NCERT Class 12 Biotechnology Biotechnology: Chapter 3 — Gene Cloning
This chapter introduces Gene Cloning, a fundamental procedure in biotechnology for producing desired products. It explains the traditional method of transferring a gene of interest into a host cell via a vector to create multiple copies. The chapter details the technological advancements in genetic engineering that enable DNA analysis, gene isolation, the creation of recombinant DNA molecules using enzymes and vectors like plasmids, and the introduction of these into hosts like bacteria for cloning. It covers the identification of candidate genes, the challenges in isolating them from large genomes, and methods like deducing DNA sequences from amino acid sequences or synthesizing cDNA from mRNA. The initial steps of isolating nucleic acids from organisms are also discussed, highlighting the challenges involved.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Biotechnology |
| Book | Biotechnology |
| Chapter | Chapter 3 — Gene Cloning |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 3 minutes |
| Word count | 573 |
Learning outcomes
- Understand the concept and importance of gene cloning in biotechnology.
- Identify the steps involved in traditional gene cloning.
- Recognize the role of genetic engineering in gene cloning.
- Learn about the challenges and methods for identifying and isolating candidate genes.
- Understand the initial requirement of nucleic acid isolation for molecular biology experiments.
Vocabulary
| Word | Meaning |
|---|---|
| Gene cloning | A procedure to use a gene for its product, involving transfer to a host cell via a vector to create many copies. |
| Vector | A DNA molecule used to carry a foreign gene into a host cell. |
| Host cell | A cell that receives and replicates a foreign DNA molecule. |
| Recombinant DNA (rDNA) | DNA formed by combining genetic material from different sources. |
| Plasmid | An autonomously replicating, circular DNA molecule found in bacteria, often used as a vector. |
| Nucleic acids | Biological macromolecules, DNA and RNA, essential for storing and transmitting genetic information. |
| cDNA | Complementary DNA, synthesized from an mRNA template. |
| Reverse transcriptase | An enzyme that synthesizes DNA from an RNA template. |
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Practice questions
- What is the primary purpose of gene cloning in biotechnology? Answer: To produce many copies of a specific gene for its characterization and future application, often to obtain its product.
- What are the two main components involved in the traditional gene cloning process? Answer: A gene of interest (DNA fragment) and a vector.
- Why is identifying a candidate gene considered a formidable problem? Answer: Because genomes are very large (billions of base pairs), making it difficult to locate a specific gene of interest (which is much smaller).
- Name one method used to synthesize a candidate gene. Answer: Synthesizing cDNA from mRNA using reverse transcriptase.
- What is the first requirement for any molecular biology experiment mentioned in the text? Answer: Isolation of nucleic acids (DNA and RNA) from organisms.
Practice MCQs
Q1. Which of the following is a key step in traditional gene cloning?
Explanation: Traditional gene cloning involves using a vector to transfer the gene of interest into a host cell, enabling its replication.
Q2. What is an example of an autonomously replicating vector used in rDNA technology?
Explanation: Plasmids are commonly used as vectors in recombinant DNA technology because they can replicate independently within a host cell.
Q3. The difficulty in searching for a gene of interest in a human genome is compared to:
Explanation: The text explicitly compares the difficulty of finding a small gene within a vast genome to searching for a needle in a haystack.
Q4. Which enzyme is used to synthesize cDNA from mRNA?
Explanation: Reverse transcriptase is the enzyme responsible for synthesizing DNA from an RNA template, a crucial step in creating cDNA.
Q5. What is a major challenge encountered during the isolation of nucleic acids?
Explanation: The text mentions that both DNA and RNA are present in cells, and their isolation can be challenging due to cellular enzymes that might degrade them.
Frequently asked questions
What is gene cloning and why is it important in biotechnology?
Gene cloning is a process to create multiple copies of a specific gene, often to produce its desired product. It's crucial for various applications in the biotechnology industry and for genetic engineering.
What is the traditional method of gene cloning?
It involves transferring a DNA fragment containing the gene of interest into a host cell using a vector, allowing the host to replicate many copies of the gene.
What are the main challenges in identifying a candidate gene?
The primary challenge is the sheer size of genomes; finding a specific gene, which is much smaller than the entire genome, is extremely difficult.
How can a candidate gene be synthesized if direct isolation is difficult?
One method is to isolate mRNA for the desired gene, then use reverse transcriptase to synthesize complementary DNA (cDNA), which can then be cloned.
What is a plasmid and its role in gene cloning?
A plasmid is a small, circular DNA molecule found in bacteria. It is often used as a vector to carry the gene of interest into a host cell for replication.
What is the first step required for any molecular biology experiment involving genes?
The first requirement is the isolation of nucleic acids, specifically DNA and RNA, from the organism.
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NCERT Class 12 Biotechnology — Biotechnology — Chapter 3 — Gene Cloning. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.