Class 12

Class 12 Biotechnology 2023 Solved Paper

Class 12 Biotechnology PYQ 2023 Solved

Time allowed: 3 hours

Maximum Marks: 70

General Instructions :

Read the following instructions carefully and follow them :

(i) This question paper contains 33 questions. All questions are compulsory.

(ii) Question paper is divided into five sections Section A, B, C, D, and E.

(iii) Section A: Questions #1 to 16 are Multiple Choice Type Questions. Each question carries 1 mark.

(iv) Section B: Questions #17 to 21 are Very Short Answer Type Questions. Each question carries 2 marks.

(v) Section C: Questions #22 to 28 are Short Answer (SA) Type Questions. Each question carries 3 marks.

(vi) Section D: Questions #29 and 30 are Case-based Questions carrying 4 marks each. Each question has sub-parts with internal choice in one sub-part.

(vii) In Section E: Questions #31 to 33 are Long Answer (LA) Type Questions. Each question carries 5 marks.

(viii) There is no overall choice given in the question paper. However, an internal choice has been provided in few questions in all the Sections except Section A.

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

2. Microbial source of Hind III restriction enzyme is:

(a) Haemophilus aegyptius
(b) Haemophilus influenzae
(c) Haemophilus haemolyticus
(d) Haemophilus felis

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.

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

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

6. SCID disease is caused by absence of enzyme:

(a) Adenosine synthase
(b) Adenosine deaminase
(c) Adenosine phosphatase
(d) Adenosine aminase

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

8. Alcaligenes eutrophus is associated with the production of:

(a) Streptomycin
(b) Penicillin
(c) Hepatitis antigen
(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)

10. Artemisin obtained from Artemisia species is used as

(a) Antimalarial
(b) Antifertility
(c) Anticarcinogenic
(d) Analgesic

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

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

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.

Ans: (b) Both Assertion (A) and Reason (R) are true, but Reason is not the correct explanation of Assertion

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.

Ans: (a) Both Assertion (A) and Reason (R) are true and Reason is the correct explanation of Assertion

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.

Ans: (c) Assertion (A) is true, but Reason (R) is false.

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.

Ans: (d) Assertion ( A) is false, but Reason ( R) is true.

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. (Show sucrose breakdown) No result was obtained. Why?

(b) What can be done to select these recombinants ? 2

Ans:

(a) Galactosidase enzyme is produced by the LacZ gene, which uses X-gal as substrate/ sucrose is not a substrate for the lacZ gene product (-galactosidase).

(b) Add X-gal in the nutrient medium to select the recombinants by blue white selection method.

18. How does mosquito repellent work? Mention its major chemical constituents. 2

They work by affecting nerve transmission in insects/ organophosphate compounds can selectively react with an acidic serine residue, thereby knocking off enzyme activity (by inactivating the brain enzyme acetylcholine esterase). Derivatives of organophosphates – Malathion and Parathion, which are not toxic to humans.

19. There are about 1-6 million to 3 2 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. 2

SNPs may or may not affect gene function depending upon the exact base change and where it occurs in the human genome:

SNP in the coding region affects gene function, which is protein or enzyme formation.
SNP in the non-coding region does not affect gene function but helps in DNA Fingerprinting/ Forensic Science.

20. (a) Differentiate between Primary cell cultures and Secondary cell cultures. 2

(a) Any 2 differences:-

Primary Cell Cultures	Secondary Cell Cultures
(a) These are prepared by dissociating cells from parental tissue (such as kidney, liver, or tissue of live animals) by mechanical or enzymatic methods and are maintained in suitable culture medium.	(a) These are prepared by cells obtained from primary cell culture, which are subcultured (split) in fresh nutrient medium.
(b) Time-consuming	(b) Not time-consuming
(c) Can show considerable variations from one preparation to another, particularly if prepared by different individuals	(c) Does not show considerable variation
(d) Characteristics of cells in culture depend on original source	(d) Cells can get spontaneously transformed/ altered, giving rise to continuous cell lines

