An analysis of chromosomal DNA using the southern hybridization technique does not use

Options

A. PCR
B. Electrophoresis
C. Blotting
D. Autoradiography

Explanation

**Step-by-Step Solution:**

1. **Understanding Southern Hybridization**: Southern hybridization is a technique used to analyze chromosomal DNA. It helps in identifying the presence and quantity of specific DNA sequences based on their sizes.

2. **Steps Involved in Southern Hybridization**:
- **Step 1: DNA Digestion**: The DNA sample is digested using restriction endonucleases. These enzymes cut the DNA at specific sites, resulting in fragments of varying lengths.
- **Step 2: Agarose Gel Electrophoresis**: The digested DNA fragments are separated by size using agarose gel electrophoresis. Larger fragments move slower and remain closer to the wells, while smaller fragments move faster and travel further down the gel.
- **Step 3: Blotting**: The separated DNA fragments are transferred from the gel to a nitrocellulose or nylon membrane. This process is known as blotting.
- **Step 4: Labeling**: A radioactive or fluorescent probe (like P32) is used to label the DNA fragments on the membrane. This probe will hybridize with the specific DNA sequences of interest.
- **Step 5: Hybridization and Washing**: The membrane is incubated to allow the probe to bind to its complementary DNA sequences. After hybridization, excess probes are washed away.
- **Step 6: Autoradiography**: The membrane is exposed to X-ray film, allowing for visualization of the hybridized DNA fragments. This step helps in identifying the size and presence of specific DNA sequences.

3. **Identifying the Step Not Used**: The question asks which technique is not used in Southern hybridization. The options provided include:
- Option 1: PCR (Polymerase Chain Reaction)
- Option 2: Electrophoresis
- Option 3: Blotting
- Option 4: Autoradiography

Upon reviewing the steps, it is clear that PCR is not involved in any of the steps of Southern hybridization. PCR is a technique used for amplifying DNA, which is not part of the Southern blotting process.

4. **Conclusion**: The correct answer is Option 1: PCR, as it is not used in the Southern hybridization technique.

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