Find Class 12 Biology Chapter 9 Biotechnology Principles and Processes Question Answer
Given below are the detailed answers to all the questions given in the textbook. Class 12 Biology Chapter 9 Biotechnology Principles and Processes question answers are prepared according to the latest NCERT guidelines, which provide knowledge about how biotechnology has changed our lives.
Q1. Can you list 10 recombinant proteins that are used in medical practice? Find out where they are used as therapeutics (use the internet).
Answer:
Recombinant proteins are proteins produced as a result of recombinant DNA technology. In this technology, there is the transfer of a specific gene from one organism to another by using molecular tools such as biological vectors, restriction enzymes, etc. Some of the proteins produced through RDT and are being used for therapeutic uses are as follows:
S.No | Name of the recombinant protein | Therapeutic use of the recombinant protein |
1. | DNase I | To treat cystic fibrosis |
2. | Antithrombin III | To prevent the formation of blood clots |
3. | Insulin | To treat type I diabetes mellitus |
4. | Interferon α | Used for chronic hepatitis C |
5. | Coagulation factor VIII | To treat hemophilia A |
6. | Coagulation factor IX | To treat hemophilia B |
7. | Interferon-β | To treat multiple sclerosis |
8. | Recombinant Human Growth Hormone (rhGH) | To promote growth in humans |
9. | Tissue plasminogen activator | To treat the myocardial infarction |
| 10. | Erythropoietin (EPO) | To treat anemia in chronic kidney disease and chemotherapy patients |
Q2. 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
Answer:
The following chart shows the action of the restriction enzyme EcoRI, the substrate DNA on which it acts, and the site where it cuts
Q3. From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
Answer:
DNA possesses all the genetic information of an organism. This genetic information can be transcribed into the form of proteins, multiprotein complexes, enzymes, etc. The actual length of DNA is in meters. The actual size of DNA is 2 meters long. Although they are present in condensed form. So they appear smaller when compared to enzymes. While enzymes, on the other hand, have variable sizes but are only a few nanometers in length. Hence, they will always be smaller when compared to DNA. Thus, we can conclude that DNA is bigger than enzymes.
Q4. What would be the molar concentration of human DNA in a human cell? Consult your teacher.
Answer:
The molar concentration of DNA in a human cell will be the total no. of chromosomes divided by 6.023 × 1023
Hence, the molar concentration of DNA in each diploid cell in humans is 46/6.023 × 1023 = 7.64 × 10-23
Q5. Do eukaryotic cells have restriction endonucleases? Justify your answer.
Answer:
No, eukaryotic cells do not have bacterial-type restriction endonucleases. Restriction endonucleases have been isolated from bacteria, where they act as a defense mechanism against invading viruses. Bacteria protect their own DNA from cleavage by methylation. Eukaryotes, instead, use different defense strategies such as nucleases, DNA methylation/repair systems, and RNA interference (which mainly targets viral RNA).
Q6. Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
Answer:
The advantages of stirred tank bioreactors over shake flasks are as follows:
1. Stirred tank bioreactors are utilized for large-scale production of biotechnological products, unlike the shake flask method, which is used for small-scale production of products.
2. In stirred tank bioreactors, a small sample can be taken out for testing.
3. Stirred tank bioreactors have foam breakers to control the foam.
4. Stirred tank bioreactors have temperature and pH control systems.
Q7. Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following the base-pair rule
Answer:
Palindromic sequences in the DNA molecule refer to groups of bases forming the same sequence when read either backward or forward. The recognition sites of restriction endonucleases are palindromic sequences. Five examples of palindromic DNA sequences are given below
1. ACTAGT/TGATCA
2. AAGCTT/TTCGAA
3. GGATCC/CCTAGG
4. AGGCCT/TCCGGA
5. ACGCGT/TGCGCA
Q8. Can you recall meiosis and indicate at what stage a recombinant DNA is made?
Answer:
In meiosis, during the pachytene stage of Prophase I, crossing-over takes place and recombinant DNA is formed by combining portions of male and female DNA.
Q9. 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?
Answer:
In recombinant DNA technology, the selection of transformed and non-transformed cells can be done using reporter genes that encode reporter enzymes. During the RDT experiment, the foreign gene is joined with a reporter gene. The reporter gene should be such that it produces a visible expression. For example, the Lac Z gene, which codes for the enzyme beta-galactosidase, is used as a reporter gene. The activity of this gene is not found in transformed cells, as the product formed by its catalysis is not formed in transformed cells, and bacterial colonies appear white. In non-transformed cells, this gene shows its activity, and the catalyzed product is formed; as a result of this, bacterial colonies appear blue. Thus, a reporter enzyme can be used to monitor the transformation of host cells by foreign DNA in addition to a selectable marker.
