NCERT Solutions Class 12 Biology Chapter 9 Biotechnology: Principles and Processes

In Chapter 9, Biotechnology: Principles and Processes, of Class 12 Biology, students learn how biological systems and organisms are used to develop useful products through scientific techniques. The chapter also explains various concepts including the basic principles behind genetic engineering, the tools used in biotechnology, and the steps involved in creating recombinant DNA. 

To assist students in mastering these topics, ALLEN is providing quality NCERT Solutions that provides logical, step-by-step guides. Our expert faculty has designed these materials to focus on clarity, ensuring that complex concepts like gel electrophoresis and bioprocess engineering are easy to understand and memorize. By following the structured explanations provided by ALLEN, students can align their answers with the specific requirements of the CBSE marking scheme, building the confidence and accuracy needed to excel in both their school finals and competitive medical entrance tests.

1.0Download NCERT Solutions Class 12 Biology Chapter 9 Biotechnology: Principles and Processes : Free PDF

This chapter explains how modern biotechnology works, from gene isolation to product formation, in a simple and structured way. The NCERT Solutions for Class 12 Biology Chapter 9 Biotechnology: Principles and Processes help students revise key tools and steps and practise textbook questions easily. Download the free PDF now to study anytime and prepare confidently for exams.

2.0Key Concepts of Class 12 Biology Chapter 9 Biotechnology: Principles and Processes

The chapter focuses on understanding the methods and tools used in genetic engineering. Some of the key lessons covered in this chapter are given below:

• Principles of Biotechnology: Understanding genetic engineering and bioprocess engineering as the two main foundations.
• Tools of Recombinant DNA Technology: Studying restriction enzymes, ligases, vectors, and host organisms.
• Isolation of Genetic Material: Learning how DNA is extracted and purified from cells.
• Polymerase Chain Reaction (PCR): Understanding how specific DNA segments are amplified.
• Cloning Vectors: Learning about plasmids and bacteriophages used to carry foreign DNA.
• Introduction of Recombinant DNA into Host: Studying methods like transformation and transfection.
• Bioreactors: Understanding how large-scale production of biological products is carried out.
• Downstream Processing: Learning how products are separated and purified after production.

3.0NCERT Class 12 Biology Chapter 9 Biotechnology: Principles and Processes : Detailed Solutions

1. Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet). 

Ans: Some of the recombinant proteins used in medical practice for therapeutic uses are:

2. Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces. 

Ans:

3. From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know? 

Ans:  In molecular size, DNA is significantly bigger than the enzymes.

• While enzymes are proteins made up of hundreds to a few thousand amino acids, DNA molecules, especially chromosomal DNA, are extremely long polymers made up of millions to billions of nucleotides.
• In laboratory techniques like gel electrophoresis, DNA fragments move more slowly than enzymes, showing that DNA has a much larger molecular size.
• The human genome alone contains about 3 billion base pairs, which is far larger than the size of any enzyme molecule.
• While a typical enzyme might have a molecular weight in the range of 10⁴ to 10⁵ Daltons, a single human chromosome (one DNA molecule) has a molecular weight in the range of 10¹¹Daltons.

4. What would be the molar concentration of human DNA in a human cell? Consult your teacher. 

Ans: The amount of DNA present in a diploid human cell is approximately 6.6 picograms (6.6 × 10⁻¹² g). The human genome contains about 6.6 × 10⁹ base pairs, and the average molecular weight of one base pair is 660 g mol⁻¹.

So, the molecular weight of human DNA is:

6.6 × 10⁹ × 660 = 4.356 × 10¹² g mol⁻¹

The number of moles of DNA in one cell is:

$\frac{6.6\times 10^{-12}}{4.356\times 10^{12}}\approx 1.5\times 10^{-24}mol$

The average volume of a human cell is about 10⁻¹² litres.

Therefore, the molar concentration of DNA in a human cell is:

$\frac{1.5\times 10^{-24}}{10^{-12}}=1.5\times 10^{-12}M$

5. Do eukaryotic cells have restriction endonucleases? Justify your answer.

Ans: No,  eukaryotic cells do not have restriction endonucleases. Restriction endonucleases are enzymes that recognise and cut foreign DNA at specific nucleotide sequences. They are part of a defence mechanism in prokaryotes (bacteria), where they protect the cell from invading viral DNA (bacteriophages).

Eukaryotic cells, however, do not face such frequent DNA invasion by bacteriophages. Therefore, they do not require restriction enzymes for protection. They use other mechanisms like the immune system and RNA interference, to defend against foreign genetic material.

6. Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks? 

