This chapter talked about a greatly interesting topic: DNA. It covered all the aspects of it from further elaborating on how it came about, to mutations, base pairs, amino acids and the study of all this. Although, all interesting; I found three parts to call my attention the most, because they were the sections which I knew a little about but further elaborated on what I already knew. These three parts are his discussion about DNA similarities, and the amino acids.
When Lane talks about DNA sequencing he said one quote that stood out to me, "the idea that we are 'half banana' because we share 5o percent of our genome sequence with a banana is misleading, to put it mildly. By the same reason, any randomly generated stretch of DNA would be a quarter human." The reason this resonated with me was because the one interesting fact, that sort of freak all new biology students is learning that our DNA is 50% like that of banana's, and I remember learning that and being slightly weirded out. However, after reading this section I now understand why it is, and how it actually makes sense for us to be so related to them. Lane explain this by saying that in any random stretch of DNA synthesized in the lab must be 25% similar to one of our genes chosen at random. This is because we have four different letters in the DNA alphabet, so for the DNA to match up it will happen at least 25% of the time - meaning at least one letter out every four.
When Lane talks about amino acid sequences, he related back to what is talked about in Chapter one about the primordial soup. He describes the way we discovered how nucleotides combinations code for each amino acid. Since each amino acid is made up of three nucleotides, each was determined a different way. He says the first was one that is formed in the hydrothermal vents, through simple carbon hydroxide and hydrogen bonding. The second is determined by its degree to which an amino acid is soluble or insoluble in water - its hydrophobicity. The last he talk about as the fourfold degeneracy, which means that the third codon is information free; it at times be interchanged with other codons and not affect the amino acid coding. I found this incredibly interesting! I had never learnt of this in any biology class so just reading it felt great to now how we came up with the alphabet for the different amino acid codes.Lastly, one quote that wen reading I had to stop and write down is the following. It shows exactly how DNA is the basis of life and the basis of evolution. "DNA, of course, is the stuff of genes, the hereditary material. It codes for human being and amoeba, mushroom and bacterium, everything on this earth bar a few viruses. Its double helix is a scientific icon, the two helices pursuing each other round and round in an endless chase."
Hey Philip! I found the evolution of codon sequences to be very interesting as well. However, I am curious about the last codon...why do you think a third codon was added if serves no purpose? This really sparked my interest when I was reading this chapter.
ReplyDeleteCelina, changing the third position often doesn't change the amino acid - but sometimes it does!! With only two positions of a codon, you can only code for 16 amino acids, but there are 20, so the third position sometimes matters a lot.
ReplyDelete