Final answer:
The genetic code has one start codon and three stop codons for the initiation and termination of protein synthesis. This helps prevent errors and ensures accurate translation.
Step-by-step explanation:
The biological reasons for having only one start codon and three different stop codons in the genetic code are as follows:
Initiation of Protein Synthesis: The start codon (AUG) is necessary to initiate protein synthesis in both prokaryotes and eukaryotes. It signals the beginning of translation and the incorporation of the first amino acid (usually methionine) into the growing polypeptide chain.
Termination of Protein Synthesis: The three stop codons (UAA, UAG, and UGA) act as termination signals, indicating the end of translation. When a stop codon is reached, no further amino acids are added, and the polypeptide chain is released from the ribosome.
Preventing Ambiguity: Having only one start codon and three stop codons ensures that there is no confusion in the reading of the genetic code. Each codon codes for a specific amino acid or serves as a start/stop signal. This prevents errors in protein synthesis and ensures accurate translation.