The amino acid coded by the start codon for protein synthesis is :

Question

Accepted Answer

The amino acid coded by the start codon for protein synthesis is Methionine, which is Option 1. Here's a detailed explanation supporting this:

1. **Explanation for Option 1 (Methionine):**
   - In the genetic code, the start codon is AUG. This codon is universally recognized as the initiation signal for protein synthesis in eukaryotic and prokaryotic organisms. The AUG codon specifically codes for the amino acid Methionine. During the initiation of translation, the ribosome assembles at the start codon, and Methionine is incorporated as the first amino acid in the nascent polypeptide chain. This is a critical step in the process of translating mRNA into a functional protein.

2. **Explanation for why other options are incorrect:**
   - **Option 2 (Tryptophan):** Tryptophan is coded by the codon UGG, not AUG. It is not involved in the initiation of protein synthesis, and there is no start codon that codes for Tryptophan.
   - **Option 3 (Valine):** Valine is coded by the codons GUU, GUC, GUA, and GUG. None of these codons serve as a start codon, and therefore, Valine is not the amino acid incorporated at the beginning of protein synthesis.
   - **Option 4 (Arginine):** Arginine is coded by several codons, including CGU, CGC, CGA, CGG, AGA, and AGG. Similar to Valine and Tryptophan, none of these codons function as a start codon, and Arginine is not the initial amino acid in protein synthesis.

In conclusion, Methionine is the amino acid coded by the start codon AUG, making Option 1 the correct answer. This is a fundamental aspect of molecular biology and is consistent across different organisms, underscoring the universality of the genetic code.