38. Which one of the recombinant DNA technique is almost obsolete?
- Long DNA synthesis
- DNA sequencing
- Polymerase Chain Reaction
- cDNA cloning
Title: Obsolete Recombinant DNA Technique: Long DNA Synthesis Explained (MCQ Solved)
Long DNA synthesis is the recombinant DNA technique that is almost obsolete due to its labor-intensive nature and replacement by modern methods like PCR and gene synthesis.
Correct Answer: Long DNA Synthesis
Early long DNA synthesis involved chemical oligonucleotide assembly (e.g., phosphodiester or phosphoramidite methods) to build DNA strands over 1000 bp, but it was error-prone, low-yield, and time-consuming. Advances in PCR amplification, next-generation sequencing, and automated gene synthesis (e.g., Gibson assembly) have rendered it largely obsolete for routine recombinant DNA work.
Why It’s Obsolete
Traditional long DNA synthesis required manual coupling of nucleotides with high error rates (~1-2% per base), necessitating purification and error correction steps. Modern alternatives like high-fidelity PCR or commercial gene synthesis services produce accurate long DNA (up to 10 kb+) quickly and affordably, making the old method unnecessary in most labs.
Explanation of All Options
Technique Status Explanation Long DNA Synthesis Almost Obsolete Labor-intensive chemical synthesis of long DNA sequences (>1000 bp); replaced by PCR and automated synthesis due to inefficiency and errors. DNA Sequencing Essential & Evolving Sanger sequencing evolved into NGS; remains core to genomics, cloning verification, and rDNA workflows. Polymerase Chain Reaction (PCR) Fundamental Amplifies DNA exponentially; advanced variants (qPCR, digital PCR) keep it indispensable for cloning, diagnostics. cDNA Cloning Still Used Converts mRNA to cDNA for expression libraries; partially supplemented by RNA-seq but vital for protein studies.
