DNA Fingerprinting

Michael Jonathan

Mr. Grant Donnan

Science 10.2

10 September 2012

1341 Words

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Table of Contents

1.1 Introduction

1.2. Concepts and Applications of DNA Fingerprinting

1.2.1 The Southern Blot Method

1.2.2 Hybridization Process

1.2.3 Applications of DNA Fingerprinting

1.2.3.1 VNTR’s (Variable Number Tandem Repeats)

1.2.3.2 Paternity and Maternity tests

1.2.3.3 Criminal Cases

1.3 Impacts

1.4 Implications

1.4.1 Ethical

1.4.2 Economical

1.5 Conclusion

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Michael Jonathan

Mr. Grant Donnan

Science 10.2

10 September 2012

DNA Fingerprinting

1.1 Introduction

CSI: Crime Scene Investigation—everyone has watched, or at least heard of, this

infamous show about crime scene investigators tracking down murderers through the use of

sophisticated technology. Although most of the methodology has been heavily dramatized for

television viewers, some techniques applied throughout the show are still true to the facts,

including DNA Fingerprinting. Since its discovery in 1975 by one Dr. Southern, DNA

Fingerprinting, especially the Southern Blot method, has helped forensic scientists to crack the

most the mysterious murder cases, as well as geneticists in connecting familial lineage.

Nevertheless, as with any modern technology, there are always implications involved.

1.2. Concepts and Applications of DNA Fingerprinting

1.2.1 The Southern Blot Method

To begin, one must first understand the concept of DNA Fingerprinting—more

specifically, the Southern Blot method. After DNA is isolated from the nucleus, it is cut to several

pieces of varying lengths through the use of restriction enzymes, which cuts the DNA every time

a specific nucleotide pattern occurs. Through a process called “gel electrophoresis,” which is a

concept similar to polarization, DNA is sorted according to size. Since DNA is slightly negative,

the pieces will be attracted to the positively-charged area and sorted according to size—in

which the shorter pieces, which are able to move quicker than the bigger pieces, are located

closer to the bottom than the bigger pieces. After that, through the use of heat or chemical-

treatment, DNA is denatured, where only one strand is selected from the double helix form of

the DNA. Finally, the gel with denatured DNA is applied to “nitrocellulose paper” and baked to

permanently attach the DNA to the sheet (Brinton and Lieberman, “Southern Blot”).

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1.2.2 Hybridization Process

After the blot is done, a probe is then created by inserting radioactive nucleotides into

artificially-created nicks, or horizontal breaks within a strand of DNA, through the use of DNA

Polymerase. The DNA is then denatured with heat, which not only separates the two strands of

the double helix, but also separates the radioactive strands from the non-radioactive strands

(Brinton and Lieberman, “Making a Radioactive Probe). With the blot and probe ready, it is now

possible to see whether or not the blot contains DNA sequences similar to the probe. The blot is

placed in a plastic bag with the probe and saline liquid, consisting of salt and water, is added

into the bag. When the bag is shaken, the radioactive probes will attach themselves to any

matching complements on the blot (Brinton and Lieberman, “Creating a Hybridization

Reaction”).

The matches themselves do not have to be perfect, but the greater the similarity, the

more hydrogen bonds it will produce with the blot (Brinton and Lieberman, “Creating a

Hybridization Reaction”). To only allow matches with higher “homology”—or number of

similarities—to occur, either the temperature can be made higher or the salinity made lower

The Southern Blot (bottom) as shown through this diagram. The Northern Blot (top) is very similar, but involves RNA instead of DNA and there is no denaturation process as RNA has only one strand (Wiser).

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(Wiser). When this whole process, known as “hybridization,” is finished, and the blot is put up

on X-ray, any areas with similarities will be clearly marked out in black.

