The book I'm reading at the moment, Genome by Matt Ridley, is a great work of popular science, but it also got me thinking about an often overlooked molecule, RNA. A Biologist like myself would never overlook such a vital molecule, but most people assume DNA is the one man team of our cells, controlling their every action much akin to how a queen bee controls her infertile triploid workers. However, this could not be further from the truth. In our cells, you've got your mRNA copied from the antisense DNA strand in transcription, which carries the vital codons needed to build proteins in translation, you've also got tRNA, which collects amino acids from the cytoplasm and brings them to the ribosome surface for translation, you've got rRNA, a vital subunit in the production of the manufacturing bases of cells; the ribosomes, and then there's miRNA involved in epigenetic chromosome modifications, snRNA for splicing out introns and it can even act as a CATALYST, for itself (mind=blown). I mean, it even created DNA by mutation during the early days of life on earth. I hope you now see the importance of RNA. I may have gone a little over the top there...
Anyway, getting back to Genome. In the book RNA is described as 'an unstable substance', which it most definitely is; it cannot withstand extremes of temperature or pH, which leads me onto my next point about the Last Universal Common Ancestor (affectionately refereed to as LUCA) and bacteria. Now, some scientists buy into the theory that we are the product of bacteria-like organisms ingesting each other through endocystosis, and stealing the genes of other organisms-we are the product of the evolution of many different lines of organisms, a community. It just makes you feel so warm and fuzzy inside, until you read the all together less holistic rival theory. It states that bacteria came way later than our LUCA, and the theory is based on, you didn't guess it, RNA. You see, bacteria dropped the primitive molecular RNA remnants of the their evolution from LUCAs to live in warmer climates, where the RNA would rapidly decompose. This way they could focus on speed of reproduction and out-competing other organisms instead of developing complexity, which may have led to mutations in the temperatures of around 170 degrees Celsius reached in the underground geothermal vents. Our ancestors, eukaryotic protozoa, were polyploid and had genetic material arranged into several linear chromosomes, and kept the unnecessary RNA, as their USP was their complexity. In summary, bacteria are more 'highly evolved' than we are! Thanks for the nightmares biology...
