Organisms of all three domains of life usually use the mRNA codon AUG as the start codon.

Do organisms of the three domains use the same amino acid as the initial amino acid in translation? Identify similarities and differences.

Verified step by step guidance

1. span>1. Understand the role of the start codon AUG in translation: The start codon AUG is universally recognized as the initiation signal for protein synthesis in all three domains of life: Bacteria, Archaea, and Eukarya.</span
2. span>2. Recognize the amino acid encoded by AUG: In all three domains, the AUG codon typically codes for the amino acid methionine (Met) in eukaryotes and archaea, and a modified form of methionine, N-formylmethionine (fMet), in bacteria.</span
3. span>3. Compare the initiation process across domains: In eukaryotes and archaea, the initiator tRNA carries methionine, while in bacteria, the initiator tRNA carries N-formylmethionine, which is later removed during protein maturation.</span
4. span>4. Identify similarities: All three domains use AUG as the start codon and methionine as the initial amino acid, highlighting a conserved mechanism in the initiation of translation.</span
5. span>5. Identify differences: The primary difference lies in the form of methionine used; bacteria use N-formylmethionine, whereas eukaryotes and archaea use methionine without the formyl group.</span

Key Concepts

Start Codon

The start codon, AUG, is a specific sequence in mRNA that signals the beginning of translation. It codes for the amino acid methionine in eukaryotes and archaea, while in bacteria, it can also code for a modified form called N-formylmethionine. Understanding the role of the start codon is crucial for grasping how protein synthesis initiates across different organisms.

Translation Initiation

Translation initiation is the first step in protein synthesis, where the ribosome assembles around the mRNA. This process involves the recognition of the start codon and the recruitment of the initial tRNA carrying the corresponding amino acid. The mechanisms of initiation can vary among the three domains of life, affecting the initial amino acid incorporated into the growing polypeptide chain.

Amino Acid Variability

While AUG universally codes for methionine in eukaryotes and archaea, bacteria utilize it to code for N-formylmethionine. This distinction highlights a key difference in translation initiation among the three domains of life. Understanding these variations is essential for comparing the molecular biology of different organisms and their evolutionary relationships.