DNA fingerprinting lab report

Abstract

The main aim of this paper was to identify the crime suspects suing samples that were obtained from the crime scene. Five crime suspects were approached, and their samples were taken and labeled S1 to S5. Only S2 provided matching characteristics to those found in the crime scene and was therefore held responsible for committing the crime.

Introduction

DNA carries some vital information that is unique for every person. DNA Fingerprinting experiment s majorly have to do with tests that are carried out in various forensic labs to identify various suspects associated with different crimes all over the world. They are also used to assist individuals in identifying their relatives in case of a disagreement on who is biologically related to somebody.

Materials and Methods

The experiment used the following materials, namely; micropipette, pipette tips, microcentrifuge tubes (1.5ml Eppendorf tubes).

The procedure adopted was as follows; the first process was to carry out restriction digestion. I took several Eppendorf tubes, one from each colour and labelled them on top and side with easily identifiable group symbols. I then took ten μL of DNA and dispensed DNA at the bottom of the tube marked with CS (Crime scene DNA). I repeated the above procedure of dispensing the DNA for five suspect tubes labelled S1 to S5. I then added ten μL of restriction enzyme and buffer mixture containing two restriction enzymes named EcoR1 and Pst1.  I then tapped the tubes with my fingertips to ensure a perfect mixing. I later balanced the tubes and carried out a centrifuge for about 5 to 10 seconds to pull down the liquids at the bottom. I then incubated the tubes for 90 minutes at 37 degrees Celsius and later stored the tubes at -20 degrees Celsius..

The second process was the DNA electrophoresis. I carried out the thawing of my DNA samples, after which I added five μL of a sample loading buffer containing five times concentrated blue/green vicious dye to each tube. The buffer sampled was mainly added to help the DNA stay at the bottom when applied. I then mixed the sample well, followed by brief centrifuging to collect the liquid at the bottom. I applied 20 μL to each of the seven wells of the agarose gel. I found the gel submerging under the electrophoresis buffer (1x TAE) in the electrophoresis tank. I then closed the lid and pushed the power button on setting the equipment as a constant voltage of 100 volts. I then ran the equipment for 40 to 45 minutes with some checks 15 to 20 minutes and 30 minutes after the start of the equipment. I observed the dye move about two-third lengths and stopped the electrophoresis machine, after which removed the gel and placed it in the designated box and proceeded with gel staining.

The third process was staining and de-staining by adding a staining dye to cover the gel. I shook the gel for about 2 to 5 minutes and observed the changes in the color of the gel followed by decantation of the dye at the sink. I then proceeded to add enough water about 200ml to cover the gel and allow for distaining. I then closed the top and left the box on a shaker overnight. I then observed the many changes of water to de-stain and took some photographs of the observations.

Results

Figure 1 DNA Fingerprinting Gel

A photo of the observed results was as in the above picture. The results aided in identifying potential crime suspects.The more extended DNA segments were cut into shorter parts with the help of the enzymes. Section L is the DNA size ladder, while the section labelled CS is the crime suspect lane. S1 lane does not have any bands visible, S2-3 lanes consist of few thick and thin bands, and S5 lane consists of few fuzzy and fainted bands at the bottom of the gel.

Discussion

The fingerprinting method of DNA sampling was used to identify crime suspects. The samples were passed through gel electrophoresis for around 45 minutes. The lanes appearing as L consist of the DNA ladder while the lane labelled CS consisted displayed some relationship with the sample that was obtained from the crime scene. The lanes labelled S1 to S5 contained samples belonging to the suspects.

Some sections appeared to be brighter and thicker than others because a certain gene characteristic was being targeted. The other bands appeared thinner because there was a minimal focus on such genes. There were no bands observed in S1, and this may be a result of an error. In S2, a thick band with a distinct thin band having some similar characteristics to those of the crime scene were observed. This shows that S2 had some relationship with the crime scene and thus qualifies to be a suspect.  S3 three showed a thick and matching with samples from the crime scene, but the other two bands in the lane never matched, making S3 not to be a perfect match for the crime scene. S4 had two thick bands with a fainted band at the bottom of the gel, making S4 not to be a suspect. S5 displayed a few fuzzy and fainted bands hence did not match being a suspect

Conclusion

S2 was therefore found to be the suspect at the crime scene because the genes in his/her sample were matching the genes found at the crime scene. DNA fingerprint is therefore used in the various sectors to carry out research and forensic investigation to find out wanted crime suspects(EJ, 2010).

References

EJ, D. (2010, June 12). DNA Fingerprinting. Retrieved from. IDT tutorial: gel electrophoresis. 2010. Available from:: http://cdn.idtdna.com/Support/Technical/TechnicalBulletinPDF/Gel_Electrophoresis.pdf.