Lab Report 5
Biology Lab 1100, Section 008
November 28, 2018
DNA, deoxyribonucleic acid, is the genetic material found within a cell that contains the components needed for all living organisms to develop and reproduce. DNA is composed of nucleotides, subunits made up of a sugar-phosphate backbone and a nitrogenous base. In humans, 99.9% of our DNA is the same as the person sitting next to us. Although all human DNA is made up of the same molecules, two people cannot have the same exact DNA sequence. The sequence of DNA building blocks is different in specific regions of the cell, making each person’s DNA unique (Turman, 2001). DNA evidence serves as a reliable tool for crime investigation and can prove either a person’s guilt or innocence. In that 0.1%. that makes us different, DNA can be used to tell individuals apart. In this investigation, Mr. Maximillian Welltodo has been murdered and the goal of this experiment is to find the suspect responsible for his death, so that justice can be served.
It is hypothesized that Mr. Jordan Whatsit is responsible for the death of Mr. Maximillian Welltodo. He was fired by Mr. Welltodo due to accusations of embezzlement and killing him could be an act of revenge. The other two suspects, Alishia Whosit and Alex Slouchabout, do not really have solid reasons to kill Mr. Welltodo. Dr. Whoshit got into a minor verbal argument with him regarding client assignments and Mr. Slouchabout lost a BBQ cook off to him. Although these things could cause them to be angry with Mr. Welltodo, it is highly unlikely that they would go to these lengths to justify the situation.
There was only a small amount of DNA available of each sample, so a PCR (Polymerase chain reaction) was used to make more copies of the DNA sequences. When there is not enough DNA to be analyzed, a PCR helps amplify a sample of DNA by duplicating the strands and producing more. After making more copies of the suspect’s DNA, gel electrophoresis was used to separate the DNA fragments. During this process, the DNA fragments are put into a gel and then placed in an electrical field, where they are sorted into bands according to size. Short strands of DNA travel faster through the gel compared to long strands, allowing the strands to sort themselves.
Using gel electrophoresis, one can tell whether or not the DNA at a crime scene and the DNA of a suspect match. Different individuals will have fragments of different sizes. The bands of DNA created during gel electrophoresis will have a pattern specific to an individual. Having said that, suspects can be eliminated if their DNA pattern does not match the pattern of DNA found at a crime scene (“What is gel electrophoresis”, 2018). The results produced by the gel electrophoresis will help narrow down the suspect list and also help decide on a murderer.
After conducting the experiment, it was decided that Mr. Jordan Whatsit is the one who murdered Mr. Maximillian Welltodo.
In the gel picture, W represents the DNA for Mr. Welltodo, J represents the DNA for Jordan, A presents the DNA for Alishia, G represents the DNA from the wine glass found at the scene, F represents the DNA found under Mr.Welltodo’s fingernails and S represents the DNA for Alex. According to the gel electrophoresis, the DNA sample for Jordan matches the DNA sample from the skin found under Mr. Welltodo’s fingernails. When measuring the two samples, the lines of J and F are the most conclusive. In the police report, it also states that there was evidence of a struggle. This struggle could of lead to Mr. Welltodo scratching Jordan, which is the reason why his skin ended up on his fingernails. The DNA sample for Alishia does not match the DNA sample of either the wine glass or the skin found under Mr.Welltodo’s fingernails. Knowing this information, it is safe to say that she was not present at the crime scene and she can be eliminated from the suspect list. The DNA sample for Alex also does not match the DNA sample for the skin found under Mr. Welltodo’s fingernails. For a moment, it was assumed that the DNA sample for Alex was the same as the DNA sample found on the wine glass. However, after close examination, it was decided that the DNA on the wine glass belonged to Mr.Welltodo, therefore not placing Alex at the crime scene as well. Considering all the evidence, all fingers point towards Jordan being the killer.
When comparing with other groups, the decision of Jordan being the killer was unanimous. Everyone agreed that his DNA sample matched best with the DNA found under Mr. Welltodo’s fingernails. This experiment can be considered reliable, due to the fact that the entire lab class followed the same procedure and, in the end, produced analogous results. Also, when loading the gels, the group made sure that the pipette tips did not touch the gel or container and PCR tubes were labeled in order to reduce error and ensure accurate results. This experiment can also be considered valid. The results accurately measure what it was intended to measure, and the claim is consistent with the evidence provided. Overall, this experiment was successful, and the hypothesis was proven to be correct.