This method of finding a gene is used when researchers know very little about the gene they are trying to find. This process results in a complete gene library: a collection of copies of DNA fragments that represent the entire genome of an organism:

Options

A. Cloning
B. Shotgun cloning
C. Gene synthesis cloning
D. PCR

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a method used to find a gene when researchers have limited knowledge about it. The method should result in a complete gene library that represents the entire genome of an organism.

2. **Identifying the Method**: The method that fits this description is known as **shotgun cloning**. This technique is used when researchers want to analyze the genome without prior knowledge of the specific genes they are targeting.

3. **Process of Shotgun Cloning**:
- **DNA Fragmentation**: The first step in shotgun cloning involves treating the DNA with **restriction endonucleases**. These enzymes act as molecular scissors, cutting the DNA into smaller fragments.
- **Cloning of Fragments**: Once the DNA is fragmented, these pieces are then cloned. This means that the fragments are duplicated to create multiple copies.
- **Formation of Gene Library**: The result of this process is a **complete gene library**, which is a collection of DNA fragments that together represent the entire genome of the organism.

4. **Exclusion of Other Options**:
- **Cloning**: This term refers to creating a genetically identical copy of an organism, which is not what is described in the question.
- **Gene Synthesis Cloning**: This method involves synthesizing a gene from known sequences, which does not apply here since the question specifies limited knowledge about the gene.

5. **Conclusion**: Therefore, the correct answer to the question is **shotgun cloning**.

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