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Originally posted by Atzil321
This is a bit technical, not sure what sort of feedback you expect here to be honest. Maybe you should post on a specialist scientific website with this kind of thing, or dumb it down to some points/questions that a layman can understand and resond to.....
Originally posted by Astyanax
reply to post by Atzil321
I think rhinoceros is saying that the genetic code shows considerable redundancy, and also seems to have evolved to work with pre-existing, abiogenetically produced amino acids. In other words, that it shows signs of being itself a product of natural selection; an intelligently designed code would be more elegant and all of a piece.
Well, at least that's what I got out of it. Open to correction.
Originally posted by squiz
Hi Rhino, glad I could inspire a thread.
It's a good question. The answer is actually already in the literature, the synonymous codons may actually affect the timing of translation and in turn affect protein folding in subtle ways and then effect what chemical tags get attatched post translation.
The problem is, that it just can't be dumbed down more. Even now many crucial parts are missing. For example, I did not even get started with initiation of translation, which is completely different in bacteria and eukarya, i.e. eukaryotic mRNAs must be capped from their 5'-ends...
I understand my posts are meaningless for our resident creationists who really don't care about the truth. Blissful ignorance and all that.
Originally posted by rhinoceros
Originally posted by Astyanax
reply to post by Atzil321
I think rhinoceros is saying that the genetic code shows considerable redundancy, and also seems to have evolved to work with pre-existing, abiogenetically produced amino acids. In other words, that it shows signs of being itself a product of natural selection; an intelligently designed code would be more elegant and all of a piece.
Well, at least that's what I got out of it. Open to correction.
That captures the essence of it rather well.
Originally posted by ImaFungi
Originally posted by rhinoceros
Originally posted by Astyanax
reply to post by Atzil321
I think rhinoceros is saying that the genetic code shows considerable redundancy, and also seems to have evolved to work with pre-existing, abiogenetically produced amino acids. In other words, that it shows signs of being itself a product of natural selection; an intelligently designed code would be more elegant and all of a piece.
Well, at least that's what I got out of it. Open to correction.
That captures the essence of it rather well.
so instead of ID you believe in SD ( stupid design)?
What We Actually Observe in Nature
We observe microevolution both in nature and through purposeful domestication within species. We do not observe macroevolution. Purposeful domestication (selective breeding) has been used to produce changes or desired variations within many species for more than 2000 years. Examples include cats, dogs, beef and milk cattle, race and plow horses, roses, wheat and corn. All have been changed through microevolution which follows Mendel’s law of inheritance, not the concept of blending traits envisioned by Darwin. Scientists admit macroevolution cannot be observed under natural conditions. If it happened, it occurred in the distant past and would be too slow to observe now.
However, in laboratory experiments, fruit flies have been altered to grow legs from there heads, one of many freakish major mutations possible. These changes were produced by large doses of radiation to greatly increase the mutation rate and alter genes. These changes neither created a new structure (just altering existed ones) nor changing the fly into a new kind of insect. These flies may breed under laboratory conditions, but cannot survive in nature because of this harmful mutation.
Davis writes, “Mutation does not introduce new levels of complexity, and it cannot be shown that it is a step in the right direction. Most observed mutations are harmful, and there is no experimental evidence to show that a new animal organism or even a novel structural feature has ever been produced from the raw material produced by mutations.
Mendel’s laws of genetics
According to Mendel’s first law (the law of segregation), in each generation, two alleles of any gene present in the parent individual segregate into independent sex cells (e.g. into individual sperm) without undergoing any change and without affecting one another. The second law (the law of independent assortment of characters) states that the individual pairs of alleles of various genes segregate into sex cells independently of one another and that the manner of segregation of one pair of alleles in no way affects the segregation of another pair. In the first decades of the 20th century, geneticists demonstrated that Mendel’s second law applies only to pairs of genes, each of which belongs to a different chromosome
Could you explain why 6 codons for Argine, and only 1 or 2 for Tryptophan causes one to infer no design?
Originally posted by rhinoceros
It's difficult to avoid seeing terms like the "DNA code" being used in this forum. To me at least, this term would imply code similar to a computer program, with recursive algorithms and such. However, in real life, no such term exists. The correct term is the "genetic code", which is simply a collection of translation tables with minor differences. According to each translation table, a triplet of nucleotides (all together 64 unique ones), read from the messenger RNA molecule by the ribosomes, define either an amino acid that is to be added to the growing polypeptide, or signal termination of translation. Below is the "universal" translation table:
As we see, the code is not random. As an example, all the four codons that begin with CC, define the amino acid Proline. As such, these codons are called synonymous. Be it CCU, CCC, CCA, or CCG, in the messenger RNA molecule, the bit of information is always interpreted similarly, that is, a Proline is added to the growing polypeptide. As we see, all together, in the universal genetic code, 8 blocks of codons are 4-fold degenerate (Leu, Val, Ser, Pro, Thr, Ala, Arg and Gly). The rest of the sixteen 4-fold codon blocks are split between two or more alternatives. As an example, the amino acid Leucine is defined by CUU, CUC, CUA, CUG, and by UUA and UUG. The other two UU codons, that is, UUU and UUC, specify the amino acid Phenylalanine. So in total, 6 different codons specify Leucine, but only two codons specify Phenylalanine. Here I would also like to note, that with the exception of the AUN and UGN codon blocks, the split codon blocks are always split so that U and C ending codons define one amino acid, and G and A ending codons another. The chemical rationale for this is, that U and C are pyrimidines, and A and G are purines. Purines and pyrimidines have different kinds of carbon rings. To keep things simple, I just note that purines have two fused rings, whereas pyrimidines have a single ring, i.e. purines are much larger than pyrimidines.
There are 10 pre-biotic amino acids. That is, no biological pathways are needed to generate them, instead in experiments such as that of Miller, these amino acids can come to be through strictly abiotic chemical reactions. Interestingly, 8 of these 10 amino acids are specified by the 4-fold degenerate codon blocks (Leu, Val, Ser, Pro, Thr, Ala, Arg and Gly). The additional two pre-biotic amino acids share the GAN codon block, and are Aspartic acid (GAU, GAC) and Glutamic acid (GAA, GAG). All the other amino acids need to be synthesized by biological pathways which involve proteins. In this context, it appears that these amino acids were added to the genetic code only after pathways for their generation were in place. For example, many amino acids are byproducts of metabolic pathways, and prior to them being added to the code, they might have represented waste products, much like how alcohol is a waste product of fermentation.
In this context, the observation that 6 codons still define 3 amino acids (Arg, Leu, and Ser), makes sense. We can extrapolate, that for example the now split UUN codon block was reserved for Leucine entirely. That is, 8 codons in total, UUU, UUC, UUA, UUG, CUU, CUC, CUA, and CUA, all represented Leucine in the primordial genetic code. Likewise, e.g. UAN and UGN codons all signaled termination of translation. In the context of the evolving code, the present day distribution of codons makes sense. However, some people insist that genetic code was designed. Would it not be fair then for these people to explain, why exactly does the present day code for example have 6 codons for Argine, but only one or two for Tryptophan, depending which genetic code we infer (e.g. in human nuclear DNA UGA signals stop, but in many mitochondria, UGA encodes Tryptophan)?
I hope we can keep the discussion civil, and provide references for the claims made.
For reference and further information:
arxiv.org...
www.sciencedirect.com...
Originally posted by addygrace
Could you explain why 6 codons for Argine, and only 1 or 2 for Tryptophan causes one to infer no design?