NCERT Solutions Class 12 Biology Chapter 11

NCERT Solutions Class 12 Biology Chapter

Biology is the branch of science concerned with studying living organisms and their functioning. Biologists generally study the structure, function, growth, origin, evolution, and distribution of living species. It is a vast natural science with some unifying components that bring it together as a single, coherent topic. Medicine, nursing and allied health, pharmacy and pharmacology, dentistry, and veterinary medicine are among the occupations that require biology as a foundation.

Class 12th Biology Chapter 11 is Biotechnology: Principles and Processes. This chapter dives into the ideas and concepts that underpin Biotechnology’s foundation and best practices. These are essential skills that a student must acquire if they wish to continue their studies in Biology. The numerous rules and practices utilised in Biotechnology are the focus of this chapter.

Biology may be both enjoyable and stressful. The way a student decides to go about it determines the course of this subject. Therefore, choosing the right platform to learn a subject like Biology is very important. Extramarks have provided NCERT Solutions for Chapter 11 biology Class 12. These answers help students understand the main idea, course material, and chapter questions.

Not just NCERT Solutions Class 12 Biology Chapter 11, Extramarks is a powerhouse of quality study material. Extramarks website houses material such as NCERT books, CBSE revision notes, CBSE sample papers, and CBSE previous year question papers for all classes for the student’s usage.

Key Topics Covered in NCERT Solutions Class 12 Biology Chapter 11

Mentioning below all the key topics that are covered in NCERT Solutions Class 12 Biology Chapter 11- Biotechnology- Principles and Processes:

Introduction to Biotechnology
Principles of Biotechnology
Recombinant DNA Technology-Tools for genetic engineering
Cloning Vectors
Process and Recombination of DNA Technologies

Let us look at Extramarks in-depth information on each subtopic in NCERT Solutions Class 12 Biology Chapter 11- Biotechnology- Principles and Processes.

Introduction to Biotechnology

NCERT Solutions Class 12 Biology Chapter 11 describes Biotechnology as a vast branch of biology that involves developing, modifying, and producing valuable goods for human welfare using both the technology and the application of live organisms and their components. Karoly Ereky, an agricultural engineer, created the phrase “biotechnology” in 1919, earning him the title of “Father of Biotechnology.”

Principles of Biotechnology

NCERT Solutions Class 12 Biology Chapter 11 states that Biotechnology’s main principles, according to current biotechnology, are:

  • Genetic engineering: Genetic engineering is a technique for altering the DNA of a target organism to change its phenotypic.
  • Bioprocess engineering: Bioprocess engineering is the process of maintaining sterile conditions to support the growth of large quantities of desired microbes and other eukaryotic cells to produce new or modified biotechnological products such as antibiotics, and enzymes, vaccines, and other biotechnological products.

Recombinant DNA Technology-Tools for genetic engineering

NCERT Solutions Class 12 Biology Chapter 11 states that the following are some of the most common genetic engineering techniques:

  • First, the donor organism’s DNA is extracted as a fragment.
  • Next, the vector DNA is introduced into it.
  • It is then transferred to a suitable host.
  • Finally, in the host organism, the recombinant DNA is cloned.

Restriction enzymes, often known as molecular scissors, cut the DNA before inserting it into the vector. These restriction enzymes aid in the insertion of methyl groups into DNA, resulting in restricted digestion of their DNA. In addition, these enzymes can cleave DNA fragments at specific recognition sequences.


Ligases are the enzymes in charge of connecting the two DNA segments. In the presence of sticky ends, the ligation process takes place.

Separation and Isolation of DNA fragments

The separation of DNA fragments acquired during restriction is accomplished using the process known as gel electrophoresis.

Gel electrophoresis

When an electric current is conducted in an electric field, negatively charged DNA relocates through a porous polymer gel matrix to a positively charged electrode.


Because DNA fragments cannot be seen directly, they must first be stained with ethidium bromide (EtBr) and then subjected to UV light, producing DNA fluoresces.


The elution procedure entails removing the desired DNA fragments from the gel.

The above section of NCERT Solutions Class 12 Biology Chapter 11 describes various tools for genetic engineering. To get detailed notes on the same, refer to the Extramarks website today. 

Cloning Vectors

In the following section, NCERT Solutions Class 12 Biology Chapter 11 explains another vital topic, the process of Cloning.

