The genetic code is the set of rules that governs the relationship between the nucleotide sequence of DNA or RNA and the amino acid sequence of proteins. The code is essentially a dictionary that specifies the correspondence between each triplet of nucleotides, called a codon, and a specific amino acid or a stop signal.
The genetic code is universal, meaning that the same codons code for the same amino acids in all organisms, from bacteria to humans. There are 64 possible codons, but only 20 amino acids and three stop signals to be coded. Therefore, multiple codons can code for the same amino acid, a property known as degeneracy or redundancy.
The process of translating nucleotide sequences into amino acid sequences involves several steps. First, the DNA sequence is transcribed into messenger RNA (mRNA), which carries the genetic information to the ribosome, the cellular machine responsible for protein synthesis. During translation, the ribosome reads the mRNA sequence in groups of three nucleotides, or codons, and matches each codon with the corresponding amino acid or stop signal.
The matching is based on the genetic code, which is read in a specific order, starting from the 5′ end of the mRNA. The first codon to be read is the start codon, AUG, which codes for the amino acid methionine and signals the ribosome to start protein synthesis. The ribosome then reads each subsequent codon and adds the corresponding amino acid to the growing protein chain until it encounters a stop codon, UAA, UAG, or UGA, which signals the end of the protein.
In summary, the genetic code is a set of rules that governs the translation of nucleotide sequences into amino acid sequences. It is based on the correspondence between each triplet of nucleotides, or codon, and a specific amino acid or stop signal. The process of translation involves reading the mRNA sequence in groups of three nucleotides and matching each codon with the corresponding amino acid or stop signal based on the genetic code.