Sometimes the starting codon is GUG in place of AUG. GUG normally stands for

Options

A. Valine
B. Glyycine
C. Methionine
D. Tyrosine

Answer

To solve the question about what GUG normally stands for, we can follow these steps:

### Step 1: Understand the Role of Codons
Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids. The starting codon is crucial for initiating protein synthesis.

**Hint:** Remember that codons are made up of three nucleotides and each codon corresponds to an amino acid.

### Step 2: Identify the Common Starting Codon
The most common starting codon in eukaryotes is AUG, which codes for the amino acid Methionine.

**Hint:** Think about the significance of the AUG codon in the context of protein synthesis.

### Step 3: Explore the Role of GUG
In prokaryotes, such as Escherichia coli, GUG can also function as a starting codon. This indicates that GUG has a role in initiating protein synthesis in certain organisms.

**Hint:** Consider the differences between eukaryotic and prokaryotic translation processes.

### Step 4: Determine What GUG Codes For
GUG codes for the amino acid Valine. Valine is one of the 20 standard amino acids and has several codons, including GUU, GUC, GUG, and GUA.

**Hint:** Recall that amino acids can be coded by multiple codons, and identify Valine's structure or properties.

### Step 5: Conclusion
Thus, GUG normally stands for Valine in the context of protein synthesis.

**Final Answer:** GUG normally stands for Valine.

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