Q10. Describe briefly the following:
(a) Origin of replication
Answer:
Origin of replication- This refers to the DNA sequence from which replication of DNA starts. By linking a DNA sequence with the origin of replication, it can be allowed to replicate in the host cells. The origin of replication also controls the copy number of linked DNA sequences.
(b) Bioreactor
Answer:
Bioreactors - These are vessels used for large-scale production of biotechnological products such as proteins, enzymes, etc., from raw materials. They can range from small laboratory fermenters (a few liters) to large industrial bioreactors (thousands of liters). In a bioreactor, optimum conditions such as temperature, pH, vitamins, oxygen, and salts are maintained. Stirred tank bioreactors are the most commonly used types, either as simple stirred tanks or sparged tanks.
(c) Downstream processing
Answer:
Downstream processing- The process of separation and purification of biotechnological products is called downstream processing. The processes in downstream processing vary depending on the quality of the product. Before the release of the product, it undergoes clinical trials and quality control testing.
Q11. Explain briefly :
(a) PCR
Answer:
Polymerase Chain Reaction (PCR)- The molecular technique to amplify a gene and obtain several copies is referred to as PCR. The process of PCR has certain requirements, i.e., a thermostable enzyme called Taq polymerase ( obtained from Thermus aquaticus ), primers ( short stretches of DNA ), dNTPs, a template strand, etc. The process of PCR takes place in three steps.
1. Denaturation- The double-stranded DNA helix is opened up by breaking its H-bonds at high temperatures.
2. Annealing- The primers are allowed to hybridize to complementary regions of DNA. This step takes place at a 50-65°C temperature.
3. Extension- The primers are extended with the help of the Taq polymerase enzyme, and the cycle is repeated several times to obtain the desired number of copies.
(b) Restriction enzymes and DNA
Answer:
Restriction enzymes and DNA- Restriction enzymes are those enzymes that cut DNA at particular places. The restriction enzyme first scans the DNA template and looks for its recognition site. Once it finds the recognition site, it binds at that region of DNA and cuts each of the two strands in its sugar-phosphate backbone. The sites at which restriction enzymes cut DNA are called recognition sites of DNA. These are palindromic sequences, i.e., they read similarly from the backward and forward direction.
(c) Chitinase
Answer:
Chitinase - The enzyme that catalyzes the breakdown of chitin polysaccharide, which is usually found in the cell wall of fungi. Chitinase is mainly used during DNA isolation from fungi.
Q12. Discuss with your teacher and find out how to distinguish between
(a) Plasmid DNA and Chromosomal DNA
Answer:
The differences between plasmid DNA and chromosomal DNA are as follows:
Plasmid DNA | Chromosomal DNA |
Circular, extra-chromosomal DNA capable of self-replication, found commonly in bacteria and archaea, also in some eukaryotes (e.g., yeast). | The entire genomic DNA of the cell (excluding extrachromosomal DNA) is present as chromosomes. |
Usually small in size and often present in multiple copies. | Larger in size, usually present as one or more copies, depending on the organism. |
| Used as vectors in genetic engineering. | Contains most of the genetic information essential for survival. |
(b) RNA and DNA
Answer:
The differences between RNA and DNA are as follows:
RNA | DNA |
RNA contains ribose sugar | DNA contains the deoxyribose sugar |
Has bases adenine (A), guanine (G), cytosine (C), and uracil (U) | Has bases adenine (A), guanine (G), cytosine (C), and thymine (T) |
It has catalytic properties and is less stable than DNA | DNA is non-catalytic and is more stable than RNA |
(c) Exonuclease and Endonuclease
Answer:
The differences between exonuclease and endonuclease are as follows:
Exonuclease | Endonuclease |
These are nucleases (enzymes) that cut DNA from its ends. | These are nucleases that cut DNA from internal sites on DNA |
NCERT Solutions for Class 12- Subject-wise
Important Questions of NCERT Class 12 Biology Chapter 9 Biotechnology Principles and Processes
Given below are some of the important questions from this chapter, along with the answer. This helps students understand how the question appeared in the exam. To practice more such types of questions, students can refer to the NCERT Solutions for Class 12 Biology Chapter 9 Biotechnology Principles and Processes.
Question 1: Among the following statements, carefully identify the ones that contain incorrect information about the palindromic sequences.