1.2.3 Applications of DNA Fingerprinting

1.2.3.1 VNTR’s (Variable Number Tandem Repeats)

Within the DNA, there are two types of material—the exons, which affect organismic

development, and the introns, which carry no genetic information. However, this does not mean

that introns are useless. In fact, they contain between twenty to one hundred “repeated

sequences of base pairs,” known as VNTR’s, which can be used to determine a number of things,

including familial lineages—whether the child is really the child or not, and vice versa—or for

finding the culprit to a criminal case (Brinton and Lieberman, “VNTRs”).

1.2.3.2 Paternity and Maternity tests

Since VNTR’s are hereditary, they must come from either the father or mother, or a

combination, but never from VNTR’s his parents do not have. Thus, VNTR’s, through the use of

DNA Fingerprinting, can reveal whether a child is the true biological child of a couple. A probe,

containing the VNTR in question, is scanned on a Southern Blot through the hybridization

process. Once this is completed, the results are placed on a graph, side by side (Brinton and

Lieberman, “VNTRs”).

For example, the above diagram shows the VNTR’s possessed by “Mom” and “Dad,” the parents being investigated in this case. “D” denotes a daughter, while “S” denotes a son. Clearly, from the table above, Daughter-1 and Son-1 are biological children of Mom and Dad. Daughter-2 is the daughter of Mom and man other than Dad, while Son-2 is most likely an adopted son, since he does not share any VNTR’s with Mom or Dad (Brinton and Lieberman, “VNTRs”).

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1.2.3.3 Criminal Cases

Also, because the VNTRs of a person are unique, unless he is an identical twin, it is

possible to determine the culprit of a crime, especially a murder, through scanning one VNTR

probe on several different blots, and comparing the results, as shown below (Lach and Patsis).

1.3 Impacts

DNA Fingerprinting has helped the world today in many different ways. Besides

increasing the validity and accuracy of investigations as previously explained, DNA

fingerprinting has also helped orphaned children in finding their biological family. When the

military junta reigned in Argentina, it killed over 9000 people. Children made orphans from this

massacre were given to military couples. After the regime fell in 1983, Las Abuelas de la Plaza

de Mayo, an Argentinian group whose goal is to reunite these orphaned children back with their

families, used DNA Fingerprinting as their main method for investigation. Up to today, Las

Abuelas has reunited over 200 children with their families (Gale).

Genetic Fingerprinting has even helped to solve historical ambiguities. On July 16 1918,

The last Tzar of Russia, along with his family, were “shot, doused with sulfuric acid, and buried

The description under the picture provides a clear explanation of how the above VNTR graph can be read. The more similarities that occur from the suspected area of contamination and the suspect’s blood sample, the higher the likelihood that the suspect is the culprit (Lach and Patsis).

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in vast graves” (Gale). Their bodies were never recovered since no one knows the exact location

of the graves. However, in 1989, a mass grave was found containing skeletal shapes formations

akin to what the Tzar and his family would have. Through DNA Fingerprinting, it is found that

they were indeed the last royal family of Russia, and were given a proper burial in 1998 (Gale).

1.4 Implications

1.4.1 Ethical

As seen from the table above, European countries, such as the United Kingdom, Austria,

Switzerland, and Slovenia, enter a suspect’s DNA into the database for any recordable offence

(Norrgard). Especially in the UK, a suspect’s DNA sample is never removed, even for suspects.

To some, this will seem highly unethical because it is likening a thief to a murderer, whose

crimes are very different. This is true, especially in a scenario where the suspect has committed

only a robbery, but is suspected two or three years later for murder because some of his VNTR

matches with the VNTRs of the murderer found at the crime scene. This would be defaming for

the suspect, and since defamation is unethical, it would make this scenario very unethical.

“Characteristics of some national databases” (Norrgard).

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However, consider another scenario, where a man, who has no prior crimes, murders

another man. When the DNA he leaves at the crime scene is searched for within the database,

there will be no match, or worse, other men with similar VNTR’s, who will be suspected for this

murder. Thus, it would instead be also very ethical for everyone’s DNA to be in a DNA database

so there are more possibilities for suspects.