Any DNA molecule responsible for conveying the intended gene into the host organism is referred to as a vector. Consider the plasmid. The plasmid is an extrachromosomal, self-replicating genetic substance in bacteria distinct from the rest of the chromosomal DNA. It facilitates the introduction of desired genes into the host cell. Plasmids have a replication origin, which is the location where the gene of interest is replicated as soon as it reaches the host cell. It also has the gene for antibiotic resistance.

A cloning vector must have some specific characteristics. These have been described below by NCERT Solutions Class 12 Biology Chapter 11:

  • Origin of Replication: The origin of replication is referred to as ORI. This aids in the replication of DNA fragments in the host cell, allowing the number of copies of DNA to be maintained.
  • Selectable marks to identify the transformed cells: The transformation is the process of introducing a fragment of DNA into the host cells.
  • Cloning site in the Cloning vector: Just one cloning site must be present to avoid complicating the cloning process. The ligation of foreign DNA is caused by the antibiotic resistance gene present as restriction sites. When the desired gene is inserted at the location of an antibiotic resistance gene, antibiotic resistance is lost. As a result, the recombinant plasmid loses its antibiotic resistance. As a result, recombinants can be chosen from non-recombinants.
  • The technique of inserting the desired gene into the coding section of DNA causes an enzyme to become inactive.

Process and Recombination of DNA Technologies

The recombinant DNA technology method is divided into various parts. These parts have been discussed below by NCERT Solutions Class 12 Biology Chapter 11:

  • Isolation of the genetic material: To isolate the DNA, the membrane around it must be removed. This may be accomplished with lysozyme enzymes, which break down the cell walls of bacteria and cellulase and chitinase. Ribonucleases may be used to isolate RNA, whereas proteases can be used to remove proteins. Finally, the acquired DNA is processed with ethanol to eliminate leftover contaminants. The DNA is then extracted as thin threads suspended in water.
  • Restriction digestion of the Isolated DNA: By using agarose gel electrophoresis, the restriction digestion of the DNA is accomplished. The desired gene is then inserted into the vector and bonded together with the aid of a ligase enzyme, resulting in the production of a recombinant DNA molecule.
  • Amplification of Interest gene using PCR: The Polymerase chain reaction can be used to amplify the target gene in DNA (PCR). The forward primer and the reverse primer are the two sets of primers required. The DNA polymerase enzyme is used to do DNA amplification.
  • Inserting Recombinant DNA into Host organism: The host cells must be more competitive to accept the recombinant DNA.
  • Expression of desired protein: The primary goal of recombinant DNA technology is to produce the desired protein. As a result, the protein produced is a recombinant protein.


Massive containers used to manufacture large amounts of recombinant protein are known as bioreactors. The bioreactors give the optimum development conditions (temperature, pH, substrate, salts, vitamins, oxygen) to generate the desired result.

Some parts of a Bioreactor

NCERT Solutions Class 12 Biology Chapter 11 provides below some essential parts of a Bioreactor:

  • Temperature control
  • Agitator
  • Oxygen control system
  • pH control
  • Foam control system
  • Inlet
  • Outlet
  • Sampling port

Bioreactors can be of two forms- Stirred bioreactors and Sparger.

Stirred type Bioreactor

The stirrer kind of bioreactor is made up of a stirrer with a curved base that helps mix the contents. It also helps the medium’s aeration.

Sparger type Bioreactor

The air is bubbled from the bioreactor’s base, resulting in the mixing and aeration of the contents in the sparger type of bioreactor.

NCERT Solutions Class 12 Biology Chapter 11 Exercise and Solutions

Students can register with Extramarks and get NCERT Solutions for all chapters and other study tools, including previous year’s question papers, revision notes, extra problems, and more, on the Extramarks website. Click on the below links to view NCERT Solutions Class 12 Biology Chapter 11:

By getting access to NCERT Solutions Class 12 Biology Chapter 11, students can easily understand all the concepts of Biotechnology- Principles and Processes.

Key Features of NCERT Solutions Class 12 Biology Chapter 11

Extramarks’ NCERT Solutions include all the major concepts and subjects required for the CBSE board examinations. Therefore, to perform well in the forthcoming board examinations, students are advised to go over NCERT Solutions available on the Extramarks website. But why Extramarks, you ask? Here’s why:

  • Experts at Extramarks have years of experience and  they know what a student requires to comprehend a chapter. Therefore, it is what they present in the notes and solutions on the Extramarks website.
  • These solutions help students in revising their concepts and in managing time effectively 
  • These solutions have been made, keeping in mind all the guidelines of CBSE.

