The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 12 Biology Chapter 11, "Biotechnology:Principles And Processes" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 12 Biology with others—learning is always better when shared!
QUESTIONS FROM TEXTBOOK SOLVED
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: Here is a list of 10 recombinant proteins used in medical practice, along with their therapeutic applications:
- Insulin - Used to treat diabetes, recombinant human insulin helps manage blood sugar levels in people with Type 1 and Type 2 diabetes.
- Erythropoietin (EPO) - Stimulates red blood cell production, used to treat anemia, particularly in chronic kidney disease and chemotherapy patients.
- Human Growth Hormone (HGH) - Used to treat growth disorders in children and growth hormone deficiency in adults.
- Interferon-alpha - Used to treat viral infections such as hepatitis B and C, as well as certain cancers like melanoma and lymphoma.
- Interferon-beta - Used in the treatment of multiple sclerosis (MS) to reduce the frequency of relapses.
- Factor VIII - A blood-clotting protein used to treat hemophilia A, a genetic disorder affecting the blood's ability to clot.
- Factor IX - Used for treating hemophilia B, helping patients manage clotting deficiencies.
- Granulocyte Colony-Stimulating Factor (G-CSF) - Stimulates the production of white blood cells, used in cancer patients to combat neutropenia after chemotherapy.
- Tissue Plasminogen Activator (tPA) - Used to treat ischemic stroke by dissolving blood clots that block blood flow to the brain.
- Recombinant Hepatitis B Vaccine - Protects against hepatitis B infection, commonly administered as part of childhood vaccination programs.
These recombinant proteins are produced using biotechnological methods and play a significant role in treating a variety of diseases, improving patient outcomes across the globe
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: Both DNA and enzymes are macromolecules. DNA is a polymer of deoxyribonucleotides and enzymes are proteins hence these are polymers of amino acids. But DNA is bigger in molecular size as compared to proteins because synthesis of proteins is regulated by a small segment of DNA, called genes and also a large number of proteins can be synthesized by a DNA molecule.
4. What would be the molar concentration of human DNA in a human cell? Consult your teacher.
Ans: To estimate the molar concentration of human DNA in a human cell, we need to consider several factors:
DNA content per cell: A typical human diploid cell has about 6.4 billion base pairs of DNA, corresponding to a genome size of approximately 6.4 gigabases.
Molecular weight of a base pair: The average molecular weight of a DNA base pair is around 650 Daltons.
Total DNA mass per cell: For a diploid human cell, the total mass of DNA can be calculated using the number of base pairs and the molecular weight of each base pair.
Since 1 Dalton = , the DNA mass in grams is:
- Volume of a cell: The typical volume of a human cell is about 1 picoliter ().
Molar concentration: To find the molar concentration, divide the number of moles of DNA by the volume of the cell:
Now, the molar concentration is:
Thus, the molar concentration of human DNA in a cell is approximately 0.01 M. This is a rough estimate and can vary depending on the assumptions made for cell volume and genome size.
5. Do eukaryotic cells have restriction endonucleases? Justify your answer.
Ans: No, eukaryotic cells do not have restriction endonuclease because DNA molecules of eukaryotes are heavily methylated. All the restriction endonucleases have been isolated from various strain of bacteria.
6. Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
Ans: The shake flask method is used for a small-scale production of biotechnological products in a laboratory. On the other hand, stirred tank bioreactors are used for a large-scale production of biotechnology products.
Stirred tank bioreactors have several advantages over shake flasks:
- Small volumes of culture can be taken out from the reactor for sampling or testing.
- It has a foam breaker for regulating the foam.
- It has a control system that regulates the temperature and pH.
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: Palindrome nucleotide sequences in the DNA molecule are groups of bases that form the same sequence when read both forward and backward. Five examples of palindromic DNA sequences are as follows:
(i) 5′-—————GGATCC——————3’
3′—————CCTAGG—————–5′
(ii) 5’—————AAGCTT——————3′
3′——————TTCGAA —————-5′
(iii) 5′—————–ACGCGT—————–3′
3′——————TGCGGA————– 5′
(iv) 5′———- ACTAGT————3′
3′——————TGATCA————5′
(v) 5′—————AGGCCT—————3′
3′——————TCCGGA————–5′
8. Can you recall meiosis and indicate at what stage a recombinant DNA is made?
Ans: Meiosis involves reduction in the number of genetic material. Meiosis is divided into two kinds: meiosis I and meiosis II. Prophase I of which the pachytene stage will consist of the cross over of chromosomes formation where the segments between non-sister chromatids of homlogous chromosomes take place to form a 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: Reporter gene: It can be utilized to monitor the host cells' transformation by foreign DNA. They act as a selectable marker to establish whether the host cell has taken up foreign DNA or whether the foreign gene gets expressed inside the cell. The researchers place the reporter gene and the foreign gene in the same DNA construct. This combined DNA construct is then inserted in the cell. Then, a reporter gene is used to act as a selectable marker in the differentiation of successful uptake of genes of interest.
For instance, a very good example of a reporter gene is the lac Z gene which encodes the green fluorescent protein from the jellyfish.
10. Describe briefly the followings:
(a) Origin of replication
(b) Bioreactors
(c) Downstream processing
Ans: (a) Origin of Replication: This is a sequence from where replication begins and any fragment of DNA when ligated to this sequence can be made to replicate within the host cells. This sequence also controls the copy number of the ligated DNA. Thus, if one wants to recover many copies of the target DNA it should be cloned in a vector whose origin support high copy number.
