Unit 5 Reflection

This unit was about the relation between DNA and physical traits. Some of the themes were the double helix, antiparallel shape of DNA; semi-conservative DNA replication, the process of creating two identical strands of DNA from a single one, each ending up with half of the original strand; transcription, how RNA is created in the nucleus; translation, how ribosomes read RNA to create proteins; the types of mutations: point mutations, frameshift mutations like insertion and deletion, inversion, and translocation; and how genes are regulated within an operon.



My strengths this unit were understanding semi-conservative DNA replication, transcription and translation, the different types of mutations, and the lac operon. I found these processes logical and easy to follow. My weaknesses this unit were understanding the antiparallel structure of DNA, doing transcription and translation by hand, and understanding DNA structure's influence of gene expression. I didn't understand antiparallel at first because it didn't make sense, but now I do. I struggled doing transcription and translation by hand because I am easily distracted. Originally, the topic of DNA structure and its influence on gene expression seemed very complicated, but now I realize it is pretty simple.



I would like to learn more about why DNA is shaped as it is, and why ribosomes can't just read DNA in the nucleus inside of the copied RNA. I am also curious about what would happen to the rest of the RNA if the ribosome was told to stop near the beginning of the RNA sequence. I would also like to learn about the probability for each mutation, and how efficient gene regulation truly is.

I am growing as a student by studying in a more effective way. I have begun creating flashcards and looking at more diagrams in order to study. This is an effective method to study for me because, according to the VARK Questionnaire, I have high visual, kinesthetic, and reading/writing scores. The flashcards are helpful because of my reading/writing score, while the diagrams are helpful due to my visual score. I have not yet found a way to incorporate my kinesthetic abilities into studying.

Protein Synthesis Lab Analysis

There are two main steps to make a protein: transcription and translation. In transcription, a section of DNA is copied, producing messenger RNA. In translation, the RNA reaches a ribosome. The ribosome reads bases 3 at a time. Each 3-base sequence corresponds to an amino acid, which the ribosome adds to the protein it is creating. After that, the amino acid chain folds and becomes a protein.



There were three different types of mutations we tested: substitution, insertion, and deletion. Substitution either caused a great change or a very small change. Sometimes, it caused no change at all. Substitution was only an effective mutation when it was placed in a strategic position. Insertion and deletion both caused major changes when done at the beginning of a sequence. However, towards the end of a sequence, insertion and deletion caused much smaller changes.



During this lab, I was allowed to choose a mutation of my own to test. I chose to test substitution, because after looking at the bases of the gene I was given, I realized I could easily substitute strategic nucleotides in order to get a drastically different result. I substituted two nucleotides in the beginning of the sequence, turning TAC into ATC. This changed the resulting RNA sequence from AUG to UAG. Basically, I changed the start codon to the stop codon. As you can imagine, the amino acids of the resulting protein were very much changed. Instead of the protein Met-Tyr-Lys-His-Val-Ile-Asn-Cys-Ile, there was no protein at all. This mutation changed more amino acids than any other tested. Obviously, placement did matter; if I just substituted bases at random, I would not have gotten the same result.



Mutations could affect our lives in many ways. An example of a mutation is Huntington disease. According to the U.S. National Library of Medicine's Genetic Home Reference, Huntington disease is caused by a mutation in the HTT gene, which provides instructions to make the huntingtin protein. Usually, in this gene, the sequence of cytosine, adenine, and guanine is repeated 10 to 35 times. However, within those with Huntington disease, this sequence is repeated much more, making the mutation an insertion. The length of the sequence of cytosine, adenine, and guanine creates very long huntingtin proteins, which are cut apart and bind together. This eventually causes neurons to die. Huntington disease is inherited with an autosomal dominant pattern.

DNA Extraction Lab Analysis

In this lab, we asked the question, "How can DNA be separated from cheek cells in order to study it?" We found that DNA can be separated from cheek cells by adding Gatorade, salt, detergent, pineapple juice, and isopropanol alcohol, in that order. This process is a legitimate way to extract DNA because after we completed this procedure, we were all able to see at least some bits of DNA in our test tubes. We also noticed clumps in our mixtures throughout the process, and those clumps turned out to be pieces of DNA. Each step of our procedure stems from scientific research. DNA is usually extracted through a three-step process including homogenization, lysis, and precipitation. Gatorade was added because it is a polar liquid, able to homogenize cells. Salt was added so that the DNA would move closer to itself, and detergent was added to break down the cell membranes. Pineapple juice contains catabolic proteases, enzymes that break down molecules. It was added to break down histones, which are proteins that DNA wraps around. Isopropanol alcohol is nonpolar; we layered it on top of the mixture so that the DNA would become visible as a precipitate. Our data supports our claim because if we were able to see DNA after following our procedure, then we must have extracted DNA through the procedure. The scientific ideas support our claim because each step of our procedure is supported by scientific evidence, and the end results of both are extracted DNA.

My DNA falls out as a precipitate during the last step of our process.

While our hypothesis was supported by our data, there could have been errors due to how the cheek cells were gathered. In order to gather cheek cells, we chewed at our cheeks and spit into cups. However, we were unsure how long or how much to chew at our cheeks, so we may have not chewed enough. This would explain why some people only had small pieces of DNA in their test tubes. Also, instead of mixing the cheek cells, Gatorade, salt, detergent, and pineapple juice together in a test tube, we mixed them in cups instead. This did not impact our result a lot, but it made the lab a little messier, and we were worried that the cups might start to leak. Due to these errors, in future experiments I would recommend gathering cheek cells by scratching the inside of your cheeks using a toothpick. I would also recommend telling students a few hints on the procedure if they get stuck.

This lab was done to demonstrate how to extract DNA. During this lab, we learned the three basic steps to extract DNA, and the ingredients that could be used for each of these steps. From this lab, I learned about the structure of cells and which enzymes are able to break down those structures, which helps me understand the concept of where DNA is stored in a cell and how important it is. Based on my experience from this lab, I could extract DNA from nearly anything, which would be useful if I wanted to become a geneticist. I could also compare different DNA to see if I could find any similarities or differences. Also, if I had a microscope, I could use it to look at DNA and learn more about what it looks like. I also know more vocab words due to this experiment, which will help me later in science classes.