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


10 recombinant proteins used in medical practice along with their therapeutic value are as follows:

Protein Therapeutic Value
1. Growth Hormone Promoting growth in an individual
2 Human Insulin Treatment for type I diabetes mellitus
3 Erythropoietin Treatment of anaemia during renal failure
4 Follicle-stimulating hormone Stimulation of ovarian follicle growth
5 Interferon α Treatment of chronic Hepatitis C
6 Insulin-like growth factor Dwarfism
7 Tissue Plasminogen Activator Thrombosis
8 Blood clotting Factor VIII, Haemophilia
9 DNase I Treatment of cystic fibrosis
10 Interferon β Treatment of multiple sclerosis

Q.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.


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


DNA is bigger in the molecular size as compared to enzymes. Because, DNA contains the entire genetic information which is first transcribed into RNA by transcription and then translated into proteins by the process of translation with the help of mRNA, tRNA and ribosomes. A macromolecule DNA has many genes which code for numerous proteins while on the other hand, enzymes are protein molecules which are coded by genes – a small stretch of genomic DNA molecule that can be transcribed into RNA.

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


Molar concentration is the concentration measured by the number of moles of solute per litre of solution. The number of moles of human DNA in a human diploid cell will be calculated as follows:

*Total number of chromosomes × 6.023 × 1023

= 46 × 6.023 × 10­­­23

=2.77 ×1025 Moles

However, since the volume of solute in each cell varies depending upon the shape, size and type, one cannot calculate the molar concentration of DNA in each human cell.

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


No, eukaryotic cells do not have restriction endonucleases.

Justification: Restriction endonucleases are enzymes present in bacteria that restrict the growth of bacteriophages (viruses that infect the bacteria) by cutting DNA at or near a specific recognition nucleotide sequence called restriction site. They are the self-defence mechanisms of the bacteria against the invading virus. The bacterial host DNA is protected from the action of these restriction endonucleases because of certain modifications like methylations present on its host DNA.

The eukaryotic cells have another class of endonucleases that are involved in the cutting of the DNA backbone. They are not called restriction endonucleases. One example is topoisomerase that helps in releasing the tension of supercoiled DNA structure at the time of replication.

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


To produce recombinant proteins, bacterial cultures carrying the recombinant gene expressing the desired protein are grown in lab or at industrial scale. Small volumes of culture can be grown in shake flask. However, to produce large quantities, stirred flask bioreactors are used. Besides having better aeration and mixing properties, the other advantages of stirred tank bioreactors over shake flasks are:

  1. Air or oxygen can be bubbled in a controlled manner through the reactor.
  2. Foam control system can break excess foam produced during stirring.
  3. Temperature control system can help control the temperature to the desired levels.
  4. pH control system helps control the pH to the desired levels.
  5. Sampling ports of the bioreactor help take small volumes of the sample to test at periodic intervals.

Q.7 Write 5 examples of palindromic DNA sequence by following base pair rules. Better try to create a palindromic sequence by following base-pair rules.


A palindromic sequence is a sequence of DNA that is same when read from 5′ to 3′ end on one strand 3′ or to 5′ on the complementary strand. These are recognised by restriction endonucleases and are sites for their enzymatic activity, thus breaking the DNA right at that site. Some examples of palindromic DNA sequences are as follows:

  • EcoRI : 5’ – G A A T T C – 3’

          3’ – C T T A A G – 5’

  • BamHI: 5’ – G G A T C C – 3’

           3’ – C C T A G G– 5’

  • HindIII: 5’ – A A G C T T – 3’

           3’ – T T C G A A– 5’

  • PstI: 5’ – C T G C A G – 3’

           3’ – G A C G T C – 5’

  • EcoRV: 5’ – G A T A T C – 3’

           3’ – C T A T A G – 5’

  • Self-designed palindromic sequence: 5’ – C C A T G G– 3’

           3’ – G G T A C C– 5’

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


Meiosis is a type of cell division necessary for sexual reproduction in eukaryotes. The number of sets of chromosomes is reduced to half of the original number at the end of meiosis. Meiotic division occurs in two stages, meiosis I and meiosis II. During the first stage, in a diploid cell, homologous chromosomes pair up and exchange genetic material with each other in a process called crossing over. The crossing over happens during the pachytene stage of Prophase I of Meiosis I. Thus, it is at the pachytene stage when the recombination occurs.

