CBSE Class 12 Sample Paper 2025 for Biotechnology

CENTRAL BOARD OF SECONDARY EDUCATION

SAMPLE PAPER
CLASS 12
2025

SAMPLE QUESTION PAPER
BIOTECHNOLOGY (045)
Class XII (2024-25)

Max. Marks: 70 Time allowed: 3 hours

General Instructions:
(i) All questions are compulsory.
(ii) The question paper has five sections and 33 questions.
(iii) Section–A contains 12 Multiple choice questions and 4 Assertion-Reasoning based
questions of 1 mark each; Section–B has 5 short answer questions of 2 marks each;
Section –C has 7 short answer questions of 3 marks each; Section-D has two case-based
question of 4 marks; Section-E has three long answer questions of 5 marks each.
(iv) There is no overall choice. However, internal choices have been provided in some
questions. A student has to attempt only one of the alternatives in such questions.
(v) Wherever necessary, neat and properly labeled diagrams should be drawn.
Section - A
Q. No. 1 to 12 are multiple choice questions. Only one of the choices is correct. Select
and write the correct choice as well as the answer to these questions.
1 An approach that utilises analysis of genome present in different 1
environment to screen presence of variety of molecules.
A. Metagenomics
B. Proteomics
C. Strain preservation
D. Mutant selection
2 In animal cell culture, the CO2 levels in the incubator is usually maintained 1
at-
A. 1-2%
B. 3-4%
C. 5-10%
D. 11-15%

3 Even if we know where the genes are in each genome, it’s difficult to count 1
them due to:
(i) splice variants
(ii) overlapping genes
(iii) Post – trancriptional events
(iv) Mutations

A. (i), (iii)
B. (i), (ii)
C. (iii), (iv)
D. (ii), (iv)

4 Avocado growers in Kerela want to find a way to genetically engineer their 1
crop to prevent it from ripening during shipping. This can be achieved by
introducing-
A. genes for carotenoid biosynthesis.
B. gene from Bacillus amyloliquefaciens.
C. ethylene forming gene(s).
D. gene for protein containing sulphur rich amino acids.

5 Microbial species used for commercial production of citric acid is- 1
A. Saccharomyces cerevisiae
B. Aspergillus niger
C. Streptomyces griseus
D. Aspergillus oryzae

6 To reduce the possibility of religation of vector without picking insert, the 1
following method or methods may be used-
(i) Use of DNA Ligase
(ii) Use of Alkaline Phosphatase
(iii) Use of two different Restriction enzymes for cloning
(iv) Hybridoma technology
Select the correct answer from options below
A. (i), (iv)
B. (ii), (iii)
C. (iii), (iv)
D. (ii), (iv)

7 In a comparative cDNA microarray, the cDNA obtained from the normal and 1
diseased cells are labelled with red and green fluorescent dyes
respectively. The yellow colour of the spot indicates-
A. Gene is expressed only in normal cells.
B. Gene is not expressed either in normal cells or in diseased cells.
C. Gene expressed only in diseased cells.
D. Gene expressed in equal measure in both types of cells.

8 Which disease has its locus on chromosome no 1 and 6? 1
A. Huntington's disease
B. Migraine
C. Alzheimer’s disease
D. Cystic fibrosis

9 A molecular disease which leads to increased hydrophobic interactions 1
within the haemoglobin protein is-
A. Thalassemia
B. Sickle Cell anaemia
C. Mad Cow
D. SCID
10 Interleukin-2 produced using CHO cell line is used for- 1
A. anaemia therapy.
B. cancer therapy.
C. stroke.
D. treatment of autoimmune disease.

11 Proteome of a given cell is dynamic because: 1
A. In response to internal and external changes the biochemical
machinery of the cell could be changed.
B. In response to internal and external changes the biochemical
machinery of the cell could not be changed.
C. No direct relationship exists between internal and external changes
in the biochemical machinery of the cell.
D. Indirect relationship exists between internal and external in changes
the biochemical machinery of the cell.
12 A novel gene that codes for the epitope has been introduced into yeast cells 1
to produce-
A. Hepatitis B Vaccine
B. Subtilisin
C. EPO
D. tPA

Question No. 13 to 16 consist 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 the true and Reason (R) is a correct
explanation of Assertion (A).
B. Both Assertion (A) and Reason (R) are the true but Reason (R) is not a correct
explanation of Assertion (A).
C. Assertion (A) is true and Reason (R) is false.
D. Assertion (A) is false and Reason (R) is true.
13 Assertion (A) - Patients who are administered monoclonal antibodies 1
against CD3, can accept renal allograft.
Reason (R) - Monoclonal antibodies block T cell function

14 Assertion (A) - Foaming is a problem in most microbiological cultures. 1
Reason (R) - It is caused due to the presence of fatty acids and silicones
in the culture medium.

15 Assertion (A) - Yeast cells having YEp plasmid can grow on a medium 1
lacking leucine and hence can be selected
Reason (R) - LEU2 gene codes for an enzyme required for the synthesis
of amino acid leucine.

