CBSE Class 12 – Biotechnology Question Paper 2023

 

SECTION A

1. Blue-White selection technique of transformants is based on insertional inactivation of:
(a) Leu2 gene
(b) LacZ gene
(c) X-gal gene
(d) Tet-r gene

Answer:
(b) LacZ gene

2. Microbial source of Hind III restriction enzyme is:
(a) Haemophilus aegyptius
(b) Haemophilus influenzae
(c) Haemophilus haemolyticus
(d) Haemophilus felis

Answer:
(b) Haemophilus influenzae

3. Which of the following statement is not correct about DNA sequencing by Sanger Method?
(a) Primers can only be extended using the single strand DNA as template.
(b) Four ddNTPs ddATP, ddUTP, ddCTP and ddGTP are needed.
(c) DNA polymerase enzyme is needed.
(d) ddNTPs are added to terminate chain (DNA) extending.

Answer:
(b) Four ddNTPs ddATP, ddUTP, ddCTP and ddGTP are needed.
Correct answer: ddTTP is required instead of ddUTP.

4. Charge relay system operating in chymotrypsin enzyme consists of following amino acids at positions 57, 102 and 195 respectively:
(a) his-asp-ser
(b) his-lys-ser
(c) his-lys-asp
(d) lys-his-ser

Answer:
(a) his-asp-ser

5. Number of predicted genes is 6340 and 70% part of the genome codes for protein in:
(a) Yeast
(b) Caenorhabditis worm
(c) Arabidopsis weed
(d) Bacterium E. coli

Answer:
(d) Bacterium E. coli

6. SCID disease is caused by absence of enzyme:
(a) Adenosine synthase
(b) Adenosine deaminase
(c) Adenosine phosphatase
(d) Adenosine aminase

Answer:
(b) Adenosine deaminase

7. Technique of introducing colours into DNA by Nick Translation, was developed by:
(a) Rigby and Paul Berg
(b) Rous and Jones
(c) Kary Mullis and Paul Berg
(d) Edward Sanger

Answer:
(a) Rigby and Paul Berg

8. Alcaligenes eutrophus is associated with the production of:
(a) Streptomycin
(b) Penicillin
(c) Hepatitis antigen
(d) Poly 3-hydroxybutyrate

Answer:
(d) Poly 3-hydroxybutyrate

9. Expression vector has which of the following properties?
(a) High copy number and stable
(b) Easy to transfer in eukaryote cells
(c) Maximise production of foreign protein
(d) Both (a) and (c)

Answer:
(d) Both (a) and (c)

10. Artemisin obtained from Artemisia species is used as:
(a) Antimalarial
(b) Antifertility
(c) Anticarcinogenic
(d) Analgesic

Answer:
(a) Antimalarial

11. Transgenic plants which over-express compounds like sugars, mannitol, and proline:
(a) are pest resistant
(b) are abiotic stress tolerant
(c) produce more secondary metabolites as drugs and other important metabolites
(d) are weedicide tolerant

Answer:
(b) are abiotic stress tolerant

12. Person who lacks the ability to produce Factor VIII has heritable genetic disorder:
(a) Haemophilia A
(b) Haemophilia B
(c) Christmas disease
(d) Stroke

Answer:
(a) Haemophilia A

Haemophilia A is a genetic disorder caused by the deficiency or absence of Factor VIII, a blood-clotting protein.

Questions No. 13 to 16 consists of two statements Assertion (A) and Reason (R).
Answer these questions selecting the appropriate option given below : (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the
correct explanation of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not
the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

13. Assertion (A): Protoplasts are plant cells without cell wall.
Reason (R): Protoplasts can be utilized for producing somatic hybrids.

Answer:
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Explanation: Protoplasts are plant cells without cell walls, and they can indeed be used in the production of somatic hybrids through fusion techniques.

14. Assertion (A): Homology is defined as similarity due to common ancestry.
Reason (R): DNA sequences obtained from different individuals of same species show homology due to similarity in DNA sequence.

Answer:
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Explanation: Homology is defined as similarity due to common ancestry, but the similarity in DNA sequences within the same species doesn’t necessarily indicate homology. It can be due to conserved functions or genetic variation within species.

15. Assertion (A): Insert and vector DNA are cut with the help of Restriction endonuclease.
Reason (R): Ligase can produce the nick in the recombinant DNA molecule.

