If the first three nucleotides in a six-nucleotides-recognition sequence are CTG, what would be the next three nucleotides most likely?

Options

A. AGG
B. GTC
C. CTG
D. CAG

Answer

To determine the next three nucleotides in a six-nucleotide recognition sequence when the first three nucleotides are CTG, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Palindromic Sequences**:
- Recognition sequences for restriction enzymes are often palindromic. This means that the sequence reads the same in both directions when considering complementary strands.

2. **Identify the Given Sequence**:
- The first three nucleotides provided are CTG.

3. **Determine the Complementary Sequence**:
- To find the next three nucleotides, we need to identify the complementary bases for CTG:
- C (Cytosine) pairs with G (Guanine)
- T (Thymine) pairs with A (Adenine)
- G (Guanine) pairs with C (Cytosine)
- Therefore, the complementary sequence to CTG is GAC.

4. **Construct the Full Sequence**:
- Since we are looking for a six-nucleotide sequence, we can combine the first three nucleotides (CTG) with their complementary sequence (GAC).
- Thus, the complete sequence would be CTG followed by GAC.

5. **Conclude the Next Three Nucleotides**:
- The next three nucleotides after CTG in the recognition sequence are therefore GAC.

### Final Answer:
The next three nucleotides most likely to follow CTG in the six-nucleotide recognition sequence are **GAC**.

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