16 Assertion (A) - Long-term callus and cell suspension cultures and plants 1
developed from such cultures may have chromosomal variations called
somaclonal variations.
Reason(R) - Somaclonal variations may lead to improvement in crops like
disease resistance in potatoes.

Section - B
17 The following table lists the common cloning vectors with the size of insert 2
that can be cloned into them.
Mark A, B, C and D in the table.

Vector Type Insert size (kb)
Plasmid 0.5-8
A 9-23
Cosmid B
C 50-500
YAC D

18 Based on microscopic observation, how can pathologist differentiate 2
between cancerous and non-cancerous cells?

19 Attempt either option A or B. 2
A. What is inverted microscope and why is it used instead of compound
microscope for observing animal cells in culture?
OR
B. Why are B lymphocytes fused with myeloma cells in hybridoma
technique? Give an important application of this technique.

20 Why is 2D Gel Electrophoresis considered a suitable technique for studying 2
Proteomics?

21 Which database was created to manage the redundancy in EST data? 2
What is the role of the curator in Bioinformatics?

Section - C

22 A. Why has sickle cell trait been selected in population where malaria is 3
endemic?
B. What is the molecular basis of sickle cell anaemia?
C. How can we differentiate between a normal RBC and Sickle cell RBC?

23 Why is the nutrient medium autoclaved before using it for culturing 3
microbes? How would you sterilize a heat-labile substance such as
antibiotic solution?

24 A. Identify (a), (b), (c) and (d) in the following table showing some 3
industrially important plant secondary metabolites, their plant source
and uses-
Product Plant source Uses
Vincristine (a) Anticarcinogenic
(b) Papaver spp Analgesic
Cinchona
Quinine (c)
officinalis
Taxol Taxus spp. (d)

B. The indiscriminate use of such valuable medicinal and other plants has
brought them to near extinction. Suggest a possible solution to this .

25 How does the charge relay system operate in chymotrypsin? 3

26 The gene for a eukaryotic polypeptide hormone was isolated, cloned and 3
over-expressed in a bacterium. After the polypeptide was purified from the
bacterium, it failed to function in the organism from which the gene was
isolated. Suggest all the possibilities why the recombinant protein was
inactive.

27 Illustrate essential steps involved in raising a chimeric mouse using stem 3
cell technology.

28 Attempt either option A or B. 3
A. Selection is an important step in genetic engineering. You are given
ampicillin and tetracycline antibiotics. Using these antibiotics, which
selection technique could be used to differentiate between
recombinant and non-recombinant cells?
OR
B. Which microbial cells have been used extensively for functional
expression of eukaryotic genes and why?

Section - D
29 The below figure depicts a process used in diagnosis of a disease. 4

A. Identify the mutation and the disease shown in the diagram. (1)
B. Which technique can help in the identification of this technique? (1)
Attempt either subpart C or D.
C. Write down the steps occurring during nick translation. (2)
OR
D. How do extent of severity of the disease be detected in the above
process?

30 Isolation of microbial product 4
Once the fermentation is complete, it is necessary to recover the desired
metabolite. Minimally, this will involve separation of the cells from the
fermentation broth. But it may also include, purification of the metabolite
with or without cell disruption; cell disruption will be necessary if the
metabolite is intracellular. Such operations are referred to as downstream
processing. The steps involved in isolation of the desired microbial product
are: (1) separation of cells from the fermented broth, (2) cell disruption if
the product is intracellular or concentration of the broth if the product is
extracellular (3) initial purification of the metabolite, (4) metabolite-specific
purification in which the metabolite of interest is purified to a high degree,
and (5) polishing of the metabolite (bringing it to 98 -100% purity) where it
is further concentrated and formulated for use.

A. Cite an example of pure metabolite that can be obtained from above
depicted flow chart.
B. Suggest a suitable term which includes all the steps mentioned above.

Attempt either subpart C or D.
C. In the second step mentioned above, “Which part will you use to isolate
intracelluar product?”
OR
D. Why is it generally recommended to have minimum number of steps in
these isolation processes?
Section - E
31 Attempt either option A or B. 5
A. A protein with molecular weight of 10,000 contains 4, 3, 2, and 1
charge. Calculate the m/z ratio of protein ions at which Mass
spectrometer detects them. Draw the Mass spectrum corresponding to
the above mentioned ions.

OR
B. A doctor has to prescribe a protein rich diet to sportsmen to improve
their performance. What are the three parameters that the doctor
should consider while prescribing these protein sources?
32 Attempt either option A or B. 5
A. Write the basic steps with principles (starting from an explant) involved
in obtaining a regenerated plant. Suggest any two applications of plant
tissue culture.
OR
B. Indicate how intergeneric somatic hybrids can be made. Give an
example. What are cybrids? How are edible vaccines advantageous
over recombinant vaccines produced by bacterial fermentation?

33 Attempt either option A or B. 5
A. Who invented the dideoxynucleotide chain termination method?
Schematically explain the method.
OR
B. Why is the dye termination method considered better than chains
termination technique? (Any two) Why is the autoradiogram read from
bottom to top (anode to cathode)? Why do bacteria produce restriction
enzymes and how do they protect their own DNA from its action?

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