The burning of fossil fuels by humans is the largest source of emissions of carbon dioxide, which is one of the greenhouse gases that allows radiative forcing and contributes to global warming.
The genetic code. Efforts to understand how proteins are encoded began after DNA's structure was discovered in 1953. George Gamow postulated that sets of three bases must be employed to encode the 20 standard amino acids used by living cells to build proteins, which would allow a maximum of 43 = 64 amino acids.
Proteins are formed from amino acid subunits. Each triplet nucleic acid, (called a codon) in a the D.N.A. molecule codes for a specific amino acid. There are about 23 different amino acids that humans use for protein synthesis. Some of the codons are redundant.