Final answer:
To determine the genetic code, scientists added mRNA to a 'cell-free' bacterial cell extract containing ribosomes and tRNAs, which allowed them to match mRNA codons with their corresponding amino acids.
Step-by-step explanation:
To determine the codons of the genetic code, scientists added mRNA and amino acids to an extract from bacterial cells containing ribosomes and tRNAs that was called cell-free system. This experimental setup allowed them to decode the relationship between specific mRNA sequences (codons) and the amino acids they specify, thereby revealing the rules of the genetic code.
The process of transcription generates mRNA which is then used in the process of translation to synthesize proteins. In this process, each three-nucleotide sequence of mRNA, a triplet codon, is matched with its corresponding amino acid. Understanding how codons direct the addition of specific amino acids was crucial for unraveling the genetic code, which is nearly universal for all life on Earth.
The genetic code consists of 64 triplet codons in mRNA that specify 20 amino acids and three stop codons, is degenerate, meaning that multiple codons can code for the same amino acid. For example, the codon GGU codes for glycine, while GUC codes for valine, showcasing the specificity of this coding system. The correct pairing of codons and amino acids is essential for the accurate synthesis of proteins within cells.