(b) Differentiate between Finite cell lines and Continuous cell lines. 2

Any 2 differences:-

Finite Cell Lines	Continuous Cell Lines
(a) Limited life span	(a) Can grow for a longer time/unlimited lifespan
(b) Show contact inhibition	(b) Do not show contact inhibition
(c) Doubling time is 24 – 96 hours	(c) Doubling time is 12 to 24 hours
(d) Show density limitation	(d) Density limitation is reduced or lost.
(e) The mode of growth of cells is in monolayer form.	(e) The mode of growth of cells is either monolayer or suspension form
(f) Growth rate is slow	(f) Growth rate is rapid
(g) Show anchorage dependence	(g) Do not show anchorage dependence
(h) Cells are not transformed	(h) Cells are transformed
(i) Cells do not show a change in ploidy( change in the basic number of chromosomes)	(i) Cells can show the change in ploidy( change in the basic number ofchromosomes)
(j) Any suitable example	(j) Any suitable example

21. How will you perform laboratory screening for microorganism producing an antibiotic? 2

Laboratory screening for microorganisms producing an antibiotic can be done by:

(Any 1 method)

Growing the culture on an agar plate in the presence of the bacterium against which antimicrobial activity is desired.
Immunological methods for the detection of microbial products using specific antibodies
Using a variety of probes for the detection of organisms producing specific products..
Brief explanation: Blue white selection / Replica Plating / Insertional Inactivation
Any other relevant method

SECTION C

22. Give reason for the following : 3

(a) Baffle flasks have V-shaped notch.

(b) Excess foaming in microbiological processes is a problem.

(c) Slaughter-house wastes are used to prepare media for microbiological processes.

(a) Improves the efficiency of O2 transfer due to increased turbulence of the agitated culture medium.
(b) Excess foaming denatures proteins and provides a hindrance to the free diffusion of O₂ in the medium.
(c) Slaughterhouse wastes are a good source of Nitrogen/proteins / amino acids.

23. (a) How are mouse models created? Write two major applications in the field of stem cell technology. 3

(a) Mouse models are created by selectively removing a gene and making other precise genetic modifications in the mouse ES cells / Creation of chimeric mice. Major applications in the field of stem cell technology are:-

Understanding the genetic basis of a disease.
Search for new diagnostics and therapeutic modalities.
It can be used for differentiating into all types of tissues.
It can act as a repair system for the body.
Creation of a Chimeric mouse.
Creation of gene knockouts/mouse models.
It can be grown and transformed into specialized cells.
Used in medical therapies.
Used in medical conditions such as: Leukemia, Heart diseases, Paralysis, Alzheimer’s, Parkinson’s, Huntington’s, burns.
(Any other relevant point) (Any two)

(b) Complete the flowchart for creating gene knockout by filling A, B, and C. 3

Selection of a gene of interest for knockout

↓

Place in plasmid

↓

Inject plasmid into A

↓

Homologous recombination

↓

Selection with B

↓

Injecting it into C

(b)

A – Embryonic stem cells / ICM
B – Resistance marker
C – Blastocyst

(For visually-impaired candidates only in lieu of Q. 23 (b))

(b) What is BLAST? What are the principles involved in this search program? 3

(b)BLAST is the Basic Local Alignment Search Tool. The principles involved in this search program are :

(i) Comparison of a given sequence with sequences in the database to either reward a match or penalize a mismatch.
(ii) Top-scoring matches are ranked according to set criteria that help to distinguish between similarity due to ancestral relationship or random chance.
(iii) True matches are further examined thoroughly with other details accessible through Entrez and other tools at NCBI.
(iv) Sequences can be compared for homology and paralogy. (Any two points)

24. Pichia pastoris is the most suitable host to express eukaryotic genes. Support the statement giving three reasons. 3

Pichia pastoris is the most suitable host to express eukaryotic genes because of the following reasons:-

It has strong inducible promoters.
It is capable of making post-translational modifications similar to those performed by human cells.
Downstream processing is simpler as Pichia pastoris does not secrete its own proteins into the fermentation medium.

