CBSE Class 12 Biology Exemplar Chapter 11: Biotechnology Principles and Processes NCERT Solutions

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NCERT Solutions PDF Class 12 PDF

This chapter, Biotechnology Principles and Processes, delves into the fundamental concepts and techniques of biotechnology. Students will explore the mechanisms behind processes like the rising of dough, the roles of enzymes such as restriction enzymes and DNA ligase in genetic engineering, and methods for transferring genetic material between organisms. The solutions cover the visualization of DNA after gel electrophoresis and the construction of recombinant DNA molecules. These NCERT Solutions are designed to provide clear, step-by-step explanations, helping students grasp complex biotechnological principles and prepare effectively for their examinations.

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BoardCBSE
ClassClass 12
SubjectBiology Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 11

Chapter summary

Chapter 11, Biotechnology Principles and Processes, focuses on core biotechnological applications and tools. It explains the role of microorganisms in fermentation (like yeast in dough rising), the function of enzymes in DNA manipulation (endonucleases, exonucleases, ligases), and methods of gene transfer (transduction). The solutions also touch upon visualizing DNA using gel electrophoresis and ethidium bromide, and the essential components for creating recombinant DNA. This chapter is crucial for understanding modern genetic engineering techniques.

Learning outcomes

  • Understand the role of yeast in fermentation and dough rising.
  • Differentiate between exonucleases and endonucleases in DNA processing.
  • Explain the process of transduction for genetic material transfer.
  • Describe the visualization of DNA fragments after gel electrophoresis.
  • Identify the key enzymes and steps involved in creating recombinant DNA.

Topics covered

Paper topics

  • Fermentation
  • Yeast in Dough Rising
  • Enzymes in Biotechnology
  • Exonucleases
  • Endonucleases
  • DNA Ligase
  • Gene Transfer
  • Transduction
  • Bacterial Conjugation
  • Transformation
  • Agarose Gel Electrophoresis
  • Recombinant DNA Technology

Important topics

  • Role of Enzymes in DNA Manipulation (Restriction Enzymes, Ligase)
  • Mechanisms of Gene Transfer (Transduction)
  • Visualization of DNA (Gel Electrophoresis)
  • Recombinant DNA Molecule Preparation

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Questions and Solutions

Q. 1

Rising of dough is due to
  1. multiplication of yeast
  2. production of CO2
  3. emulsification
  4. hydrolysis of wheat flour starch into sugars
Solution: The rising of dough is primarily caused by the metabolic activity of yeast, specifically Saccharomyces cerevisiae. When yeast is added to flour and water, it undergoes fermentation. During this process, yeast consumes sugars present in the flour and produces carbon dioxide (CO2) gas and ethanol. The CO2 gas gets trapped within the gluten network of the dough, causing it to expand and become light, soft, and spongy. This process is essential for making bread and other baked goods.

Q. 2

An enzyme catalysing the removal of nucleotides from the ends of DNA is
  1. endonuclease
  2. exonuclease
  3. DNA ligase
  4. Hind II
Solution: Enzymes that remove nucleotides from the ends of DNA are called exonucleases. Restriction enzymes, which are crucial in genetic engineering, are a type of nuclease. They are broadly classified into two types: exonucleases, which degrade DNA from the ends, and endonucleases, which cut DNA at specific internal sites. DNA ligase, on the other hand, is an enzyme that joins DNA fragments together. Hind II is a specific type of restriction endonuclease.

Q. 3

The transfer of genetic material from one bacterium to another through the mediation of a vector like virus is termed as
  1. transduction
  2. conjugation
  3. transformation
  4. translation
Solution: The process described is transduction. Transduction is a mechanism of horizontal gene transfer in bacteria where genetic material is transferred from one bacterium to another by a virus, specifically a bacteriophage. The virus mistakenly packages bacterial DNA into its capsid and injects it into a new host bacterium. Conjugation involves direct cell-to-cell contact for DNA transfer, typically plasmids. Transformation is the uptake of foreign DNA from the environment by a bacterial cell. Translation is the process of protein synthesis from mRNA.

