Detecting Viral Insertions in the Genome: The Role of Southern Blotting

The virus inserted in genome can be recognized by
A. FISH
B. Northern blot
C. Microarray
D. Southern blot

Which Technique Detects a Virus Inserted into the Genome?

When a virus integrates its DNA into a host genome, detecting its presence is crucial for understanding viral infections, gene therapy, and disease progression. The correct answer is:

✅ D. Southern Blot

Southern blotting is a DNA hybridization technique used to detect specific DNA sequences, including viral DNA integrated into the host genome.

How Does Southern Blotting Detect Viral Insertions?

1. Genomic DNA Extraction:

   • The host cell’s DNA is isolated from the tissue or cultured cells.

2. Digestion with Restriction Enzymes:

   • DNA is cut into fragments using restriction enzymes to analyze specific sequences.

3. Agarose Gel Electrophoresis:

   • The DNA fragments are separated based on size through gel electrophoresis.

4. Denaturation:

   • The double-stranded DNA is denatured into single strands using an alkaline solution (NaOH).

5. Transfer to a Nitrocellulose or Nylon Membrane:

   • The DNA is transferred onto a solid membrane via capillary or vacuum transfer.

6. Hybridization with a Labeled Probe:

   • A radioactive or fluorescently labeled DNA probe complementary to the viral DNA sequence is applied.

7. Detection:

   • The hybridized probe reveals the presence and location of viral DNA in the genome.

Why Are the Other Options Incorrect?

❌ A. FISH (Fluorescence In Situ Hybridization)

• Detects chromosomal abnormalities and large genetic insertions, but is less effective for viral integration analysis.

❌ B. Northern Blot

• Used for detecting RNA, not genomic DNA insertions.

❌ C. Microarray

• Used for gene expression analysis, not for detecting specific viral DNA integration.

Conclusion:

Southern blotting remains the gold standard for detecting viral DNA insertions into the host genome. It is widely used in virology, gene therapy, and molecular diagnostics to study retroviral integrations, transgene stability, and genetic diseases.