Q.9 Can you think about how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to their role as a selectable marker?


A reporter gene is a gene that can be attached to a regulatory sequence of another gene of interest. Genes were chosen as reporter genes confer certain easily identifiable or measurable properties in organisms expressing them. They give an indication of whether a certain gene has been taken up by or expressed in the cell or not and therefore they act as a selectable marker.

β-galactosidase gene is one such reporter gene used widely as a selectable marker. The recombinant DNA carrying the gene of interest is inserted within the coding sequence of the β-galactosidase gene present in the host cell, resulting in the inactivation of the enzyme (insertional inactivation). Thus, in the presence of chromogenic substrate, the transformed cells, which have received the gene of interest, do not produce any colour and give white colonies since the β-galactosidase gene has been inactivated. However, the cells, that did not receive the gene of interest, still carry a functional copy of the β-galactosidase gene, thus producing functional enzyme and give blue colour in the presence of chromogenic substrate. This way, recombinants can be distinguished from non-recombinants on the basis of their ability to produce colour in the presence of chromogenic substrate.

Q.10 Describe briefly the following:

  1. Origin of replication
  2. Bioreactors
  3. Downstream processing


  1. Origin of replication: The origin of replication is a specific sequence in a genome at which replication or duplication of DNA is initiated. DNA replication may proceed from this point bidirectionally or unidirectionally. The specific structure of the origin of replication varies from species to species, but all share some common characteristics. The pre-replication complex binds at the replication origin and initiates the process of replication by unwinding the DNA. The origin of replication sequences have been exploited by scientists in the process of cloning by linking any foreign DNA with the origin of replication, thus this foreign DNA can replicate and multiply itself in the host organism.
  2. Bioreactors: One of the major applications of genetic engineering is the production of recombinant proteins. These are proteins that are produced in the heterologous host after cloning the gene of interest in a suitable vector and expressing the protein under the right conditions in a new host. These host cells can be grown at a small scale in the laboratory in shake flasks but such small volumes cannot yield a good amount of protein product. To produce such proteins in large amounts, bioreactors have been developed where large volumes (100-1000 litres) of culture can be processed under desired and controlled conditions. These are the vessels where the added raw material is converted into specific products using microbial, plant, animal or human cells. It provides the optimal conditions for achieving the desired product by providing optimal growth conditions (temperature, pH, substrate, salts, vitamins, oxygen). A stirred tank bioreactor is the most common kind of bioreactor which provides very good aeration and mixing of all the constituents.
  3. Downstream processing: Downstream processing is the recovery and purification of biosynthetic products from natural sources such as animal or plant tissue or fermentation broth. It also includes the recycling of components that can be used again and, the proper treatment and disposal of waste. After completion of a biosynthetic stage, the recombinant product needs to be subjected to a series of processes before it can be marketed as a finished product. These include separation and purification of the product from the bioreactor. The product is mixed with various other things depending upon the nature of the product e.g. preservatives. Such mixed formulations are subjected to clinical trials in case of drugs. Strict quality control testing is required for each product. This downstream processing and quality control testing vary from product to product.

Q.11 Explain briefly:

  1. PCR
  2. Restriction enzymes and DNA
  3. Chitinase


  1. PCR: PCR (Polymerase Chain Reaction) is a revolutionary method developed by Kary Mullis in the 1980s. It is based on the ability of enzyme DNA polymerase to synthesise new strand of DNA complementary to the template strand. Since DNA polymerase can add a nucleotide only onto a preexisting 3′-OH group, it needs a primer (a small stretch of DNA) to which it can add the first nucleotide. This requirement makes it possible to designate a specific region of template sequence that the scientist wants to amplify. At the end of the PCR reaction, billions of copies of the specific sequence are obtained. PCR reaction requires a DNA template, DNA polymerase, primers and dNTPs (deoxynucleotide triphosphate). It consists of the following steps which are repeated for about 30-40 cycles:
  • Denaturation: Carried out at 94°C to denature the DNA.
  • Annealing: To allow the primer DNA to bind to the denatured DNA as per the base-pairing rule.
  • Extension: Carried out at 72°C where free dNTPs are sequentially added to the growing chain using the template DNA sequence.