1.4.2 Economical

With the advent of DNA Fingerprinting, the prices for each court case have decreased. In

the past, one court case averaged between 8000 and 10000 dollars for expert testimonials,

while the price for one court case has significantly decreased to only about 1500 dollars per

case, including DNA evidence (Davis). This is economically good for the world as it would allow

more people to bring cases to court, including poorer people who might want to sue for murder

but had previously owned insufficient money.

However, the above scenario shows statistics only in more economically developed

countries, MEDC’s. This scenario would not work in a lower economically developed country,

like Indonesia, because firstly, there are not many universities that offer Forensic Science in

Indonesia, which means that costs for DNA Fingerprinting are still very high. They are so high,

that the National Police have set up a priority system, with cases affecting national security

bring first in the priority, including the Bali bombings (Putra).

1.5 Conclusion

In conclusion, DNA Fingerprinting has successfully helped to solve not only criminal

cases, but also cases on familial lineage and even historical ambiguities. Debates still ensue on

the ethical and economical nature of DNA Fingerprinting. Recent studies show that in the future,

it is very likely that DNA Fingerprints will be used as a “genetic bar code” for personal

identification (Brinton and Lieberman, “Practical Applications of DNA Fingerprinting”). With

this in mind, there is surely a possibility that the money one has in a bank, the lock codes to

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one’s house, and a myriad of other personal liabilities, will be compressed into one genetic

barcode. The question is, will this increase the crime rate, especially in areas concerned with

human death?

Works Cited

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Brinton, Kate, and Kim-An Lieberman. "Creating a Hybridization Reaction." University of

Washington. 04 Sept. 2012

<http://protist.biology.washington.edu/fingerprint/hybrid.html>.

Brinton, Kate, and Kim-An Lieberman. "Making a Radioactive Probe." University of

Washington. 04 Sept. 2012

<http://protist.biology.washington.edu/fingerprint/radi.html>.

Brinton, Kate, and Kim-An Lieberman. "Practical Applications of DNA

Fingerprinting." University of Washington. 04 Sept. 2012

<http://protist.biology.washington.edu/fingerprint/apps.html>.

Brinton, Kate, and Kim-An Lieberman. "Southern Blot." University of Washington. 04 Sept.

2012 <http://protist.biology.washington.edu/fingerprint/blot.html>.

Brinton, Kate, and Kim-An Lieberman. "VNTRs." University of Washington. 04 Sept. 2012

<http://protist.biology.washington.edu/fingerprint/vntrs.html>.

Davis, Chelsi. "Economic Impact." DNA fingerprinting. 04 Sept. 2012

<http://drugdiscovery.webs.com/economicimpact.htm>.

"DNA Forensics." Human Genome Project Information. 04 Sept. 2012

<http://www.ornl.gov/sci/techresources/Human_Genome/elsi/forensics.shtml>.

Gale, Thomson. "Genetics and Society: Impacts of Dna Fingerprinting Research &

Articles." BookRags. 04 Sept. 2012 <http://www.bookrags.com/research/genetics-

and-society-impacts-of-dna-wog/>.

Lach, Christopher, and Thomas Patsis. DNA Fingerprinting. Worcester Polytechnic Institute.

4 Sept. 2012 <http://www.wpi.edu/Pubs/E-project/Available/E-project-011306-

130417/unrestricted/IQP.pdf>.

Norrgard, Karen. "Forensics, DNA Fingerprinting, and CODIS." Nature.com. Nature

Publishing Group. 04 Sept. 2012

<http://www.nature.com/scitable/topicpage/forensics-dna-fingerprinting-and-codis-

736>.

Putra, Sinly Evan. "DNA fingerprint, Metode Analisis Kejahatan pada Forensik." Chem-is-

try.org. 08 Sept. 2012

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<http://www.chem-is-try.org/artikel_kimia/berita/dna_fingerprint_metode_analisis_k

ejahatan_pada_forensik/>.

Wiser, Mark F. "Blotting and Hybridization." Tulane University. 4 Sept. 2012

<http://www.tulane.edu/~wiser/methods/handouts/pwpt/20_nablot_6.pdf>.