In which of the process is both the DNA strand transcribed ?

Options

A. PCR
B. DNA replication
C. RNAi
D. Southern blotting

Answer

To determine in which process both DNA strands are transcribed, we need to analyze the options provided:

1. **PCR Technique**: The Polymerase Chain Reaction (PCR) is a method used to amplify DNA. It does not involve transcription, as it simply replicates DNA using primers and DNA polymerase. Therefore, this option is incorrect.

2. **DNA Replication**: This is the process by which DNA makes a copy of itself during cell division. While both strands of DNA are involved in the replication process, transcription specifically refers to the synthesis of RNA from a DNA template. In DNA replication, both strands serve as templates for new DNA synthesis, but only one strand is transcribed into RNA at a time. Thus, this option is also incorrect.

3. **RNA Interference (RNAi)**: RNA interference is a biological process where RNA molecules inhibit gene expression or translation by neutralizing targeted mRNA molecules. In this case, both strands of DNA can be transcribed into RNA, making this option a candidate for our answer.

4. **Southern Blotting**: This is a laboratory technique used to detect specific DNA sequences in a sample. It involves the transfer of DNA fragments from a gel to a membrane and does not involve transcription. Hence, this option is incorrect.

After analyzing all the options, the only process in which both DNA strands are transcribed is **RNA Interference (RNAi)**.

### Final Answer:
**RNA Interference (RNAi)**