Carlton Comet was killed on February 14th, 2019 while he was at a picnic with several friends. Our job was to find who killed him using forensics to gather evidence.
This project was one of the most interesting STEM projects so far. Our group had to analyze a murder mystery with multiple suspects and lots of evidence. We used skills like DNA fingerprinting and ink chromatography combined with basic forensics to assemble a case to acquire a warrant for arrest of a suspect. Then, we assembled a presentation and used proper legal terminology to present our case and evidence.
Reflection:
This project went very well for me and my group. The project was primarily composed of structured labs in which we found our evidence. Because of this it was easy for the group to focus and work together. I went through several high and low points in the project workflow. One of high points was making it through the project without any real group conflicts. Another high point was our group managing to synthesize all of our information nicely in the presentation. However, my group had some weaknesses/low points. Notably, we were plagued by attendance. On some days our group of 4 would be down to 2 members. Another low point was dealing with group members who were distracted by their Chromebooks and didn't hear instructions. For a STEM project, the Murder Mystery project went remarkably smooth
Concepts:
Chromosomal Disorders:
Chromosomal disorders are disorders that are caused by faulty/defective chromosomes. There are many different types of chromosomal disorders but most of them involve extra, missing, or damaged chromosomes. One example is triple x syndrome, when there are three extra chromosomes. Triple X causes several abnormalities in the body and mind. Chromosomal disorders can be detected when a karyotype is taken of the chromosomes. The main suspect in the murder mystery has triple x syndrome, and this allows them to be identified.
DNA helicase:
The DNA helicase is the enzyme that unzips the DNA strands so that they can be replicated.
RNA primase:
The RNA primase lays down a RNA primer on the DNA strands that are going to be replicated. It does this because the DNA polymerase
DNA mutations:
DNA mutations are when DNA randomly changes during replication because of a mistake made by the enzymes. These often result in new traits because of changes in the genotype. They often have destructive effects if they happen in crucial DNA.
DNA Replication:
DNA replication is when DNA creates a copy of itself. DNA is first unzipped into two strands by the DNA helicase. One strand is the 5' to 3' strand and the other strand is the 3' to 5' strand. These strands make a replication fork, which is the area where DNA replicates. Then the RNA primase leaves a primer on the DNA strand. The RNA primase is needed as a template for the DNA polymerase to start working. The DNA polymerase starts replicating DNA. However, the polymerase naturally works from 3' to 5' so that strand goes through faster and is called the leading strand. The other strand is called the lagging strand because it takes longer. After the DNA has been created the DNA ligase comes in and binds together all of the base pairs so the DNA has structure. Now, the DNA is completely functional. This process leaves the DNA semi-conserved because there is still one half the original strand in each piece of new DNA.
DNA polymerase:
The DNA polymerase is the molecule that makes new DNA base pairs. It reads a RNA primer and then synthesizes DNA bases that get attached to the existing DNA molecules. The polymerase works from 5' to 3' so this affects DNA replication.
DNA ligase:
The DNA ligase is a enzyme that goes through the DNA after the polymerase finishes laying down new bases. The ligase "glues" the DNA together.
Fingerprinting:
Fingerprinting is the process of obtaining fingerprints at a crime scene and using them to identify suspects. Since fingerprints are extremely unique they are a excellent way to identify suspects they are used in forensics. Fingerprints are obtained by dusting a surface to make them visible and then using a adhesive to get the prints. We took fingerprints of the suspects and found Nancy Normal's fingerprint was found at the crime scene.
Genotype:
The genotype is what your gene characteristics are. The genotype can determine what your phenotype, or physical characteristics will look like.
Phenotype:
The phenotype is the physical expression of the genotype. Whether a trait is expressed in the phenotype depends on whether it is a dominant or recessive gene.
Alleles:
Alleles are variations of genes. The allele you have determines what you will look like. In reproduction, each partner contributes one gene. They are generally denoted as two letters, for example, Aa. The capital letter usually means that the gene is dominant, and lowercase means the gene is recessive.
Dominant Genes:
Some genes are dominant, so if you get one copy of a dominant gene then that trait will be expressed in the phenotype.
Recessive Genes:
A recessive gene isn't expressed in the phenotype unless the child gets two copies of it.
Co dominance:
This is when two different dominant genes get paired together. When this happens the phenotype is a mixture of the two.
Incomplete Dominance:
Incomplete dominance is when a gene is not completely dominant over the other. When this happens the phenotype is a mixture of both genes.
Ink Chromatography:
Ink chromatography is a process of separating out the component chemicals/pigments in ink. It is useful in forensics because it can be used to determine what type of pen may have been used at a crime scene. In our project, a note was left behind at the scene of a murder. Using ink chromatography we analyzed the ink and determined that it belonged to the pen of the murderer.
DNA Fingerprinting:
DNA fingerprinting is a laboratory technique used to take a "fingerprint" of DNA. After DNA is isolated it is put in a agarose gel and electricity is run through the gel in a process called gel electrophoresis. This results in the DNA leaving behind a color spectrum. The spectrum can be measured to determine a fingerprint/identifying characteristics to the DNA. Forensic scientists can use this DNA fingerprint to identify a murderer/victim at a crime scene. In our project we used DNA fingerprinting to identify blood on the murder weapon found at the crime scene.
DNA:
DNA, otherwise known as deoxyribonucleic acid, is a molecule that is essential to all life we have discovered so far. DNA contains the instructions for cells to build proteins and it is stored in the nucleus of the cell.
DNA Structure:
The DNA molecule is a double helix, with the double helix being made up of sugar and phosphate molecules, these are known as the phosphate-sugar backbone.
The genetic code itself is made up of base pairs which are attached to the backbone of the double helix. The base pairs are composed of 4 nucleotides which combine together to form the base pair. The nucleotides are made of a phosphate group, a sugar group, and a nitrogenous base. DNA also has directions similar to cardinal directions on a compass. Their is a 3 prime side to the DNA and a 5 prime
side to DNA. The direction matters in DNA replication.
Chromosomes:
Chromosomes are molecules that are meant to hold DNA in a safe place for reproduction. During cell division DNA is organized into multiple chromosomes to store it. In forensics, chromosomes are used to identify unique abnormalities in chromosomes that would identify a person.
Karyotypes:
Karyotypes are the visual appearance of someone's chromosomes. The visual appearance of chromosomes can help determine whether someone has any abnormalities in their DNA, like extra chromosomes or missing chromosomes. This is applicable to forensics, especially in the murder mystery lab. Most of the suspects involved in the murder have chromosomal disorders so they can be identified using karyotyping.
Forensics:
Forensics is scientific techniques applied to crime scene investigation and getting evidence for criminal court cases. In the murder mystery lab we used forensics to analyze our evidence.
Pedigree:
A pedigree is a chart that is used in genealogy. It is similar to a family tree. The pedigree shows the entire family tree including common ancestors. Pedigrees are used to track a traits expression in individuals phenotype. Every individual on the pedigree that has the trait of interest is shaded/marked.