Genes and DNA!

            We are in the midst of creating a science symposium for the Grade 7’s of our school. It involves the performing of a lab, presenting of information, and assessing of skills obtained. My partner and I are doing our project on the subject of Genes and DNA, and performing an experiment that will be extracting the actual DNA from strawberries using the scientific properties of dish soap, rubbing alcohol, and DNA.

We learned many interesting things while doing our research. A human body is made up of 50 000 000 000 000 cells that all function differently in our bodies. Inside cells are a nucleus which contains 99.9% of our genes. Genes are a part of long molecules in our bodies called DNA (Deoxyribonucleic Acid). If you lined up your entire DNA, it would be at least 6 feet in length. DNA is composed of sugar, phosphate, and 4 bases (Adenine, Thymine, Cytosine, and Guanin) which determine your genetic code. Genes determine how a cell functions and what traits it expresses. The molecules of DNA with your genes are organized into chromosomes; all species have different numbers of chromosomes. Interestingly, humans have two sets of 23, chimpanzees have two sets of 24, chickens have two sets of 39, and bananas have two sets of 11. It is also known that humans share 98.5% of their DNA with chimpanzees, and 99.5% with every other human. This made me realize how alike each person actually is, even though people usually focus on the differences. SNP’s are the imperfections in our base pairs of chromosomes that make us different from one another. It is a variation in base pairs, of Single Nucleotide Polymorphism. Sometimes a single base pair gets added, left out, or substituted. When a base pair gets substituted, this is called an SNP. There are around 10 million SNP’s in the human genome which account for the differences between everyone on Earth. They can affect our physical traits, how we acquire diseases, or how we respond to medication. The number of differences between your DNA and your friend’s DNA can tell you how closely you are related.  Our observable traits are called phenotypes, and result from a combination of your genes and your environment. This interaction starts in the womb and continues through your life. Differences, for example, in height, are determined mostly by genes, but nutrition does have some effect. Weight is also determined by both genes, but more by your diet (environmental). It is less understood how genes determine your personality. Scientists are learning how SNP’s help to determine or affect your phenotype.

DNA is not only important to us because it makes us who we are, but it can also be studied by scientists, who can use the DNA in your body to help it function properly, to make new medicines, to genetically modify foods, or to figure out a suspect of a crime. This can be done through a process of DNA extraction. We will then be performing an experiment that will help with further understanding of what DNA actually is. In the experiment, the Grade 7's will be ablt to visibly see clumps of DNA that exist in strawberries and that contain all the genetic material essential to make a strawberry a strawberry. Strawberries from the grocery store will be used because they have 8 copies of each chromosome, so they are a great source of DNA. During this experiment, we are going to break open the cells of the strawberry and then separate out and clump together the DNA from the strawberry cells so that it is visible to the eye. In order to burst open the strawberry cells so that the DNA is released, we are going to be adding an extraction solution containing dishwashing liquid, salt, and water. Because DNA is not soluble in alcohol, the DNA strands will clump together so that we will be able to see it.

http://ucbiotech.org/resources/display/files/dna_extraction_from_strawberrie.pdf.  

Motor Construction

            I recently performed a physics lab in which I constructed an electric motor in order to practically understand the principles of magnetism and electricity that make it work.

I found it to be actually really fun and more interesting that I first thought it would be. I chose to make just a simple motor so that I could relate the right hand rule principles and electromagnetism principles to it more easily. A 20 gauge enamel-coated copper wire was wounded around a D cell battery approximately 30 times. The wire was cut and then each free end of the wire was wrapped around the coil twice. This created the main coil of the electric motor. The ends of the wires were pulled out straight. With the coil perpendicular to the table, a razor knife was used to scrape off the enamel insulation layer on one side of the wire. This was done so that the electrical connection to the coil would be disconnected with every half rotation of the coil. Four small holes were drilled into a piece of wood. This was used to create the base structure for the coil. Pliers were used to shape the heavy gauge steel wire into a two supports for the coil. The selection of the heavy gauge steel wire gave enough flexibility to be able to readily shape the coil supports, but was still stable. In addition, the steel wire is a conductor, which is required for the current to reach the coil. The ends of the supports were stuck into the wooden board and two magnets were stacked in the middle of them. The coil was inserted into the supports and the magnets and supports had to be readjusted until the coil was centered over the magnet at an appropriate distance. Finally, the battery clip for the 9 volt battery was hooked up to the steel wire.

When the battery is attached to the steel conductor wires, the current passes flows from the positive to the negative end of the battery. The electricity goes through the coil which leads to the creation of a magnetic field around the coil wire. This creates for a magnetic field around the wire interacting with the magnetic field of the bar magnets underneath. Because of the way the two fields are oriented together, when the electricity passes through, the force pushes one end of the coil upward. When the coil turns far enough, the circuit is broken because the insulated enamel wire is contacting the metal supports, and only the momentum of the coil keeps it moving. When it turns a complete cycle, the connection is once again established, and the same repulsive force pushes the end of the coil upwards again until it is perpendicular to the magnetic field. This cycle repeats with each turn of the coil and creates a motor. The “axel” of the motor (the wires that extend from each end) thus rotate and could be used to perform some mechanical work. Using right hand rule two, I figured out that when the bare copper wire is in contact with the steel wire, the current around the coil turns in a counter clockwise direction. This means that the north pole of the magnet is coming out of the page. Looking at the direction that the wheel turns, the bottom of the coil was repelled upwards by the north end of the magnet.

There were several challenges in building the model. The specific orientation of the coil relative to the magnet was very particular for the motor to properly function. The stripping of the wire needed to be very thorough for a sufficient connection to occur. As well, the coil was not staying perfectly centered above the magnets, so I added one bead on each side of the coil to keep it in place. Finally, the 20 gauge wire used to make the coil was quite flexible and therefore easy to make a coil, but it made a fairly flimsy axel which requires period reshaping.

This is the website that I used to get the general idea of how to create a motor; it was really helpful! I strongly suggest this website to anyone who is planning to build a simple motor. http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p009.shtml.