Unit 5 Reflection

In this unit, called "Walking the Dogma" we took a closer look at DNA, the genetic code that is in each and every one of our cells. In the previous unit, we learned that our DNA codes for genetic traits, but we didn't know the specifics of how it did that. DNA stands for deoxyribonucleic acid; it is a double-helix and it is composed of nucleotides. Nucleotides are composed of a 5-carbon sugar (in this case deoxyribose), a nitrogenous base (either Adenine (A), Thymine (T), Cytosine (C), or Guanine (G)), and a phosphate group. The structure of DNA resembles a ladder; the backbone is composed of a phosphate group and a sugar, and the rungs are composed of nitrogenous bases. The double-ringed bases, called purines, bond with the single-ringed bases, called pyrimidines. Adenine and Guanine are purines, while Cytosine and Guanine are pyrimidines. I felt that this part of DNA structure was definitely one of my strengths.

We also learned that DNA is antiparallel meaning that one side runs from 5' to 3' and the other side runs from 3' to 5'. The phosphate group from one nucleotide bonds with the carbon from another. I understand the basic principle of this, but I think that the details of the bonding is a weak point for me.

When we studied the cell cycle, we learned that DNA replicates itself in interphase. In semi-conservative replication, when DNA is unzipped, there are two identical strands, each half of the original. An enzyme called helicase breaks the hydrogen bonds that the nitrogenous bases have with each other. Then another enzyme called DNA Polymerase adds the matching nucleotides to each strand. I feel that I have a clear understanding of this topic. One of the main topics that we studied this unit was protein synthesis. At a 10,000 ft level, the Central Dogma of biology states that genetic information flows from DNA to RNA (transcription) to proteins (translation) to our traits. RNA has uracil instead of thymine, and is single-stranded. It is in some ways similar to a temporary copy of DNA. I felt I was able to understand this process fairly well.

The graphic illustrates the process of how DNA is copied. 

Most of the time, DNA is copied correctly and humans are given the correct proteins that they need to functions. However, sometimes mutations--changes in the DNA, can arise. One type of mutation is a substitution, when one base pair is substituted for another. At its worst, it can change one amino acid, however, sometimes it causes no change at all, resulting in a silent mutation. Another type of mutation is a frameshift mutation, either when a base pair is inserted or deleted, and it cause all the amino acids afterwards to change.

One of the topics that I initially found to be challenging but that I understand now was the ways that genes are regulated. Every cell has the same DNA, and that certain genes have to be turned on or off depending on what type of cell it is.

I have learned much more about DNA and how it is copied and how proteins are made from this unit. From the VARK Questionnaire we took last time, I learnt that I am multimodal, but visual was my highest score. I tried to redraw and memorize diagrams which helped me. Also, I feel that when I try to label unlabeled diagrams for Do Now's in class, I retain the information a lot better.