amplification+Exponential+Amplification+of+template+DNA.jpg
00Figure 3- http://slideplayer.com/slide/9910665/32/images/25/PCR+Amplification+Exponential+Amplification+of+template+DNA.jpg
Figure three on the left shows Polymerase chain reaction and how many of the wanted gene can be copied. Therefore, to use PCR DNA is amplified outside of the living organism via vitro cloning. PCR can make millions of copies of DNA fragments within a few hours, via going through stages. The first step is a mixture that contains DNA sample, primers, free nucleotides and DNA polymerase (primers are short pieces of DNA that are complimentary to the bases at the start of the fragment that is going to be copied). Furthermore, new strands are created by the enzyme DNA polymerase which originates from bacteria that are found in hot springs so that they can withstand high temperatures without denaturing. Step two, the DNA mixture is heated up to 95 degrees to break the hydrogen bonds between the two strands of DNA, the mixture is then cooled so that the primers can bind to the DNA strands at 50 to 65 degrees. In the third stage, the mixture is reheated to 72 degrees, this allows the DNA polymerase to work within the right conditions. Free DNA nucleotides bind to the template strand via specific and complimentary base pairing, producing two original and two new strands. These step processes carry on repeating using the new and the original strands to act as the template until enough DNA nucleotides have been copied (AQA book).
The image above represents gel electrophoresis. Firstly, the DNA fragments are placed into a buffer solution which conducts electricity through the gel, you can see in the image the positive electrode and negative electrodes are at opposite ends of the gel. The DNA fragments are negatively charged so this causes them to move to the positive electrode at the opposite end of the gel. The shorter DNA fragments move through the gel faster, this causes the DNA fragments to separate according to length, this results in a pattern of bands. After a while the electrodes are turned off and the gel is placed under a UV light, which will display bands. A known DNA ladder may be added as well to show the DNA fragments of a known length for comparison, if the bands are found at the same location in the gel this means that they have the same number of nucleotides and the same number of VNTRs, this shows a match (AQA Book).
Ethical implications of genetic fingerprinting
As technology is becoming cheaper and more readily available it is difficult to distinguish a boundary of personal harm being caused.
An advantage of genetic fingerprinting allows for the human genome to me mapped and can be used to identify diseases which this individual may be in risk of, for example, BRCA1 gene increases the risk of breast cancer which can be influenced by the onset of the individual’s environment. However, the implication is that it can not predict whether the individual will develop the condition in the future or at what age it may onset, furthermore, it can not state the severity of the condition and the quality of life it could affect.
Another ethical implication in genetic fingerprinting is confidentiality of an individual’s genome, it would be considered unethical if it was stored in a database without any use, due to many officials having access to DNA profiles. Therefore, for DNA fingerprinting to be considered ethical, officials need to ensure confidentiality of their DNA database.
An advantage of DNA fingerprinting can be used to track inheritance around the globe, this can reduce racism in the future due to family trees being mapped.
DNA profiling is useful during crime scenes, it can increase accuracy in catching the possible suspect of who committed the crime via DNA profiling. This is done by collecting a sample of DNA at the crime scene, such as, hair, fingerprint or blood, if the DNA coding from the crime scene matches a DNA profile on the database then that person is responsible for committing the crime. DNA databases have increased accuracy of catching the suspect in 60% of UK’s crime cases.
DNA profiling can also increase globalisation around the world, as it allows information of DNA databases to be shared between different countries, this allows them to identify whether the criminal has committed more than one crime in different countries.
Lastly, another ethical implication is that if the national DNA database carries on increasing in data, this can lead to false accusations of criminals being made and innocent individuals being accused and put into prison.
Case study on Colin Pitchfork
In November 1983 a young 15-year-old school girl called Lynda Mann, was raped and murdered in Leicester England. 3 years after her death the killer had still never been caught, until Dawn Ashworth (another 15 year-old-girl) was raped and murdered within a mile of where Lynda Mann’s body was found. This caused the police to believe that both rapes and murders where linked to the same killer. A young 17-year-old boy (Richard Buckland) confessed to the murder of Dawn Ashworth and was arrested in 1986, however, he denied any involvement in the murder of Lynda Mann, this caused the police to ponder the investigation of both murders.
Furthermore, the police heard of Alec Jeffreys discovery at Leicester University, this caused the head investigator to ask Alec whether he would be willing to help link the young boy to both murders. Alec Jeffrey found that the young boy did not commit any of the murders, however, he found that the same person did kill both young girls, meaning that, young Buckland was released from all murder charges. The question they still ask is why Buckland confessed to raping and killing young Dawn Ashworth.
As a result, of Alec’s findings he administered the police to collect blood from 6,000 men across 3 small villages, surrounding the murder sites. During this investigation a local baker named Colin Pitchfork persuaded a friend to take his place during the blood tests, Colin even went to the extent of altering his own passport. This passport was then used for his friend’s identification and his excuse was he did not want his wife to know he was having an affair. The police were then made aware of the deception which took place and demanded a blood sample from Pitchfork. DNA fingerprinting was then used to catch Colin Pitchfork as the rapist and killer of the two young girls, meaning that, he was sentenced to imprisonment for both murders and DNA in crime investigations had begun (tandfonline).
A second example of a case study were genetic fingerprinting has been used.
Roy Criner was convicted of murder and rape of Deanna Ogg on the first of May 1990. He was then sentenced to 99 years of imprisonment. Roy Criner seven years later asked for a DNA test to be conducted and they found that Roy’s semen did not match the semen of the rapist. As a result, Roy faced a new trial at Texas court and was accused of having consensual intercourse prior to being raped and stated that he might not have ejaculated or he may have worn a condom so that there were no traces of his sperm. Meaning that, Roy remained in prison until three years later a cigarette butt was tested from the crime scene. The DNA results showed that the DNA matched the semen left on Deanna’s body did not match Roy’s semen. Therefore, Roy Criner’s charges were removed and he was set free. This shows that, DNA profiling is changing prison systems and people’s lives as Roy Criner would have spent his whole life in prison even though he was found not guilty (Sir Lanka).
To conclude, DNA fingerprinting will change future science and medicine, due to it being able to map genetic mutations which can occur in an individual’s genome. Therefore, it increases quality of life for people around the globe. Furthermore, it also helps for criminals to be identified and reduces the risk of an innocent person to be put into prison. Nevertheless, DNA fingerprinting is important in today’s society as crime being committed is increasing each year, meaning that, it helps with police investigations in order to catch the criminal who committed the crime.
Silverthorn,U,D.2010.Human Physiology an integrated approach.5th edition. San Francisco: Pearson Benjamin Cummings.
Department Of Genetics.2013. The man behind the DNA fingerprints: an interview with Professor Sir Alec Jeffreys. pdf https://investigativegenetics.biomedcentral.com/articles/10.1186/2041-2223-4-21accessed 17th November2018
BIBLIOGRAPHY Napper, R. 2000. A National DNA Database the United Kingdom Experience. Australian Journal of Forensic Sciences, , 32(2), pp. 65-69.
Fernando,R. 2010. A national DNA database for Sir Lanka. pdf http://www.pdn.ac.lk/foren/issues/vol1-1/art2.pdf Accessed 25 November 2018
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