CBSE Class 12 Question Paper 2023 Solution Biotechnology

e s t i o n P a p er
Qu
Solu t i o n
2023

Marking Scheme

Strictly Confidential

(For Internal and Restricted use only)

Senior School Certificate Examination, 2023

SUBJECT NAME BIOTEHCNOLOGY .(SUBJECT CODE 045) (PAPER CODE 99)

General Instructions: -

1 You are aware that evaluation is the most important process in the actual and correct
assessment of the candidates. A small mistake in evaluation may lead to serious problems
which may affect the future of the candidates, education system and teaching profession.
To avoid mistakes, it is requested that before starting evaluation, you must read and
understand the spot evaluation guidelines carefully.

2 “Evaluation policy is a confidential policy as it is related to the confidentiality of the
examinations conducted, Evaluation done and several other aspects. Its’ leakage to
public in any manner could lead to derailment of the examination system and affect
the life and future of millions of candidates. Sharing this policy/document to
anyone, publishing in any magazine and printing in News Paper/Website etc may
invite action under various rules of the Board and IPC.”

3 Evaluation is to be done as per instructions provided in the Marking Scheme. It should not
be done according to one’s own interpretation or any other consideration. Marking
Scheme should be strictly adhered to and religiously followed. However, while
evaluating, answers which are based on latest information or knowledge and/or are
innovative, they may be assessed for their correctness otherwise and due marks be
awarded to them. In class-X, while evaluating two competency-based questions,
please try to understand given answer and even if reply is not from marking scheme
but correct competency is enumerated by the candidate, due marks should be
awarded.

4 The Marking scheme carries only suggested value points for the answers

These are in the nature of Guidelines only and do not constitute the complete answer. The
students can have their own expression and if the expression is correct, the due marks
should be awarded accordingly.

5 The Head-Examiner must go through the first five answer books evaluated by each
evaluator on the first day, to ensure that evaluation has been carried out as per the
instructions given in the Marking Scheme. If there is any variation, the same should be

zero after delibration and discussion. The remaining answer books meant for evaluation
shall be given only after ensuring that there is no significant variation in the marking of
individual evaluators.

6 Evaluators will mark( √ ) wherever answer is correct. For wrong answer CROSS ‘X” be
marked. Evaluators will not put right (✓)while evaluating which gives an impression that
answer is correct and no marks are awarded. This is most common mistake which
evaluators are committing.

7 If a question has parts, please award marks on the right-hand side for each part. Marks
awarded for different parts of the question should then be totaled up and written in the left-
hand margin and encircled. This may be followed strictly.

8 If a question does not have any parts, marks must be awarded in the left-hand margin and
encircled. This may also be followed strictly.

9 If a student has attempted an extra question, answer of the question deserving more
marks should be retained and the other answer scored out with a note “Extra Question”.

10 No marks to be deducted for the cumulative effect of an error. It should be penalized only
once.

11 A full scale of marks __________(example 0 to 80/70/60/50/40/30 marks as given in
Question Paper) has to be used. Please do not hesitate to award full marks if the answer
deserves it.

12 Every examiner has to necessarily do evaluation work for full working hours i.e., 8 hours
every day and evaluate 20 answer books per day in main subjects and 25 answer books
per day in other subjects (Details are given in Spot Guidelines).This is in view of the
reduced syllabus and number of questions in question paper.

13 Ensure that you do not make the following common types of errors committed by the
Examiner in the past:-

● Leaving answer or part thereof unassessed in an answer book.
● Giving more marks for an answer than assigned to it.
● Wrong totaling of marks awarded on an answer.
● Wrong transfer of marks from the inside pages of the answer book to the title page.
● Wrong question wise totaling on the title page.
● Wrong totaling of marks of the two columns on the title page.
● Wrong grand total.
● Marks in words and figures not tallying/not same.
● Wrong transfer of marks from the answer book to online award list.
● Answers marked as correct, but marks not awarded. (Ensure that the right tick mark is
correctly and clearly indicated. It should merely be a line. Same is with the X for
incorrect answer.)
● Half or a part of answer marked correct and the rest as wrong, but no marks awarded.