(b) Bioreactor: Bioreactors can be termed as vessels in which raw materials are biologically converted by microbes, plant and animal cell and/or their enzymes into specific products. The bioreactor provides optimum growth conditions and facilitates achieving the desired products. The most commonly used bioreactor is of stirring type. A stirred tank bioreactor is usually a cylindrical vessel or vessel with a curved base to facilitate mixing of the contents. Sterilized air bubbles are sparged in the sparged stirred tank bioreactor. The stirrer enables mixing and availability of oxygen in the bioreactor. An agitator system, an oxygen delivery system, a foam control system, a temperature control system, a pH control system, and sampling ports are found in a bioreactor.
(c) Downstream Processing : The product resulting from the upstream process is further exposed to a series of steps which are commonly called downstream processing to produce the final product ready for marketing. There are mainly two processes: separation and purification. The formulated product is then exposed to appropriate preservatives. Such formulations have to be tested in clinical trials, if the product happens to be a drug.
11. Explain briefly
(a) PCR
(b) Restriction enzymes and DNA
(c) Chitinase
Ans: (a) PCR: PCR stands for polymerase chain reaction, which is the technology in molecular biology to amplify a gene or a segment of DNA into several of its copies. It has become highly operative in the process of gene manipulation. The synthesis is carried out in-vitro using a primer, a template strand, and a thermostable DNA polymerase enzyme that is obtained from a bacterium called Thermus aquaticus. The lengthening occurs with the help of building blocks dNTPs (deoxynucleotides). First, double-stranded DNA molecules are heated to such a high temperature that the two strands separate into a single-stranded DNA molecule, which is called denaturation. The ssDNA molecule produced here acts as a template for the production of another new strand of nucleic acid, by DNA polymerase enzyme; this process is known as annealing, and it results in the duplication of the DNA molecule. This cycle is repeated several times to produce several copies of the rDNA fragment.
(b) Restriction enzymes and DNA: Restriction enzymes are molecular scissors that are used in molecular biology to cut DNA sequences from a specific site. It plays an important role in gene manipulation. The enzymes recognize a specific six-box pair sequence known as the recognition sequence and cut the sequence at a specific site. For example, the recognition site for enzyme ECORI is as follows
Restriction endonucleases are categorized into two:
(i) Exonuclease: This is a type of restriction enzyme that removes a nucleotide from either 3' or 5' ends of the DNA molecule.
(ii) Endonuclease: Such restriction enzymes cut the DNA within. The enzymes are a crucial tool in genetic engineering. They are generally used to cut a sequence to acquire fragments of DNA with sticky ends later joined by enzyme DNA ligase.
(c) Chitinase: Chitinases are a class of enzymes used for chitin degradation, which composes a considerable amount of the fungal cell wall. Therefore, to obtain DNA enclosed within the membrane of the fungal cell, enzyme chitinase is used to break up the cell for the release of its genetic material.
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 VS Chromosomal DNA
Plasmid DNA:
- Plasmids are small, circular, double-stranded DNA molecules.
- They exist independently of chromosomal DNA and are typically found in bacteria.
- Plasmids can replicate autonomously within the cell.
- They often carry genes that provide advantages such as antibiotic resistance but are not essential for basic survival.
- Plasmid DNA can be transferred between bacteria through horizontal gene transfer (conjugation).
Chromosomal DNA:
- Chromosomal DNA is larger and contains the organism’s essential genetic information required for growth, development, and reproduction.
- It is linear in eukaryotes (like humans) and circular in prokaryotes (like bacteria).
- Chromosomal DNA is organized into chromosomes, which undergo replication during cell division.
- It is inherited vertically from parent to offspring.
(b) RNA and DNA
RNA (Ribonucleic Acid):
- RNA is usually single-stranded.
- The sugar in RNA is ribose, which contains one more oxygen atom compared to deoxyribose in DNA.
- RNA contains the base uracil (U) instead of thymine (T) found in DNA.
- RNA plays multiple roles, including as a messenger (mRNA), part of the ribosome (rRNA), and in protein synthesis (tRNA).
- RNA is generally more unstable and has a shorter lifespan in the cell compared to DNA.
DNA (Deoxyribonucleic Acid):
- DNA is double-stranded and forms a helical structure.
- It contains deoxyribose as its sugar, which lacks an oxygen atom compared to ribose in RNA.
- DNA contains the base thymine (T) instead of uracil (U).
- DNA serves as the permanent genetic blueprint for an organism, storing all genetic information.
- It is more stable than RNA and lasts much longer in the cell.\
(c) Exonuclease and Endonuclease
Exonuclease:
- Exonucleases remove nucleotides one at a time from the ends of a DNA or RNA strand.
- They can act on either the 5’ end or the 3’ end of the nucleic acid.
- Exonucleases are often involved in DNA repair, replication, and the degradation of defective or excess DNA/RNA.
Endonuclease:
- Endonucleases cut within the DNA or RNA strand by breaking the phosphodiester bonds at specific internal sites.
- They play crucial roles in processes like restriction (where restriction enzymes cut DNA at specific sequences) and DNA repair.
- A well-known example of an endonuclease is the restriction enzyme EcoRI, which cuts DNA at a specific palindromic sequence.
