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DNA Fingerprinting

DNA Fingerprinting

Nancy Portillo

Dr. Chen

December 10, 2007

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DNA Fingerprinting

Professor Sir Alec Jeffreys, University of Leicester, researched the new techniques of

molecular biology with human genetics. His plans were to use primitive genetic detection

methods of the time to come across the structures of genes and understand the difference

between people (Newton, 2004, para.3). An early outcome of this research, as mentioned by

Newton: “was one of the first descriptions of a restriction fragment length polymorphism

(RFLP)” (para.3). This RFLP is when DNA-cutting enzymes aim at short DNA sequences, and

cut the genome into pieces. This is a way to identify a person’s genetic code. RFLP proved

inherited variation, but they were difficult to find. Some people have a small DNA change or a

single nucleotide polymorphism (SNP) preventing the enzymes cutting the DNA at that site.

Later, professor Jeffreys collected a lump of seal meat from their freezer and found a

seal myoglobin gene, and inside an intron (non-coding sections of DNA) in that gene were a

repeat of DNA- a minisatellite. These sequences of base pairs are called Variable Number

Tandem Repeats (VNTRs). His team then identified more minisatellites and discovered a core

sequence. This sequence was a piece of DNA that is similar in many different minisatellites.

“‘Using the core sequence, we made a probe that should latch onto lots of these minisatellites at

the same time, says Professor Jeffreys’” (Newton, 2004, para. 9). On a Monday morning in

September 1984, DNA fingerprinting was invented.

DNA fingerprinting is a laboratory procedure that requires six steps. A DNA fingerprint

is constructed by first extracting a DNA sample from body tissue or fluid such as hair, blood,

semen, saliva, and, in rare instances, urine. The sample is then segmented using enzymes called

restriction enzymes that help cut the DNA at specific places. The segments are then arranged by

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size using a process called electrophoresis where the DNA pieces are passed through a gel

(Betsch, 1994, para. 6-9). The segments are marked with probes and exposed on x-ray film,

where they form a characteristic pattern of black bars- the DNA fingerprint (Belair, 2007, para.

1). The process determining the genetic profile using DNA segments was the RFLP, mentioned

earlier. If the DNA fingerprints produced from two samples match, then the two samples

probably came from the same person.

There are, however, environmental factors that play a role in determining whether a

particular sample of DNA can be utilized. For example, moisture, sunlight, bacteria action, and

heat are detrimental to the DNA. Depending on the concentration of these conditions, endurance

of DNA is calculated in weeks or months. As mentioned by Lachter: “DNA is particularly stable

when dried. Once the sample is removed to a dry cool indoor environment, DNA survival in

stains can be measured in years or even decades” (1997, para.2). This allows for scientists to

study blood of living organisms that might have existed for many years. For these reasons, it is

important to conserve the DNA as soon as possible.

DNA fingerprints are useful in several areas of human health care research. DNA

fingerprinting is used to diagnose inherited disorders in both prenatal and newborn babies in

hospitals all over the world. These disorders may include cystic fibrosis, hemophilia,

Huntington’s disease, familial Alzheimer’s, sickle cell anemia, and many others (Betsch, 1994,

para. 11). Early detection of such disorders enables the medical staff to prepare themselves and

the parents for proper treatment of the child. Although, some may find DNA fingerprinting

beneficial, there are other people who may find this part of DNA fingerprinting controversial. To

some people, knowing that a child may have a disorder may lead them to abortion. Since

abortion is so controversial, this use of DNA fingerprinting can be questionable.

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In addition to using DNA fingerprints to link biological evidence, DNA fingerprinting is

also important in the court systems. FBI and police labs around the United States have begun to

use DNA fingerprints to link suspects to biological evidence. As mentioned, blood, semen, hair,

or other items are useful in determining the DNA fingerprints. The evidence left at the crime

scene can be compared, through VNTR patterns, with the DNA of a criminal suspect to

determine guilt or innocence (Biology, pg. 7). VNTR patterns are also useful in determining the

identity of a homicide victim, either from DNA found as evidence or the body itself. Moreover,

there are many challenges on the accuracy of DNA fingerprinting. Some argue that: “Because

DNA segments are rather than complete DNA strands are ‘fingerprinted,’ a DNA fingerprint

may not be unique; large-scale research to confirm the uniqueness of DNA fingerprinting test

results have not been conducted” (Belair, 2007, para. 4). Many concerns on the accuracy are still

in question, but since 1987, more than 150 cases have been decided with the assistance of DNA

fingerprint evidence.

