Genetic Code Foundation
The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins. It is universal among organisms, highlighting the shared common origin of life on Earth.
Triplet Codon System
A codon is a sequence of three nucleotides that corresponds to a specific amino acid or stop signal during protein synthesis. There are 64 different codons coding for 20 amino acids and stop signals.
Start and Stop Signals
The start codon AUG not only codes for the amino acid methionine but also signals the beginning of protein synthesis. Stop codons (UAA, UAG, UGA) do not code for any amino acid and terminate translation.
Redundancy and Wobble
The genetic code is redundant, meaning multiple codons can code for a single amino acid. The 'wobble' position, the third base in a codon, often tolerates mutations without altering the amino acid sequence of a protein.
Codon Bias Phenomenon
Different organisms preferentially use certain codons over others to code for an amino acid, a phenomenon known as codon bias. This can affect gene expression levels and is exploited in gene engineering for protein production.
Genetic Code Evolution
The genetic code is not immutable. Mitochondria, for instance, have a slightly different genetic code. This suggests that the code has evolved and adapted over time, allowing for exceptions to its universality.
Synthetic Genetic Codes
Scientists have expanded the genetic code artificially, creating organisms that can incorporate non-natural amino acids into proteins. This paves the way for novel biomaterials and therapeutic agents with unprecedented functions.
What depicts genetic code universality?
Variation across all life forms
Same code in specific organisms
Shared code among diverse organisms
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