A. Palindromic sequences are DNA sequences that read the same in both directions but have an antiparallel orientation.
B. Palindromic sequences are DNA sequences that read the same in both directions but have a parallel orientation.
C. Palindromic sequences are recognized by a specific restriction endonuclease, leading to specific cleavage.
D. Palindromic sequences are recognized by exonucleases, resulting in non-specific cleavage.
Choose the option(s) that contain incorrect statements:
Options:
A and C
A and D
B and C
B and D
Answer: The correct answer is option (4).
Explanation:
Statement B states that the Palindromic sequences are DNA sequences that read the same in both directions but have a parallel orientation. This statement is incorrect. Palindromic sequences have an antiparallel orientation, not a parallel one. Therefore, statement B is incorrect.
Statement D states that the palindromic sequences are recognized by exonucleases, resulting in non-specific cleavage. This statement is incorrect. Exonucleases degrade DNA from the ends, but they do not specifically recognize and cleave palindromic sequences. Therefore, statement D is incorrect.
Hence, the correct statements are B and D.
Question 2: Which of the following should be chosen for the best yield if one were to produce a recombinant protein in large amounts?
Laboratory flask of the largest capacity
A stirred-tank bioreactor without inlets and outlets
A continuous culture system
Any of the above
Answer: The correct answer is option (3).
Explanation:
A large flask, without a suitable culture system, is not going to yield anything. The same holds true for a tank bioreactor. It is the continuous culture system that is a must for producing a recombinant protein.
Question 3: Which of the following statements does not hold for a restriction enzyme?
It recognizes a palindromic nucleotide sequence
It is an endonuclease
It is isolated from viruses
It can produce the same kind of sticky ends in different DNA molecules
Answer: The correct answer is option (3).
Explanation:
Restriction enzymes are obtained from certain bacteria, not viruses. They act as endonucleases that recognize specific palindromic DNA sequences and cut them at defined sites. Hence, the statement “It is isolated from viruses” is incorrect.
Question 4: The role of DNA ligase in the construction of a recombinant DNA molecule is:
Formation of a phosphodiester bond between two DNA fragments
Formation of hydrogen bonds between sticky ends of DNA fragments
Ligation of all purine and pyrimidine bases
None of the above
Answer: The correct answer is option (1).
Explanation:
The correct answer is option (1), Phosphodiester bond formation between two DNA fragments. DNA ligase is an enzyme that forms a phosphodiester bond between two DNA fragments. This is the most significant role for DNA ligase during the processes of DNA replication and repair, as well as in recombinant DNA technology, when it is required to ligate the ends of DNA molecules with sticky ends or blunt ends.
Question 5: An antibiotic resistance gene in a vector usually helps in the selection of:
Competent bacterial cells
Transformed bacterial cells
Recombinant bacterial cells
None of the above
Answer: The correct answer is option (2).
Explanation:
In the process of culturing cells, only those that have been successfully transformed will thrive on the agar plate. These specialized cells possess a unique resistance to antibiotics, allowing them to survive in an otherwise lethal environment. As a result, they can be easily identified based on their ability to grow despite the presence of these antimicrobial agents.
Question 6: Which of the following is essential for introducing recombinant DNA into a host cell?
- Bioreactor
- Vector
- Chromatography
- Electrophoresis
Answer: The correct answer is option (2).
Explanation:
A vector, such as a plasmid or bacteriophage, carries the recombinant DNA into the host cell. It ensures replication, expression, and stable maintenance of the inserted gene.
Question 7: In gel electrophoresis, DNA fragments are separated primarily on the basis of:
- Colour
- Solubility
- Charge and size
- pH
Answer: The correct answer is option (3).
Explanation:
DNA fragments move through agarose gel based on their negative charge and molecular size. Smaller fragments travel faster and farther than larger ones toward the positive electrode.
Question 8: Which of the following enzymes is used to cut DNA at specific recognition sites?
- DNA polymerase
- RNA polymerase
- Restriction endonuclease
- DNA ligase
Answer: The correct answer is option (3).
Explanation:
Restriction endonucleases recognize specific palindromic DNA sequences and cleave the DNA at defined positions. This property is essential for gene cloning and recombinant DNA technology.
Question 9: Which of the following is used as a selectable marker in cloning vectors?
- Origin of replication
- Restriction site
- Antibiotic resistance gene
- Promoter
Answer: The correct answer is option (3)
Explanation:
Selectable marker genes, such as antibiotic resistance genes, help identify and select host cells that have successfully taken up the recombinant DNA, as only transformed cells survive in the presence of the antibiotic.
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