Section 4: Bioprocess Engineering and Process Biotechnology
Mass transfer in bioprocesses (kLa)
Subtopic: Fundamentals of Mass transfer in bioprocesses (kLa)
Question Statement:
DNA synthesized from an RNA template is called
Options:
(A) recombinant DNA.
(B) transcript.
(C) T-DNA.
(D) complementary DNA.
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2020 Q.17)**
**1. Governing Concept**:
- **Topic**: Molecular Biology & Recombinant DNA Tools
- DNA synthesized in vitro from a mature messenger RNA (mRNA) template via the catalytic action of the enzyme **reverse transcriptase** (RNA-dependent DNA polymerase) is called **complementary DNA (cDNA)**.
- Unlike genomic DNA, cDNA lacks non-coding introns and is used to construct cDNA libraries and express eukaryotic proteins in prokaryotic hosts.
**2. Option Analysis**:
- **Option (A) [recombinant DNA] is INCORRECT**: Chimeric DNA formed by joining fragments from different sources.
- **Option (B) [transcript] is INCORRECT**: An RNA molecule synthesized from a DNA template.
- **Option (C) [T-DNA] is INCORRECT**: Transferred DNA from the *Agrobacterium* Ti plasmid.
- **Option (D) [complementary DNA] is CORRECT**: The specific term for reverse-transcribed DNA.
**3. Final Answer**:
- **Correct Choice**: **D**
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