Final answer:
The degeneracy of the genetic code means multiple codons can specify the same amino acid, aiding in buffering against mutations and contributing to genetic variance without detrimental effects. The universality of the genetic code across almost all organisms suggests a common evolutionary origin and has been highly conserved, likely due to this degeneracy.
Step-by-step explanation:
The Genetic Code and its Degeneracy and Universality
The genetic code refers to the rules by which information encoded in genetic material (DNA or mRNA sequences) is translated into proteins by living cells. The code defines how sequences of nucleotide triplets, called codons, are translated into amino acids, which are the building blocks of proteins. Each codon consists of three nucleotides and there are 64 possible codons; however, there are only 20 standard amino acids. This fact leads to degeneracy, meaning that multiple codons can specify the same amino acid.
The degeneracy of the genetic code is a buffering mechanism against mutations, as changes in the third nucleotide of a codon often do not change the encoded amino acid, thereby reducing the impact of random mutations on the protein function. This aspect of degeneracy is advantageous for the negative impact of random mutations in natural selection and evolution. It allows a certain level of genetic variance without detrimental effects on the organism, which can be a substrate for evolution.
Another key characteristic of the genetic code is its universality; with few exceptions, it is the same in almost all organisms. This universality suggests a common ancestry for all life forms and implies that the genetic code was established early in the evolutionary history. The near-universality also indicates that once the code was established, it was highly conserved throughout evolution, possibly due to the constraints imposed by the degenerate nature of the code.
To understand the universality and degeneracy of the genetic code further, we can examine the theoretical underpinning that led to these discoveries. Scientists initially hypothesized that the genetic code might be composed of nucleotide doublets, but quickly realized that the 16 combinations would not suffice to encode all amino acids. Thus, a three-nucleotide codon system was proposed and later confirmed, revealing the degenerate nature of the genetic code.