Taq polymerase derived from Thermas aquaticus is a commonly used DNA polymerase, in PCR reactions because it is highly thermostable. It can tolerate high temperatures like 94°C during the denaturation step.

  1. Restriction enzymes and DNA: Restriction enzymes are enzymes present in bacteria that inhibit the growth of bacteriophages inside the host bacteria and thus, act as a self-defence machinery of the bacteria. They recognise specific sequences in the DNA, called restriction sequence and cut the DNA within or around it depending upon the nature of the restriction enzyme. They inspect the length of the DNA sequence and once the restriction sequence is found, they bind to the DNA and cut each of the two strands of the double helix at a specific point in the sugar phosphate backbone.

The convention for naming these enzymes is as follows: the first letter of the name comes from the genus and the second two letters from the species of the prokaryotic cell from which they were isolated, e.g. EcoRI comes from Escherichia coli RY 13. In EcoRI, R is derived from the name of the strain. Roman numbers following the name indicate the order in which the enzymes were isolated from that strain of bacteria.

Restriction enzymes are extensively used in genetic engineering to form recombinant molecules of DNA, which are composed of DNA from different sources/genomes.

  1. Chitinase: Chitinases are digestive enzymes that break down glycosidic bonds in chitin. Chitin composes the cell walls of fungi and exoskeletal elements of some animals (including worms and arthropods). Chitinase is usually found in these organisms as it helps in reshaping their own cell wall. However, chitinase has been exploited by genetic engineering scientists and is used widely to digest fungal cell walls during DNA isolation.

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

  1. Plasmid DNA and Chromosomal DNA
  2. RNA and DNA
  3. Exonuclease and Endonuclease


a. Plasmid DNA and Chromosomal DNA

Plasmid DNA Chromosomal DNA
Plasmid DNA is an extra chromosomal DNA molecule separate from the chromosomal DNA and is capable of replicating independently of the chromosomal DNA. Chromosomal DNA acts as the genetic material of the cell. It is found in the cytosol of bacterial cell and in nucleus of eukaryotic cells. It is well organised and packed compactly with the help of histone proteins.
It is usually circular and double stranded. It is double stranded but not circular in eukaryotes.
It occurs naturally in bacteria and is sometimes also found in eukaryotes. It is found in all living cells.
It can be easily transferred from one cell to another without affecting the function of the host. Its transfer is not possible.

b. RNA and DNA

RNA is the genetic material of only RNA viruses. DNA is the genetic material of all living organisms.
A pyrimidine base called uracil (U) replaces thymine (T) in RNA. The four bases found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).
Sugar present in an RNA molecule is ribose. Sugar present in DNA is deoxyribose.
RNA can exist as a single molecule or a complex structure along with various proteins. DNA does not usually exist as a single molecule, but instead, it is present as a tightly-associated pair of molecules.
RNA molecules carry out various cellular functions mainly transcription and translation. DNA stores genetic information.

c. Exonuclease and Endonuclease

Exonuclease Endonuclease
Exonucleases are enzymes that cleave the nucleotides at the end of the DNA molecule. Endonucleases are enzymes that cleave the bonds of the DNA from within the molecule at a specific site.
The cleavage by exonuclease results in the formation of free nucleotides or nucleosides. The cleavage by endonuclease breaks the DNA molecule into two and also results in the formation of oligonucleotides.

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FAQs (Frequently Asked Questions)

1. Is Chapter 11 of Biology for Class 12 crucial for board exams?

Yes, Chapter 11 of Biology for Class 12 is crucial for passing the board exams. To get a perfect score, you must understand all the topics. Extramarks provides expert-created NCERT Solutions Class 12 Biology Chapter 11 for students to study and revise for their examinations. These questions will assist students in achieving a perfect score on their board exams.

2. What exactly does it mean when you read "origins of replication"?

A particular segment in a chromosome is responsible for starting replication, and this sequence is known as the “origin of replication.” To replicate any foreign DNA fragment that carries the gene of interest in an organism in biotechnology, the piece of DNA must be connected at the origin of replication, the region of the chromosome that includes that specific sequence of DNA. The alien DNA will only be able to replicate and increase in the host organism after that.