Answer:
(c) Assertion (A) is true, but Reason (R) is false.
Explanation: Restriction endonuclease cuts the DNA, but ligase actually seals the DNA fragments (not produce a nick). Reason (R) is incorrect because ligase joins the ends of DNA, whereas a nick refers to an unsealed break in the DNA strand.

16. Assertion (A): For the expression of eukaryotic proteins, E. coli is preferred.
Reason (R): E. coli is easy to grow and manipulate, so is used to express eukaryotic proteins.

Answer:
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Explanation: E. coli is often used for expressing proteins due to ease of growth and manipulation, but the primary challenge in using E. coli for eukaryotic proteins is the lack of post-translational modifications, which some eukaryotic systems provide.

SECTION B

17. (a) For selection of recombinants having lacZ gene on vector DNA, it was plated on medium containing sucrose with a chromogen dye. No result was obtained. Why?

Answer:
The lacZ gene may have been disrupted by the insertion, preventing β-galactosidase activity and no color formation.

(b) What can be done to select these recombinants?

Answer:
Use Blue-White selection method. White colonies indicate the presence of an insert disrupting lacZ.

18. How does mosquito repellent work? Mention its major chemical constituents.

Answer:
Mosquito repellents mask the odors mosquitoes are attracted to. DEET, Picaridin, and Citronella are common ingredients.

19. 6 million to 32 million sites in the human genome, where SNPs can occur, but still they may or may not affect gene function. Justify the statement giving reasons.

Answer:
SNPs often occur in non-coding regions or cause silent mutations that do not affect gene function or protein structure.

20. (a) Differentiate between Primary cell cultures and Secondary cell cultures.

Answer:

Feature Primary Cell Culture Secondary Cell Culture
Source Directly from tissues/organs Derived from primary cultures
Lifespan Limited Can grow for many passages
Growth rate Slower Faster
Use In vivo-like experiments Generalized or production use

OR

(b) Differentiate between Finite cell lines and Continuous cell lines.

Answer:

Feature Finite Cell Lines Continuous Cell Lines
Lifespan Limited Immortal (divides indefinitely)
Source Normal tissue Transformed or cancerous cells
Growth rate Slower Rapid growth
Use Closer to in vivo studies Large-scale production

21. How will you perform laboratory screening for microorganisms producing an antibiotic?

Answer:
Inoculate microorganisms on agar plates, streak test bacteria, and look for zones of inhibition around colonies indicating antibiotic production.

SECTION C

22. Give reason for the following:

(a) Baffle flasks have V-shaped notch.
Answer:
Baffle flasks have V-shaped notches to promote better mixing and aeration. The notches create turbulence, increasing the surface area for gas exchange and improving the oxygen transfer rate.

(b) Excess foaming in microbiological processes is a problem.
Answer:
Excess foaming can lead to loss of valuable culture, contamination, or overflow of the bioreactor. It also reduces oxygen transfer efficiency and can cause difficulties in maintaining proper culture conditions.

(c) Slaughter-house wastes are used to prepare media for microbiological processes.
Answer:
Slaughter-house wastes are rich in nutrients like amino acids, vitamins, and minerals, making them suitable for preparing microbiological media. They are an inexpensive and effective source of nutrients for microbial growth.

23. (a) How are mouse models created? Write two major applications in the field of stem cell technology.

Answer:

Creation of Mouse Models:

  1. Gene Knockout Models: A gene of interest is targeted, and its function is disrupted through genetic manipulation, often using CRISPR or homologous recombination techniques.
  2. Transgenic Models: Foreign DNA is injected into a mouse embryo to create a transgenic mouse with the desired genetic modification, typically for studying gene expression or disease models.

Two Major Applications of Stem Cell Technology:

  1. Regenerative Medicine: Stem cells are used to repair or replace damaged tissues and organs, such as in treating heart disease or spinal cord injuries.
  2. Disease Modeling and Drug Testing: Stem cells are used to create models of diseases, such as Alzheimer’s, to study disease mechanisms and test potential drug therapies.

OR

23. (b) Complete the flowchart for creating gene knockout by filling A, B, and C.

Answer:

  1. Selection of a gene of interest for knockout
  2. Place in plasmid
  3. Inject plasmid into A: Embryonic Stem (ES) Cells
  4. Homologous recombination
  5. Selection with B: Antibiotic resistance marker or other selective marker
  6. Injecting it into C: Blastocyst of a mouse embryo

(b) What is BLAST? What are the principles involved in this search program?

