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

SimplyAcad has brought the solved NCERT Solutions for Chapter 9 Biotechnology Principles and Processes Class 12 so students can start preparing as soon as possible for their approaching 12th Board examination. The solutions aim to benefit students the most through the conceptual ideas presented in a detailed way. These will ensure students grasp the basic concepts tightly and answer their papers with confidence.

Biotechnology is an essential multidisciplinary field involving the combination of technology and natural science for various research and experimentations. The section includes a broad spectrum of approaches attracting most researchers and engineers. 

Our subject experts have prepared the answers according to the recent CBSE Syllabus of 2024-25. Students can easily access them by scrolling below. 

Biotechnology Principles and Processes Class 12 Biology Chapter 9 Questions 1 to 4

Question 1

Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics.

Solution:

The recombinant proteins used in medical practice are obtained from recombinant DNA technology. In this technology, particular genes are transferred from one organism to another with the help of vectors and restriction enzymes as molecular tools.

Listed below are 10 recombinant proteins:

Recombinant Protein	Therapeutic Application
Interferon-α	In the treatment of chronic hepatitis C
Insulin	In the treatment of type I diabetes mellitus
Interferon-β	Used to treat herpes and viral enteritis
Interferon B	In the treatment of Multiple Sclerosis
Anti-thrombin III	Blood clot prevention
Human recombinant growth hormone	To promote growth in individuals
Coagulation factor VIII	In the treatment of hemophilia A
Coagulation factor IX	In the treatment of hemophilia B
DNAase I	In the treatment of cystic fibrosis
Tissue plasminogen activator	In the treatment of acute myocardial infarction

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Question 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.

Solution:

Steps in the formation of recombinant DNA by the action of the restriction endonuclease enzyme – EcoRI.

It can be diagrammatically represented as follows:

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Question 3

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

Solution:

Compared to DNA molecules, enzymes are smaller in size. This is evident because DNA comprises the genetic material essential for the normal development and functioning of living entities. A DNA molecule consists of instructions required for the synthesis of DNA molecules and proteins. Enzymes, on the other hand, are proteins synthesized from genes—a small fragment of DNA. These enzymes are crucial in the production of the polypeptide chain.

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Question 4

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

Solution:

The molar concentration of human DNA in a human cell can be given as:

$\text{Molar Concentration} = 6.023 \times 10^{23} \times \text{Total number of chromosomes}$ $= 6.023 \times 10^{23} \times 46$ $= 2.77 \times 10^{23} \text{ moles}$

Therefore, the molar concentration of DNA in each of the diploid cells in humans is 2.77 x 10^23 moles.

Biotechnology Principles and Processes Class 12 Biology Chapter 9 Questions 5 to 8

Question 5

Do eukaryotic cells have restriction endonucleases? Justify your answer.

Solution:

No, eukaryotic cells do not have restriction endonucleases, as the DNA of eukaryotes is highly methylated by methylase—a modification enzyme. This methylation safeguards the DNA from the action of restriction enzymes. In prokaryotic cells, these enzymes are present and aid in preventing the invasion of DNA by viruses.

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Question 6

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

Solution:

Stirred tank bioreactors are developed for the large-scale production of biotechnology products, whereas the shake flask method is applied for the small-scale production of biotechnological products carried out in a laboratory.

The stirred tank bioreactor has a few advantages over shake flasks:

(i) Small amounts of culture can be drawn out from the reactor for testing and sampling.

(ii) It has a control system to regulate pH and temperature.

(iii) Stirred tank bioreactors have a foam breaker to regulate foam.

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Question 7

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

Solution:

A sequence of DNA that reads the same whether read from 5’ -> 3’ or from 3’ -> 5’ direction is a palindromic sequence. These are the sites for the action of restriction enzymes. Almost all restriction enzymes act on palindromic sequences.

Listed below are 5 examples of palindromic sequences:

1. 5′ GGATCC 3′ ——— 3′ CCTAGG 5′
2. 5′ AAGCTT 3′ ——— 3′ TTCGAA 5′
3. 5′ ACGCGT 3′ ——— 3′ TGCGCA 5′
4. 5′ ACTAGT 3′ ——— 3′ TGATCA 5′
5. 5′ AGGCCT 3′ ——— 3′ TCCGGA 5′

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Question 8

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

Solution:

Meiosis is a type of cell division that involves a reduction in the quantity of genetic material. It occurs in two phases, namely meiosis I and meiosis II.

In the pachytene event of prophase I, chromosomes cross over, during which the exchange of segments between non-sister chromatids of homologous chromosomes occurs. This leads to the formation of recombinant DNA in the process of meiosis.