25. Transgenic crops are facing challenges globally. What are the major concerns about these GM crops? 3

The major concerns about GM Crops are: ( Any three)

May cause allergy and toxicity.
Effect of GM crops on biodiversity and the environment.
Effect on non-target and beneficial insects/ microbes.
Transgenes may escape through pollen to related plant species and may lead to the development of superweeds.
GM crops may change the fundamental vegetative nature of plants as genes from animals are being introduced into crop plants.
Antibiotic resistance marker genes used to produce transgenic crops may horizontally transfer into microbes and thus exacerbate the problem of antibiotic resistance in humans and animal pathogens.
May lead to a change in the evolutionary pattern.
Any other relevant point

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

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

(c) m-RNA and protein expression levels in a cell do not always correlate. Why? 1+1+1

(a) Proteins have maximum diversity in function because : They are made up of 20 different amino acids (with a variety of side chains) / unique 3D structures of proteins, and thereby functions / post-translational modifications in proteins/protein sizes, and amino acid sequence combinations of proteins.
(b) The proteome of a cell is dynamic because the biochemical machinery of a cell can be modulated in response to internal and external environmental changes.
(c) mRNA and protein expression levels in a cell do not always correlate because of various post-transcriptional and post-translational regulations and modifications, mRNA editing, and alternative splicing. (any other relevant point)

27. How is MALDI (Matrix Assisted Laser Desorption Ionisation) used to volatalise and protonate peptides and proteins? 3

To use MALDI (Matrix Assisted Laser Desorption Ionisation) to volatilize and protonate peptides and proteins :

The sample is transferred from a condensed phase to a gas phase with the help of a solid matrix.
Ion formation is achieved by directing a pulsed laser beam at a sample suspended/dissolved in a matrix.
The matrix absorbs laser light energy, which causes the matrix material to vaporize. In the gas phase, the matrix plays a role in sample ionization.

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

(b) What are shuttle vectors?

(a) The essential features that a vector should possess are:-

It must contain an origin of replication (ori)
It should contain a selectable marker gene
It should contain a multiple cloning site (MCS) or a polylinker / one unique restriction enzyme recognition site.
It should be small in size. ( Any Two points)

( b) Shuttle vectors ( for eg, YEp) can exist in both prokaryotic cells (eg, E. coli ) and in eukaryotic cells (eg. yeast) .

These vectors consist of two types of origin of replication (ori) and selectable marker genes.

SECTION D

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

Single nucleotide polymorphisms (SNPs) are common genetic variations among people. Each SNP represents a difference in a 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? 1

(ii) SNPs can decide our susceptibility to, or protection from all kinds of diseases. Give any one example to support the same. 2

(iii) Why is SNP analysis used in population genetics? 1

(iii) Do SNPs occur only in coding regions of human genome or in both coding and non-coding regions? 1

Ans: (a)

(i) SNPs help to predict how patients are likely to respond to a particular drug/susceptibility to or protection from all kinds of diseases/severity of illness/body response to treatment.

(ii) A single base difference in the APOE gene is associated with Alzheimer’s disease / A simple deletion within the chemokine receptor gene CCR5 leads to resistance to HIV infections and development of AIDS / Migraine /or any other relevant example. ( Any one example )

(iii) SNP analysis is used in population genetics as some SNPs vary in different frequencies between populations.

(iii) SNPs occur in both coding and non-coding regions of the human genome.

30. (a) Animal cell culture

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 phenomenon of contact inhibition, but cancer cells don’t show this characteristic.

(i) What is contact inhibition? 1

(ii) Which property of cells is studied by oncologists to determine whether cells are normal or cancerous? 1

(iii) As in-vivo environment is different from in-vitro environment, how does it affect cells grown in culture? Mention any two. 2

(iii) Mortality is associated with all normal animal cells. Justify giving reason. 2

Ans: (a)

(i) Contact Inhibition: Animal cells stop growing further as they reach the walls of a container (confluency).
(ii) Properties of animal cells studied by oncologists to differentiate between normal and cancerous cells are:
- • Differences in growth patterns by using colony colony-forming assay.
- • Cancerous cells lose contact inhibition, pile on each other due to uncontrolled growth, appear more rounded in shape, whereas Normal cells show contact inhibition, grow in monolayer mode, and do not appear more rounded in shape. (Any one )

(iii) Difference in the in vivo and in vitro environment affects the adherence of cells to the culture vessel / their shape/ rate of proliferation. (Any 2 points)

(iii) Depending on the tissue from which they have been isolated, all normal animal cells can be grown for limited generations even in the best nutritive media,

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

(ii) Name three industrially important plant secondary metabolites produced through cell and tissue culture, along with their use. 2+3

(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.