Answer:

BLAST (Basic Local Alignment Search Tool) is a bioinformatics algorithm used to compare an input sequence (DNA, RNA, or protein) against a database of sequences to find regions of similarity. It helps identify homologous sequences, infer functional relationships, and discover evolutionary patterns.

Principles Involved in BLAST:

  1. Query Sequence Comparison: BLAST compares a query sequence (DNA, RNA, or protein) against a sequence database to find similar or identical sequences.
  2. Heuristic Search: It uses heuristics, which are shortcuts to speed up the search process, instead of comparing all possible sequence combinations. This makes BLAST faster and more efficient than exhaustive methods.
  3. Word Matching: It divides the query sequence into short “words” (typically 3 for proteins or 11 for DNA), then searches the database for matching words. Only sequences with similar words are further analyzed.
  4. E-value (Expect Value): It calculates the likelihood of obtaining a match by chance. A lower E-value indicates a more significant match.
  5. Alignment Scoring: It uses scoring systems (such as match, mismatch, and gap penalties) to evaluate the similarity between sequences and provide alignment scores, which indicate how well sequences align.

24. Pichia pastoris is the most suitable host to express eukaryotic genes. Support the statement by giving three reasons.

Answer:

  1. Post-translational Modifications: Pichia pastoris can perform eukaryotic post-translational modifications, such as glycosylation, which is essential for the proper function of many eukaryotic proteins.
  2. High-Yield Production: Pichia pastoris can grow to very high cell densities, leading to high yields of recombinant proteins.
  3. Ease of Genetic Manipulation: It is genetically tractable and has well-established methods for transformation and expression of recombinant genes, making it a preferred choice for protein production.

25. Transgenic crops are facing challenges globally. What are the major concerns about these GM crops?

Answer:

  1. Environmental Impact: There are concerns about the unintended spread of genetically modified traits to wild relatives or non-GM crops through cross-pollination, potentially leading to loss of biodiversity.
  2. Health Risks: Potential long-term health effects of consuming genetically modified crops, such as allergenicity or toxicity, have raised concerns.
  3. Ethical and Socioeconomic Issues: Ethical concerns about altering the genetic makeup of organisms, and socioeconomic issues related to corporate control over GM seeds and their associated costs, have been significant concerns.

26. (a) Among all the biomolecules, proteins have maximum diversity in function. Why?

Answer:
Proteins have maximum functional diversity because they have complex three-dimensional structures that allow them to perform a wide variety of tasks, such as enzymatic catalysis, signaling, immune responses, and structural support.

(b) Proteome of a given cell is dynamic. Why?

Answer:
The proteome is dynamic because the protein content of a cell can change in response to environmental factors, stress, or changes in gene expression, resulting in continuous variation in the types and amounts of proteins present in the cell.

(c) m-RNA and protein expression levels in a cell do not always correlate. Why?

Answer:
mRNA and protein expression levels do not always correlate because protein synthesis and stability can be regulated independently of mRNA levels. Post-transcriptional regulation, such as translation efficiency and protein degradation, can influence protein abundance regardless of mRNA levels.

27. How is MALDI (Matrix Assisted Laser Desorption Ionisation) used to volatilize and protonate peptides and proteins?

Answer:
In MALDI, a sample (peptides/proteins) is mixed with a matrix substance, which absorbs laser energy. When the laser is applied, the matrix helps to volatilize (turn into gas) the peptides or proteins and protonate them. This ionization process generates charged particles (ions), which can then be analyzed by mass spectrometry to determine their molecular mass.

28. (a) What are the essential features that a vector should possess?

Answer:

  1. Origin of Replication (ORI): Ensures that the vector can replicate within the host cell.
  2. Selectable Marker: Allows for the identification of cells that contain the vector, often through antibiotic resistance.
  3. Cloning Site: A region where foreign DNA can be inserted for further manipulation or expression.
  4. Promoter Region: Drives the expression of the inserted gene in the host cell.

(b) What are shuttle vectors?

Answer:
Shuttle vectors are plasmid vectors that are designed to replicate in more than one host organism (e.g., both in prokaryotic and eukaryotic cells). They contain elements that allow them to function in different host systems, facilitating gene expression and manipulation in a variety of organisms.

SECTION D

29. (a) Read the passage and answer the question that follows:

Passage:
Single nucleotide polymorphisms (SNPs) are common genetic variations among people. Each SNP represents a difference in a single nucleotide and normally occur throughout a person’s DNA. SNPs can help scientists to locate genes associated with disease. Research is going on to identify SNPs associated with diseases like diabetes, cancer, etc.