Biotechnology Principles and Processes Class 12 Biology Chapter 9 Questions 9 to 12

Question 9

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

Solution:

A reporter gene can be used to monitor the transformation of host cells by foreign DNA. It serves as a selectable marker to determine if the host cell has incorporated the foreign DNA or if the foreign gene is expressed in the cell. Scientists place the reporter gene and the foreign gene in the same DNA construct. This collective DNA construct is introduced into the cell, where the reporter gene acts as a selectable marker to discover the successful uptake of foreign genes or the genes of interest. The lac Z gene, which encodes for a green fluorescent protein in jellyfish, is an example of a reporter gene.

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Question 10

Describe briefly the following:

(a) Origin of replication
(b) Bioreactors
(c) Downstream processing

Solution:

(a) Origin of replication

The origin of replication is a DNA sequence in a genome where replication is initiated. The process of replication initiation can either be uni-directional or bi-directional. Any piece of DNA linked to this sequence can be made to replicate within host cells. The sequence also controls the copy number of the linked DNA. To recover many copies of target DNA, it should be cloned in a vector whose origin supports a high copy number.

(b) Bioreactor

Bioreactors are large vessels used for the large-scale production of biotechnological products from raw resources. These bioreactors offer optimal conditions by supplying the required pH, temperature, vitamins, oxygen, etc., to obtain the desired product. They have an oxygen delivery system, a foam control system, and a temperature and pH control system. Additionally, they consist of a sampling port to withdraw small quantities of culture for testing.

(c) Downstream processing

Downstream processing is the method of separating and purifying foreign gene products once the biosynthetic stage is completed. The product is then exposed to different procedures to separate and purify it. Once the process is completed, the product is formulated and subjected to several clinical trials for quality checks and other related assessments.

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Question 11

Explain briefly:

(a) PCR
(b) Restriction enzymes and DNA
(c) Chitinase

Solution:

(a) PCR

Polymerase Chain Reaction (PCR) is a technique used in molecular biology to amplify a gene or a fragment of DNA to obtain multiple copies. It is widely used in gene manipulation processes. PCR involves the in vitro synthesis of sequences using a template strand, a primer, and a thermostable DNA polymerase enzyme produced by a bacterium known as Thermus aquaticus. The enzyme uses deoxynucleotides (dNTPs) to extend the primer.

The three steps in PCR are:

(i) Denaturation: The double-stranded DNA molecules are heated to a high temperature to separate them into single-stranded DNA molecules.

(ii) Annealing: The DNA molecule is used as a template strand to synthesize a new strand by the DNA polymerase enzyme, leading to the replication of the original DNA molecule.

(iii) Extension: The primer is extended by Taq DNA polymerase isolated from Thermus aquaticus.

(b) Restriction enzymes and DNA

In molecular biology, restriction enzymes are molecular scissors used to cut DNA sequences at specific sites. These enzymes play a critical role in gene manipulation processes. They identify a specific six-base pair sequence, referred to as the recognition sequence, and snip the sequence at particular sites. For example, the recognition site for the EcoRI enzyme is:

Restriction enzymes are grouped into two types:

(i) Endonuclease: This restriction enzyme cuts within the DNA at specific sites, producing sticky ends. These ends are later fused by the enzyme DNA ligase.

(ii) Exonuclease: This restriction enzyme removes nucleotides either from the 3’ or 5’ ends of the DNA molecule.

(c) Chitinase

Chitinase is a class of enzymes used to degrade chitin, the main component of the cell wall of fungi. To isolate the DNA within the cell membrane of the fungus, the chitinase enzyme is used to break the cell and release its genetic material.

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Question 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

Solution:

(a) Plasmid DNA and Chromosomal DNA

Plasmid DNA	Chromosomal DNA
An extra-chromosomal DNA molecule found in bacteria, capable of replicating independently of chromosomal DNA.	Forms the complete DNA of an organism, found inside chromosomes.

(b) RNA and DNA

RNA	DNA
Single-stranded molecule	Double-stranded molecule
Cannot replicate by themselves	Can replicate
Consists of ribose sugar	Consists of deoxyribose sugar
Pyrimidines are uracil and adenine	Pyrimidines are thymine and adenine
Component of ribosomes	Component of chromosomes

(c) Exonuclease and Endonuclease

Exonuclease	Endonuclease
Removes nucleotides from the 5’ or 3’ terminals of the DNA molecule.	Snips within the DNA at specific sites to produce sticky ends.