Crick's "Frozen Accident" was was "designed" from the start


Crick was a regular LSD fan

The co-discoverer of DNA Francis Crick called the genetic code a "frozen accident." This was driven by his philosophy that things are not designed rather evolved. This includes the redundant codons in the code. His lack of curiosity stunted research for decades. He applied NeoDarwinism to this codon code to presume it was a "random" accident.

This concept stood for 35 years until the discovery of codon bias. Codon bias is the phenomenon where some codons are used more frequently than others during translation of genes. 


Note GC bias in codons

This can be explained by a number of factors, including:

  • The availability of different tRNAs, which are the molecules that carry amino acids to the ribosome during translation. Some tRNAs are more abundant than others, and this can lead to a bias in the codons that are used.

  • The tendency of certain codons to be used more frequently. For example, some codons may be more efficient at translation, or they may be less likely to cause errors.

  • The evolutionary history of a gene or genome. Codons that are used more frequently in one organism may also be used more frequently in its descendants.

The existence of codon bias suggests that the genetic code is not "random" as with neo darwinism, and that some codons are more favorable than others. This contradicts the idea that the genetic code is a "frozen accident."

GC bias is the main cause of codon bias.

GC bias is the unequal distribution of guanine and cytosine nucleotides in a genome. GC-rich genomes have a higher proportion of GC nucleotides than AT-rich genomes.

Codon bias is the unequal use of synonymous codons to encode amino acids. Synonymous codons are codons that encode the same amino acid.

GC bias and codon bias are correlated because most amino acids are encoded by multiple synonymous codons that differ in GC content. For example, the amino acid alanine can be encoded by the following four synonymous codons: GCU, GCC, GCA, and GCG. All four of these codons are GC-rich, but the first two, GCU and GCC, are used more frequently than the last two, GCA and GCG.

GC bias is caused by mutational biases. Mutations that change a nucleotide from an A or T to a G or C are more common than mutations that change a nucleotide from a G or C to an A or T. This is because GC base pairs are more stable (3 h-bonds) than AT base pairs (2 h-bonds).

The relationship between GC bias and codon bias is complex and varies between species. However, it is clear that GC bias is the main cause of codon bias in most organisms.

Codon bias can have a number of important effects on gene expression and protein function. For example, codon bias can affect the rate of translation, the folding of proteins, and the stability of mRNA transcripts. Codon bias is also thought to play a role in the evolution of new genes and the development of genetic diseases.

It is important to note that GC bias is a natural phenomenon. Here are some examples of how natural design cellular mechanisms can introduce GC bias into DNA:

  • DNA replication: DNA polymerase is more efficient at replicating GC-rich DNA. This is because GC base pairs (3 hydrogen bonds) more stable than AT base pairs (2 hydrogen bonds).

  • DNA repair: Certain DNA repair mechanisms, such as base excision repair and mismatch repair, can also introduce GC bias into DNA. This is because these mechanisms are more likely to repair GC base pairs than AT base pairs.

  • NonDarwinian Epigenetic modifications: Certain epigenetic modifications, such as DNA methylation and histone modification, can also affect GC content. For example, DNA methylation is associated with a decrease in GC content.

It's clear the genetic code is not a "frozen accident" rather was designed from the beginning.

So Crick's quote:

 "Biologists must “constantly keep in mind that what they see was not designed, but rather evolved."

Is replaced by:

 "Biologists must “constantly keep in mind that what they see was not a NeoDarwinian "frozen accident", rather was designed from the start."

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