(i) How can SNPs help physicians?

Answer:
SNPs can help physicians by allowing them to identify genetic variations associated with specific diseases, such as diabetes or cancer. This can aid in early diagnosis, personalized treatment plans, and predicting a patient’s response to medications.

(ii) SNPs can decide our susceptibility to, or protection from all kinds of diseases. Give any one example to support the same.

Answer:
One example is the SNP associated with the gene APOE in Alzheimer’s disease. Certain SNPs in the APOE gene can increase susceptibility to Alzheimer’s, while others may offer protection from the disease.

(iii) Why is SNP analysis used in population genetics?

Answer:
SNP analysis is used in population genetics to study genetic diversity, identify genetic markers for specific traits or diseases, trace human migration patterns, and understand how genetic variations are distributed across populations.

OR

(iii) Do SNPs occur only in coding regions of the human genome or in both coding and non-coding regions?

Answer:
SNPs occur in both coding and non-coding regions of the human genome. While SNPs in coding regions can affect protein function, SNPs in non-coding regions can influence gene regulation and expression.

30. (a) Animal cell culture

Passage:
Animal cells can be grown in glass or plastic vessels with nutrient medium. These need to be given fresh medium periodically. The infant animal cells grow only to adulthood and not any further. While growing, they show the phenomenon of contact inhibition, but cancer cells don’t show this characteristic.

(i) What is contact inhibition?

Answer:
Contact inhibition is a process where normal animal cells stop growing or dividing when they come into contact with each other. This characteristic helps in controlling the cell population and maintaining tissue structure.

(ii) Which property of cells is studied by oncologists to determine whether cells are normal or cancerous?

Answer:
Oncologists study the phenomenon of contact inhibition and uncontrolled cell growth to determine whether cells are normal or cancerous. Cancerous cells do not exhibit contact inhibition and continue to divide even when in contact with other cells.

(iii) As in vivo environment is different from in vitro environment, how does it affect cells grown in culture? Mention any two.

Answer:

  1. Cells grown in vitro (in culture) often face altered nutrient and oxygen conditions compared to those in vivo (within the body), which can affect their growth and behavior.
  2. In vitro, cells do not experience the same physical interactions with other cells and tissues (e.g., extracellular matrix, immune responses), which can influence their morphology, function, and differentiation.

OR

(iii) Mortality is associated with all normal animal cells. Justify giving reason.

Answer:
Mortality is associated with normal animal cells because they undergo a limited number of divisions before they stop growing, a phenomenon known as cellular senescence. This process is regulated by telomere shortening and other mechanisms, ensuring that cells do not divide indefinitely and eventually die.

SECTION E

31. (a)
(i) Differentiate between primary and secondary metabolites.

Answer:

  • Primary Metabolites are directly involved in growth, development, and reproduction. They are essential for the basic metabolic processes in a cell, such as amino acids, proteins, carbohydrates, and lipids. These are produced during the normal growth of the organism.
  • Secondary Metabolites are not directly involved in normal growth, development, or reproduction, but they often help the organism survive in its environment. These include alkaloids, terpenoids, and flavonoids, which are used in defense mechanisms, attraction of pollinators, or as antibiotics. They are produced in the stationary phase of growth.

(ii) Name three industrially important plant secondary metabolites produced through cell and tissue culture, along with their use.

Answer:

  1. Alkaloids (e.g., morphine from Papaver somniferum)
    • Use: Pain relief and medicinal purposes.
  2. Flavonoids (e.g., quercetin from Onion or Citrus fruits)
    • Use: Antioxidant properties and potential health benefits.
  3. Terpenoids (e.g., taxol from Taxus species)
    • Use: Cancer treatment (anticancer properties).

OR

(b)
(i) According to WHO estimates, approximately 228 million children are affected due to Vitamin A deficiency. How has genetic engineering provided/developed a solution to the same? Explain.

Answer:
Genetic engineering has provided a solution through the development of Golden Rice, a genetically modified rice that is enriched with beta-carotene, which the body can convert into Vitamin A. This biofortified rice has been designed to help combat Vitamin A deficiency, particularly in developing countries where rice is a staple food, thus improving nutrition and reducing deficiency-related diseases.

(ii) Why is nutritional quality of cereals and legumes limited?

