These chapters were full of rather interesting information. One aspect of the DNA chapter that I appreciated was the discussion of the theories of how the amino acid code arose. In all the textbooks I have ever read we are simply provided with the nucleotides that make up codons not with the theories of how the codons could have evolved or what constraints would have led to the arrival of the universal code. One aspect of this chapter that broadened and extended topics we have covered in class such as PCR and the genetics of retroviruses. PCR serves as an excellent parallel for the initial of evolution of DNA and RNA. Lane states that nucleotides could build up in mineral cells formed in the deep sea vents he mentioned in chapter one. This build up of nucleotides combined with temperature gradients served as a natural PCR reaction allowing the RNA and DNA polymers to denature and extend and anneal. Looking back to the beginning of the semester Lane states that these mineral cells and nascent RNA molecules could "live" in a similar manner to retroviruses such as HIV that we studied in class. Here RNA serves as the original information carrying molecule and the development of a reverse transcriptase parallel serves convert RNA into DNA thus making the original DNA molecules. One of the really fascinating things that we did not spend a huge amount of time in class over, but I think is really informative is the point that Lane brings up about how DNA replication has evolved twice of the history of life. Once for bacteria and again in a different manner in archea.
The next chapter on photosynthesis was also very interesting as Lane describes the development of the photosynthetic system. After a monologue cataloging the awesomeness of oxygen (which I think was really cool) Lane describes the basics of the photosynthetic complex including photosystems 1 and 2 as well as a brief description of the electron transport chain and sources of electrons and energy. One way that this chapter tied into our evolution class is that it serves as an extended example of how mutations especially larger ones such as gene duplication can lead to drastic evolution. Here Lane states that photosystem 1 evolved as a method of ripping electrons from hydrogen sulphide to produce more complex organic molecules. duplication of the genes coding for this complex led to the creation of photosystem 2 and this resulted in a photosystem specialized to create ATP from dropping high energy electrons down an electron transport chain. The idea that an event that changed the history of the world so drastically as the development of photosynthesis could be distilled to a single concept we covered in class such as gene duplication is pretty awesome. The question I have is how did DNA and RNA regulate transcription without the nuclear barrier in the mineral cells? Was early DNA a free for all when it came to transcription with no regulatory regions or transcription factors?
Hey Logan, I agree with your last question. I am confused as to exactly how DNA and RNA transcription occurred when it first evolved. I feel life for such a complex process to occur transcription factors and regulatory factors are a necessity. In regards to your question you posted on my blog...I do agree that the third codon happened randomly at first. However, from my interpretation of the reading I thought the codon happened randomly and then over time became a favorable trait. Once it became a favorable trait it was selected for through natural selection.
ReplyDelete