Another important use of DNA fingerprints in the court system is to establish paternity in

custody and child support legal action. Parentage testing cases are numerically the largest user of

DNA testing (Latcher, 1997, para. 6). Most paternity testing is done for financial reasons, to

establish legal responsibility and provide for support. People inherit his or her VNTRs from his

or her parents; therefore, VNTR patterns can be used to establish paternity. According to

Biology: “The patterns are so specific that a parental VNTR pattern can be reconstructed even if

only the children’s VNTR patterns are known” (pg. 8). These patterns have also been used to

confirm legal nationality and, in instances of adoption, biological parenthood. Because testing

can demonstrate conclusively to a man or woman that they are the father/mother of the child,

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many times they not only provide financial support but also emotional support, which can be

vital to the overall development of a child.

There are also moral and ethical implications concerning DNA fingerprinting. The first

issue of DNA fingerprinting in the courts is whether DNA evidence prevents defendants from

getting a fair trial. Many attorneys believe that: “DNA evidence does threaten the constitutional

right to a fair trial” (Lacher, 1997, para. 12). Many times, having the DNA evidence available

will not allow the judge to clearly evaluate the overall issue. Ina addition, lack of financial

availability may lead to a defendant not having the opportunity for further testing and analyzing

of the DNA fingerprints (para. 12). Also, because human beings must interpret the test, human

error can lead to false results. For example, people can be wrongly appointed mother or father of

a child that is not really theirs. For these reasons many people may not agree with the potential

uses of DNA fingerprinting.

Because every organ or tissue of an individual contains the same fingerprint, new

advances in DNA fingerprinting have arisen. The United States armed services have just begun a

program to collect DNA fingerprints from all personnel for use later, in case they are needed to

identify casualties or persons missing in action. This DNA testing, in the future, may be superior

to the blood typing, social security numbers, picture ID, and other methods used to establish

personal identification (Betsch, 1994, para. 10). In addition, in the United States, the FBI has

produced a national database of genetic information called the National DNA Index System. This

database contains “DNA obtained from convicted criminals and from evidence found at crime

scenes” (Belair, 2007, para. 6). These new advances with DNA fingerprinting can be useful to

identify people and to store evidence for further conviction.

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Overall, DNA fingerprinting has afforded us new advances in DNA testing. DNA

fingerprinting is used today in the biological world as well as in the justice system. Because of its

different uses we can potentially find cures for disorders as well as test for paternal fathers and

maternal mothers. In addition, there is now an opportunity to test for inherited disorders both in

prenatal and newborn babies. On the other hand, there are also ethical and moral implications

associated with DNA fingerprinting, from the actual cost to human errors when testing.

Moreover, there are areas for further research such as the accuracy of testing DNA fingerprints,

and matching the DNA with the correct living organism.

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References

Belair, R. R. (2007). DNA fingerprinting. In Microsoft Encarta Online Encyclopedia

2007. Retrieved December 1, 2007. From

http://encarta.msn.com/text_761579857_0/DNA_Fingerprinting.html.

Betsch, D. F. (1994, November). Biotechnology information series: DNA

fingerprinting in human health and society. Biotechnology Training Programs

Inc. Retrieved December 1, 2007, from Academic Search Premier.

Biology. What is DNA Fingerprinting? Retrieved December 1, 2007, from

http://protist.biology.washington.edu/fingerprint/whatis.html.

Lachter, K. (1997). Science and the law: The implications of DNA profiling. Retrieved

December 1, 2007, from http://www.dartmouth.Edu/~cbbc/courses.

Newton, G. (2004, April). Discovering DNA fingerprinting., Retrieved December 1, 2007, from

Welcome Trust, http://genome.wellcome.ac.uk/print.