Consider the following statements about the genetic code and identify which of them is/ are INCORRECT.
1: AUG is an initiator codon.
2: Codons in bacteria and animals usually are different.
3: All codons are triplets of amino acids and code for base pairs.
4: All codons are triplets of base pairs and code for amino acids.

Options

A. only 3
B. only 2 and 3
C. only 1 and 4
D. only 1, 2 and 3

Answer

To solve the question regarding the genetic code and identify which statements are incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: AUG is an initiator codon.**
- **Analysis:** AUG is indeed known as the start codon in the genetic code. It codes for the amino acid Methionine and is recognized as the initiator codon for protein synthesis.
- **Conclusion:** This statement is **correct**.

2. **Statement 2: Codons in bacteria and animals usually are different.**
- **Analysis:** The genetic code is largely universal across different organisms, including bacteria and animals. While there may be some minor variations in specific cases (like mitochondrial codons), the majority of codons are the same.
- **Conclusion:** This statement is **incorrect**.

3. **Statement 3: All codons are triplets of amino acids and code for base pairs.**
- **Analysis:** This statement is misleading. Codons are actually triplets of nucleotides (not amino acids) that code for specific amino acids. Therefore, this statement is incorrect in its description.
- **Conclusion:** This statement is **incorrect**.

4. **Statement 4: All codons are triplets of base pairs and code for amino acids.**
- **Analysis:** This statement is also misleading. Codons are triplets of nucleotides, not base pairs. However, they do code for amino acids. The phrasing is incorrect.
- **Conclusion:** This statement is **incorrect**.

### Summary of Findings:
- **Correct Statements:** Statement 1
- **Incorrect Statements:** Statements 2, 3, and 4

### Final Answer:
The incorrect statements are **2, 3, and 4**.