Q. 4

Which of the given statement is correct in the context of observing DNA separated by agarose gel electrophoresis?
  1. DNA can be seen in visible light.
  2. DNA can be seen without staining in visible light.
  3. Ethidium bromide stained DNA can be seen in visible light.
  4. Ethidium bromide stained DNA can be seen under exposure to UV light.
Solution: DNA fragments separated by agarose gel electrophoresis are not visible under normal visible light because DNA does not absorb visible light. To visualize the DNA bands, the gel is typically stained with a fluorescent dye called ethidium bromide. When this stained gel is exposed to ultraviolet (UV) light, the ethidium bromide intercalated within the DNA fragments fluoresces, making the DNA bands visible as bright orange bands against a darker background.

Q. 5

'Restriction' in restriction enzyme refers to
  1. cleaving of phosphodiester bond in DNA by the enzyme
  2. cutting of DNA at specific position only
  3. prevention of the multiplication of bacteriophage in bacteria
  4. All of the above
Solution: The term 'restriction' in restriction enzyme originates from their role in the 'restriction-modification system' found in bacteria. This system acts as a defense mechanism against foreign DNA, such as that from invading bacteriophages. The restriction enzyme specifically cuts (restricts) the foreign DNA at particular recognition sites, thereby preventing its replication and propagation within the bacterial cell. While they do cleave phosphodiester bonds and cut at specific positions, the primary meaning of 'restriction' relates to this protective function against foreign DNA.

Q. 6

Which of the following is not required in the preparation of a recombinant DNA molecule?
  1. Restriction endonucleases
  2. DNA ligase
  3. DNA fragments
  4. E. coli
Solution: The preparation of a recombinant DNA molecule involves several key components and enzymes. Restriction endonucleases are required to cut both the vector DNA and the DNA containing the gene of interest, creating compatible ends. DNA ligase is essential for joining the gene of interest into the vector DNA, forming a stable recombinant molecule. DNA fragments, including the vector and the insert DNA, are the fundamental building blocks. While E. coli (or another suitable host organism) is necessary for cloning and amplifying the recombinant DNA, it is not directly required in the test tube preparation of the recombinant DNA molecule itself. Therefore, E. coli is the component not directly involved in the molecular construction phase.

Common mistakes

  • Confusing the functions of exonucleases and endonucleases.
  • Misunderstanding the mechanism of transduction compared to other gene transfer methods.
  • Incorrectly identifying the conditions or stains needed for DNA visualization.
  • Overlooking the necessity of DNA ligase in recombinant DNA technology.

Revision tips

  • Focus on the specific roles of enzymes like restriction enzymes and DNA ligase.
  • Review the different methods of gene transfer and their mediators.
  • Understand the steps involved in visualizing DNA after gel electrophoresis.
  • Practice identifying the correct components needed for recombinant DNA preparation.

Practice MCQs

Q1. What is the primary reason for dough rising when yeast is added?

Q2. Which enzyme is responsible for removing nucleotides from the ends of a DNA molecule?

Q3. The process of transferring genetic material from one bacterium to another using a virus as a vector is known as:

Q4. How are DNA fragments separated by agarose gel electrophoresis typically visualized?

Q5. The term 'restriction' in restriction enzyme primarily refers to:

Q6. Which of the following is NOT essential for the preparation of a recombinant DNA molecule?

Frequently asked questions

What is the main principle behind dough rising?

Dough rises due to the production of carbon dioxide (CO2) gas by yeast during fermentation. This gas gets trapped in the dough, causing it to expand and become spongy.

What is the difference between exonucleases and endonucleases?

Exonucleases remove nucleotides from the ends of a DNA molecule, while endonucleases cut DNA at specific internal positions.

How is genetic material transferred between bacteria using viruses?

This process is called transduction, where a virus (bacteriophage) acts as a vector to carry genetic material from one bacterium to another.

How can we see DNA after it has been separated by gel electrophoresis?

DNA is first stained with a fluorescent dye like ethidium bromide and then visualized as glowing bands under UV light.

What are the essential components for creating recombinant DNA?

The essential components are restriction endonucleases to cut DNA, DNA fragments (gene of interest and vector), and DNA ligase to join these fragments together.

Why are restriction enzymes called 'restriction' enzymes?

The term 'restriction' refers to their original discovered function in bacteria: to restrict the multiplication of foreign DNA, such as that from bacteriophages, by cutting it.

Important links

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