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I can't help but notice the irony in your comment. So this guy comes along and having read one article, says "I can't call this good science." A very basic sum
by ken_e 11y ago
I can't help but notice the irony in your comment. So this guy comes along and having read one article, says "I can't call this good science."
A very basic summary of molecular biology of the cell:
DNA - library of blueprints, basically instructions on how to build proteins
RNA - copies of blueprints you take out of the library to build proteins so you don't expose DNA to unnecessary hazards
protein - catalyzes reactions so the cell can do stuff, including make new DNA when replicating.
A fundamental conundrum exists when it comes to evolution of this mechanism. DNA is needed to build proteins, but proteins are needed to catalyze the reactions necessary to build DNA. It's a chicken and egg problem... what came first?
When it was discovered that RNA can catalyze certain reactions, presumably because of their slightly higher chemical reactivity, it suggested a way out of this conundrum. What if life originated with RNA only, where RNA acted as both the hereditary and catalyzing machinery?
The problem with this RNA World hypothesis is that the reactions that current RNA can catalyze is very limited. But what if, at the origin of life, when nature could experiment, the genetic alphabet that RNA could play with was bigger, potentially leading to expanded capability? Scientists like Benner have worked for three decades to try to answer this question.
So, your characterization of "comes along, casually expand" a well-established code and claims it's better is grossly unfair.
- veddox 11y agoI am well aware of the basic molecular biology of the cell, as well as the RNA world hypothesis. All due respect to Benner for his work - my comment was rather too pointed, I'll concede that. Nonetheless, I am always wary of too much theory being induced from too little data. Benner's experiment shows that an expanded genetic code can form molecules that show greater chemical functionality in a given situation than that of natural DNA molecules. Now a quote from the abstract: > This suggests that this system explored much of the sequence space available to this genetic system and that GACTZP libraries are richer reservoirs of functionality than standard libraries. Already he is starting to extrapolate when he starts talking about the extended libraries in general. The Quantamagazine article then goes on to say: > In other words, the new additions appear to improve the alphabet, at least under these conditions. That is true, but for a rather narrow definition of "improve", and a very narrow set of conditions. The result is that the superficial reader goes away thinking "they've made a better DNA".
- gus_massa 11y ago> The problem with this RNA World hypothesis is that the reactions that current RNA can catalyze is very limited. But what if, at the origin of life, when nature could experiment, the genetic alphabet that RNA could play with was bigger, potentially leading to expanded capability? Transfer RNA currently have a few additional bases, probably to do same things that are impossible/difficult with the standard 4 bases. See: https://en.wikipedia.org/wiki/Transfer_RNA#Structure https://en.wikipedia.org/wiki/Transfer_RNA#Structure