Ans: Besides better aeration and mixing, stirred tank bioreactors have several advantages over shake flasks:

• They allow better control of growth conditions such as temperature, pH, and dissolved oxygen.
• They are suitable for large-scale production, making them useful for industrial and commercial processes.
• The culture can be continuously monitored and sampled without having to disturb the system.
• They provide uniform distribution of nutrients and microorganisms, leading to higher product yield.

7. Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules. 

Ans: A palindromic DNA sequence is a sequence of base pairs that reads the same in the 5′ → 3′ direction on both strands, following base-pairing rules (A–T and G–C).

Examples:

(a) 5′ — GAATTC — 3′

3′ — CTTAAG — 5

(b) 5′ — GGATCC — 3′

3′ — CCTAGG — 5′

(c) 5′ — AAGCTT — 3′

3′ — TTCGAA — 5′

(d) 5′ — CCCGGG — 3′

3′ — GGGCCC — 5′

(e) 5′ — ATGCAT — 3′

3′ — TACGTA — 5′

8. Can you recall meiosis and indicate at what stage a recombinant DNA is made? 

Ans: Yes, recombinant DNA is formed during meiosis in the Prophase I stage, specifically in the pachytene sub-stage.

During the pachytene stage, homologous chromosomes pair and undergo crossing over. Here, the segments of DNA are exchanged between non-sister chromatids. This exchange results in the formation of new combinations of genes. These newly formed genes are known as recombinant DNA.

9. Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker? 

Ans: A reporter enzyme helps in the visual identification of transformed host cells that have taken up foreign DNA.

In this method, a reporter gene (such as lacZ) is linked with the foreign DNA and inserted into the host cell. If transformation occurs, the reporter gene is also expressed and produces an enzyme that causes a visible change, like a colour reaction when a specific substrate is added.

Example: Cells expressing the lacZ gene produce β-galactosidase, which turns the substrate X-gal blue. Thus, blue colonies indicate transformed cells, while non-transformed cells remain colourless.

10. Describe briefly the following: 

(a) Origin of replication 

(b) Bioreactors 

(c) Downstream processing 

Ans: (a) Origin of replication:  The origin of replication (ori) is a specific sequence in the DNA from where DNA replication begins. It is the site at which the DNA strand opens up and replication machinery attaches to start copying the DNA. In cloning vectors, the ori also controls the number of copies of the inserted foreign DNA in the host cell.

(b) Bioreactors : Bioreactors are large vessels in which microorganisms, plant cells, or animal cells are grown under controlled conditions to produce useful biological products like enzymes, vaccines, antibiotics, or hormones. They provide optimum temperature, pH, nutrients, oxygen, and mixing to ensure maximum growth and product formation.

(c) Downstream processing : Downstream processing refers to the series of steps used to separate, purify, and formulate the final product after the biological reaction is complete. It includes processes like filtration, centrifugation, purification, and packaging to make the product safe and suitable for commercial or medical use.

11. Explain briefly 

(a) PCR 

(b) Restriction enzymes and DNA 

(c) Chitinase 

Ans:

(a) PCR : PCR(Polymerase Chain Reaction) is a technique used to make multiple copies of a specific segment of DNA in a short time. It involves three main steps: denaturation (separation of DNA strands), annealing (binding of primers), and extension (synthesis of new DNA strands by DNA polymerase). This process is repeated in cycles to amplify the DNA exponentially.

(b) Restriction enzymes and DNA : Restriction enzymes are the molecular scissors that cut DNA at specific nucleotide sequences called recognition sites. They are mainly found in bacteria and are used to cut both the foreign DNA and vector DNA at the same sites, producing compatible ends. This helps in joining the desired DNA fragment into a cloning vector.

(c) Chitinase : Chitinase is an enzyme that breaks down chitin, which is a major component in the cell wall of fungus. In biotechnology, it is used to digest the cell wall of fungi, which allows the release of cellular contents such as DNA or proteins for further study or genetic manipulation.

12. Discuss with your teacher and find out how to distinguish between 

(a) Plasmid DNA and Chromosomal DNA 

(b) RNA and DNA 

(c) Exonuclease and Endonuclease

Ans: (a) Plasmid DNA and Chromosomal DNA 

(b) RNA and DNA 

(c) Exonuclease and Endonuclease

4.0Key Features and Benefits of Class 12 Biology Chapter 9 Biotechnology: Principles and Processes

• Clear explanations help students understand how genes can move from a lab setup into a living host organism.
• Real-life examples connect textbook biotechnology concepts with medicines, vaccines, and industrial products.
• Diagrams and flow-based answers improve clarity while revising complex laboratory procedures.
• Structured practice builds confidence in handling process-driven and application-based board exam questions.
• Concept clarity supports early preparation for NEET and future studies in genetic engineering fields.
• Simple language helps students remember technical terms without feeling overwhelmed by scientific jargon.