Unit 5 Reflection

This unit was about our genetic code, how it replicates, how it is used to make proteins, errors that can occur, and how organisms control how traits are expressed. Our DNA is unique because it is wound up in a tight double helix. When it replicates, it unzips, and complementary bases join to form 2 strands of the DNA. DNA is made of A, T, C, and G. However, when it replicates, errors, or mutations can occur. While some may be as simple as a substitution, others, like insertion and deletion can completely change the protein that is being coded for and possibly be fatal. DNA contains instructions for the cell to make proteins. This process of making proteins based on DNA happens in multiple steps. First, DNA is transcribed into mRNA, adding the complementary bases, but with uracil instead of thymine, and is also single stranded. Then, the mRNA travels to the ribosome, where it is translated into amino acids by every 3 bases (codons). The amino acids form a chain, which twists and folds to form proteins. The final main idea from this unit is that although every cell contains the genetic code for all proteins, only certain genes are actually expressed. This is called regulation, so that the cell doesn't waste energy making all of these proteins it doesn't even need. For example, there is the lac operon. The DNA is transcribed based on the repressor, and whether it fits on the operon. Also, in order for DNA to fit into such tight spaces, it is wrapped around proteins called histones, forming nucleosomes. This is what makes up the chromosomes.

I mostly struggled with gene expression and regulation, because it was a new idea. The lac operon was a bit confusing at first too. I enjoyed learning about actually walking the dogma. I learned a lot more about the connection between what a cell does, and how it knows to do that. I also enjoyed looking up random, weird mutations that people have and learning about what causes them (see my previous blog post for a video of a family that walks on all fours and behaves like prehistoric hominids). I think I am getting better at not getting discouraged when I don't get something in a vodcast. Now, I am more confident, and even if I don't get it the first time, I know I will understand after recapping and some studying.


I want to learn more about stem cells. I think its very interesting that they can morph into different kinds of cells. I also want to learn more about tumors and cancers, and how they can be caused. Lastly, I want to learn about expression and regulation in humans. 

Protein Synthesis Lab Conclusion

Proteins are made in different steps that occur in different places in the cell. First, in the nucleus, DNA is transcripted into mRNA by the enzyme, RNA Polymerase. Then the mRNA is transported through the cytoplasm, to the ribosome. Then, each codon, or set of 3 bases, is translated into protein language, or amino acids. Amino acids join to form a chain, called a polypeptide. The chain then bends, folds, and twists, eventually forming a protein.

Based on the results, substitution made the least difference, but frameshift mutations like insertion and deletion made the most flawed proteins. When a substitution happens, there is still a chance that the same amino acid will form, or there will just be one small error. But insertion and deletions towards the beginning of the sequence, completely changed the rest, starting from the mutation, onwards.

The mutation that had the absolute greatest effect was insertion or deletion of one of the first 3 bases of the sequence. This meant that the first amino acid, "MET", was altered, therefore there was no start codon. This means that there would be no protein because the translation never even started! This type of insertion that happened at the beginning affected the protein the most.

Many mutations could be in my genes, yet I don't even know it. Because some of them have little to no effect, but others can be fatal, you never know what mutations might exist in you. An example of a disease caused by a mutation is Uner Tan Syndrome. People with this disorder walk on all fours and behave like apes. Its like going backwards through evolution almost! Below is a documentary featured on BBC2 in 2006  about a Turkish family with this disorder, called "The Family that Walks on All Fours."

Unit 4 Reflection

One of the labs we recently did was the "Coin Sex Lab". In this lab, we simulated sex by flipping coins with different alleles on each side, to see what traits our 'children' would have. Coins serve as a model for genetics because traits are random, and the side that a coin will land on is random as well. In the dihybrid cross, we expected 9 kids to have brown hair and brown eyes, 3 to have brown and blue, 3 to have blonde and brown, and 1 to have blonde and blue. Our results were very similar to our prediction as the numbers, respectively, were 10, 3, 1, and 2. This is based on chance and probability. We can use probability to see how likely our offspring will be to get certain traits, but can't predict exactly. This relates to my life because now I understand how I could've gotten my traits.

In this unit, we learned about the topic of Why Sex Is So Great. We learned about the Cell Cycle and Mitosis Vs. Meiosis. Mitosis had one divisions, and went from diploid to diploid, while meiosis had 2 divisions and went from 2n to n. We also learned about Gregor Mendel's experiments with pea plants and how he came to realize certain traits dominated over others. Traits come in different versions, called alleles. Mendel came up with 2 laws, the Law Of Segregation, and the Law Of Independent Assortment. The Law of Segregation stated that chromatids split apart during meiosis. Independent Assortment meant that genes assorted randomly. There are also complications to genetics, such as codominance, where 2 traits both show up fully, incomplete dominance where neither trait completely dominates over the other, and epistasis, and polygenism. We also learned how to do crosses such as monohybrid and dihybrid crosses.

The basic genetics were easy for me and made sense. I remembered dominant and recessive from seventh grade, and Punnett Squares, but crosses were a bit confusing. Dihybrid crosses took some practice to get the hang of, but eventually, it became easy. The infographic also helped me organize what I learned in the unit, and I knew what information was most important to know, because if it was super important, I'd include it there. I want to learn more about polygenic traits and epistasis, generally the genetic exceptions. They seemed really interesting to me. Overall, this unit helped me understand about myself, how I could've gotten my traits, and I am now curious about traits more.

DNA Extraction Lab Conclusion

In this lab we asked the question,"How can DNA be separated from cheek cells in order to study it?" We found that by homogenization, lysis, and precipitation, DNA can be distracted. After carrying out these processes and adding alcohol, DNA formed as a precipitate on the test tubes and was visible to the naked eye. This worked because homogenization mixed the DNA and Gatorade, and lysis destroyed the membranes protecting the DNA. Finally, the alcohol being non polar, caused the DNA to form as a precipitate on the tube. This data supports our claim because the precipitate formed, so the DNA was extracted.

While our hypothesis was supported by our data, there could have been errors due to adding too much Gatorade (there was no exact measurement), or too much of any ingredient, diluting the solution. Another error that could've occurred was when pouring the alcohol. If you poured it in all at once, it would mix with the solution and not allow DNA to form. Due to these errors, in future experiments, I would recommend providing exact measurements on the instruction sheet for the lab, and pouring the alcohol slower and from the side.

This lab was done to demonstrate that DNA can be distracted, and which scientific principles are used in the process. From this lab, I learned about homogenization, lysis, and precipitation. This helped me understand the concept of polarity, and membranes in the cell. Based on my experience from this lab, I know how to extract DNA, so I would try to modify the experiment by using different ingredients to get the same result. For example, water instead of Gatorade, and papaya juice instead of pineapple juice, different types of soap, etc.