Answer:
The nutritional quality of cereals and legumes is limited because they often lack certain essential amino acids. For example, cereals may be deficient in lysine and tryptophan, while legumes may lack methionine and cysteine. These deficiencies can limit their ability to provide a complete protein source when consumed alone.

(iii) Name two essential amino acids which are deficient in pulses.

Answer:

  1. Methionine
  2. Cysteine

32. (a) (i)

Steps of Recombinant DNA Technology:

  1. Isolation of the gene of interest: The specific gene is isolated from an organism using restriction enzymes.
  2. Insertion of the gene into a vector: The gene is inserted into a plasmid or viral vector that can carry it into the host organism.
  3. Introduction into host cells: The recombinant DNA is introduced into a suitable host cell, often using transformation or transfection methods.
  4. Selection and expression: The host cells are selected based on the presence of the recombinant DNA, and the gene is expressed, producing the desired protein or product.

Two scientists involved in the generation of the first Recombinant DNA molecule:

  • Herbert Boyer
  • Stanley Cohen

Two products produced commercially using Recombinant DNA technology:

  • Insulin
  • Growth hormones

(ii) Why are Type II restriction enzymes preferred in Recombinant DNA Technology?

Answer:
Type II restriction enzymes are preferred because they cleave DNA at specific sequences and produce sticky or blunt ends, making it easier to ligate the target gene into a vector. These enzymes recognize specific palindromic sequences and are highly predictable, which allows precise cutting of DNA for recombinant DNA techniques.

OR

(b) (i) Describe the technique to detect microbes from environmental samples present in very small numbers.

Answer:
One common technique used to detect microbes in small numbers is Polymerase Chain Reaction (PCR). PCR amplifies specific DNA sequences, allowing detection of microorganisms even when they are present in trace amounts. This is achieved by using primers specific to the target microbe’s DNA, which can exponentially replicate a particular region of the DNA, making it detectable.

(ii) Why is this technique getting popular in diagnostics?

Answer:
PCR is gaining popularity in diagnostics because it is highly sensitive, specific, and can detect even a single microbial DNA or RNA copy in a sample. It allows for rapid and accurate detection of pathogens, even those present in very low concentrations, making it invaluable for detecting infections early.

33. (a) (i) How are conventional vaccines different from recombinant vaccines?

Answer:

  • Conventional vaccines are made using killed or inactivated pathogens, or live attenuated pathogens that stimulate the immune system. Examples include the polio vaccine and the flu vaccine.
  • Recombinant vaccines are produced by inserting a gene from a pathogen into a vector (such as yeast or bacteria), which then expresses the pathogen’s protein to stimulate an immune response. Examples include the Hepatitis B vaccine and the HPV vaccine.

(ii) What are epitopes?

Answer:
Epitopes are the specific regions of an antigen molecule that are recognized by the immune system, specifically by antibodies or T-cell receptors. These are the parts of the antigen that trigger an immune response.

(iii) What are the advantages of preparing vaccines using epitopes?

Answer:

  • Reduced risk of infection: Since only the epitope (non-infectious part of the pathogen) is used, there is no risk of causing the disease.
  • Targeted immune response: The vaccine can specifically stimulate the immune system to recognize and fight the pathogen without including unnecessary components of the pathogen.

OR

(b) (i) Branched Chain Amino Acids (BCAA) are essential for the biosynthesis of muscle protein. How? Explain.

Answer:
Branched-chain amino acids (BCAAs) include leucine, isoleucine, and valine. These amino acids are essential because they are directly involved in protein synthesis in muscles. Leucine, in particular, activates the mTOR pathway, which promotes muscle growth. BCAAs help in the recovery and repair of muscle tissues after exercise by being incorporated into muscle proteins and preventing muscle breakdown.

(ii) What is the Biological Value of proteins?

Answer:
The Biological Value (BV) of a protein is a measure of how efficiently the body can use the protein for growth and maintenance. It is determined by the ratio of nitrogen retained in the body to the nitrogen absorbed from the protein. Higher BV indicates that the protein contains a better balance of essential amino acids.

(iii) What is Protein Efficiency Ratio?

Answer:
The Protein Efficiency Ratio (PER) is a measure of the effectiveness of a protein in promoting weight gain in animals. It is calculated by dividing the weight gained by an animal by the amount of protein consumed during the feeding period.

Protein Efficiency Ratio (in decreasing order):

  1. Whey
  2. Milk
  3. Casein
  4. Soya
  5. Wheat