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

(iii) Name two essential amino acids which are deficient in pulses. 3+1+1

Ans: (a)

(i) Primary metabolites are chemicals produced by plants required for basic metabolic processes, for example, sugars, lipids, amino acids, etc. Some additional products produced in small amounts, like alkaloids (used in medicine), resins, tannins, latex, etc, which have a role in the defense mechanism/protection of the plant against pests and pathogens/feeding by animals are called secondary metabolites.

(ii) Any 3 from the following table:

Plant secondary metabolites produced through cell and tissue culture.	Use
Artemisin	Antimalarial
Azadirachtin	Insecticidal
Berberine	Antibacterial, Antiinflammatory
Capsaicin	Rheumatic pain treatment
Codeine	Analgesic
Digoxin	Cardiac tonic
Diosgenin	Antifertility
Scopolamine	antihypertensive
Quinine	Antimalarial
Shikonin	Antimicrobial
Taxol	Anticarcinogenic
Vincristine	Anticarcinigenic

(b)

(i) By developing genetically engineered rice (Golden rice) which is enriched in pro-vitamin A (beta-carotenoids), by introducing three genes involved in the biosynthetic pathway for carotenoid under the control of endosperm endosperm-specific promoter, so that gene products (enzymes) are synthesised in the rice endosperm.

(ii) Because of a deficiency of the essential amino acids.

(iii) Two essential amino acids that are deficient in pulses are methionine and tryptophan.

32. (a) (i) Draw diagram showing schematic representation of the basic steps in Recombinant DNA Technology. 4

(ii) Why are Type II restriction enzymes preferred in the above-mentioned technology? 1

Ans: (a) (i)

(ii) Type II restriction enzymes recognise and cut DNA within a specific sequence, typically consisting of 4 to 8 base pairs (palindromic sequence, restriction site ).

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

(ii) Why is this technique getting popular in diagnostics? 3+2

(b) (i) Polymerase Chain Reaction (PCR) Technique:-

Denaturation:- DNA is heated to a high temperature above 800 °C, which results in DNA strand separation.
Annealing:- Each single strand anneals with the primer at a lower temperature between 50-60°C.
Extension:- Extension occurs at around 700 °C in 5’ to 3’ direction using enzyme Taq polymerase to extend each primer using dNTPs and the DNA strand as template.

(ii) PCR-based diagnostics is faster, safer, and more specific because it does not use live pathogens instead, DNA from infected tissue is isolated for the PCR technique. Small quantities of DNA can be amplified by PCR.

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

(ii) What are epitopes?

(iii) What are the advantages of preparing vaccines using epitopes? 2+1+2

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

(ii) What is Biological value of proteins?

(iii) What is Protein Efficiency Ratio? Arrange the following proteins in decreasing order of protein efficiency ratio: 3+1+1

Milk, Casein, Soya, Wheat, Whey

a) (i) Conventional vaccines utilise heat-inactivated bacteria or virus or their surface proteins to generate immunity against various specific diseases. It has undesirable effects like fever ( caused due to incomplete inactivation of some of the components ).
The recombinant vaccine is based on selected epitopes. It is safe to use.
(ii) The specific sequences of amino acids in the protein that stimulate an immune response are known as epitopes.
(iii) Advantages of preparing vaccines by using epitopes are that these vaccines may provide optimal design, scope for micromanipulation, unhindered supply and safety needed for an effective vaccine. (Any 2)

(b)

(i)BCAA helps in increasing the bioavailability of high complex carbohydrates intake, and they are absorbed by muscle cells for anabolic muscle building activity. During exercise, BCAAs are released from the skeletal muscles, their carbon part is used as fuel, and the nitrogen part is used to make alanine, which goes to the liver where it is turned into glucose for energy. BCAAs reduce muscle breakdown and act as an energy source before and after exercise. It delays exhaustion and is important for muscle growth.
(ii)Biological Value measures the amount of protein nitrogen that is retained by the body from a given amount of protein nitrogen that has been consumed.
(iii) Protein Efficiency Ratio (PER) is a measure of growth expressed in terms of weight gain of an adult by consuming 1 g of food protein. Proteins in decreasing order of protein efficiency ratio are: Whey>Milk> Casein >Soya >Wheat