Life Ascending ~ Week 3: The Building Blocks of Life

DNA is often called “the building blocks of life.”  However, have you ever wondered what served as the building blocks for DNA itself?  In this chapter Lane delves into the origin of DNA and RNA and discusses how they have evolved over time.  As I mentioned in my previous post, Lane believes that the hydrothermal vents served as the site for the origin of life because of the superheated environments, charged minerals and gases, and alkaline conditions that allowed for organic matter to be created.  Similarly, Lane also states that these hydrothermal vent sites serve as the location for DNA and RNA creation.   The hydrothermal vents contain pores in which thermal gradients with current pass through.  These thermal currents gradually buildup up pores with small molecules, such as nucleotides, in high concentrations.  When this happens, the nucleotides condense to form RNA or DNA chains.   The high concentration level of nucleotides that then become chains then foster the high concentration of RNA chains that exist…forcing these chains to physically interact with one another.  While the RNA chains are interacting with one another the oscillating temperatures of the thermal vents promote RNA replication…just like in PCR!  Eventually, RNA was able to evolve and learn how to replicate itself using energy.  I find this explanation of the origin of genes and the genome in the hydrothermal vents to be fascinating. 

This chapter also discusses the work that went into discovering what DNA actually coded for.  After many years of hard work scientists were able to conclude that DNA coded for a sequence of codons that make up the structure of proteins.  How did these triplet codes come to be?  It was discovered once again that these codons are originated from the hydrothermal vents in which amino acids precursors formed due to the Krebs cycle.  Therefore, the first letter of the codon sequence derived from these precursors.  The second letter of the codon sequence evolved with the association of the amino acid’s ability to dissolve in water.   Whether a codon sequence is hydrophilic or hydrophobic is determined by the identity of the second codon.  For the third codon, it was determined that it most likely evolved by natural selection to optimize the code overall.  Learning about the evolution of the codon sequence was very interesting because we use codon sequences in lab to determine the evolution of entire organisms.  We constantly manipulate DNA and codon sequences to determine how organisms have evolved over time but I have never specifically looked into the evolution of the “building blocks” themselves.  Although I found this chapter to be very interesting and insightful I wonder if there are other hypotheses that exist to explain about how the origin of these building blocks came to be.  I find that Lane consistently uses the hypothesis of hydrothermal vents but rarely mentions any other possible explanations.  Is there perhaps another way to explain how DNA and codon sequences evolved?