14 While evaluating the answer books if the answer is found to be totally incorrect, it should
be marked as cross (X) and awarded zero (0)Marks.

15 Any un assessed portion, non-carrying over of marks to the title page, or totaling error
detected by the candidate shall damage the prestige of all the personnel engaged in the
evaluation work as also of the Board. Hence, in order to uphold the prestige of all
concerned, it is again reiterated that the instructions be followed meticulously and
judiciously.

16 The Examiners should acquaint themselves with the guidelines given in the “Guidelines
for spot Evaluation” before starting the actual evaluation.

17 Every Examiner shall also ensure that all the answers are evaluated, marks carried over to
the title page, correctly totaled and written in figures and words.

18 The candidates are entitled to obtain photocopy of the Answer Book on request on
payment of the prescribed processing fee. All Examiners/Additional Head Examiners/Head
Examiners are once again reminded that they must ensure that evaluation is carried out
strictly as per value points for each answer as given in the Marking Scheme.

MARKING SCHEME

SUBJECT : BIOTECHNOLOGY THEORY (045)

AISSCE 2023

SET 4 QP. CODE 99

SESSION: 2022-23

GENERAL INSTRUCTIONS :

a. The Marking Scheme carries suggested value points for the answers.
b. These are guidelines which constitute the complete answer.
c. The students can have their own expression and if the expression is correct the marks can
be awarded accordingly.

MARKING SCHEME
BIOTECHNOLOGY (045)
SET-4 ( Series ∑HEFG)
Q.P. CODE 99
(2022-23)

SECTION – A

1 (b) LacZ gene 1
1
2 (b) Haemophilus influenzae
3 (b) Four ddNTPs are ddATP, ddUTP, ddCTP and ddGTP are needed 1
4 (a) His-Asp-Ser 1
5 (a) Yeast 1
6 (b) Adenosine deaminase 1

7 (a) Rigby and Paul Berg 1

8 (d) Poly-3-hydroxybutyrate 1
9 (d) Both (a) and (c) 1
10 (a) Antimalarial 1
11 (b) Are abiotic stress tolerant 1

12 (a) Haemophilia A 1

13 (b) Both Assertion (A) and Reason (R) are true, but Reason is not the correct explanation of 1
Assertion

14 (a) Both Assertion (A) and Reason (R) are true and Reason is the correct explanation of Assertion 1

15 (c) Assertion (A) is true, but Reason (R) is false. 1

16 (d) Assertion ( A) is false, but Reason ( R) is true. 1

SECTION – B

17 (a) -galactosidase enzyme is produced by LacZ gene which uses X-gal as substrate/ sucrose is 1+1=2
not a substrate for lacZ gene product (-galactosidase).
(b) Add X-gal in nutrient medium to select the recombinants by blue white selection method.

18
They work by affecting nerve transmission in insects/ organophosphate compounds can
1+1 = 2
selectively react with an acidic serine residue thereby knocking off enzyme activity (by
inactivating brain enzyme acetylcholine esterase).

Derivatives of organophosphates - Malathion and Parathion which are not-toxic to humans.

19
SNPs may or may not affect gene function depending upon the exact base
change and where it occurs in the human genome:
• SNP in coding region affects gene function that is protein or enzyme 1+1= 2
formation.
• SNP in non-coding region does not affect gene function but helps in
DNA Fingerprinting/ Forensic Science.

20
(a) Any 2 differences :-
1+1 = 2
Primary Cell Cultures Secondary Cell Cultures
(a) These are prepared by dissociating (a) These are prepared by cells
cells from parental tissue (such as obtained from primary cell culture
kidney, liver or tissue of live animals) which are subcultured (split) in
by mechanical or enzymatic methods fresh nutrient medium.
and maintained in suitable culture
medium.
(b) Time consuming (b) Not time consuming

(c) Can show considerable variations (c) Does not show considerable
from one preparation to another, variation
particularly if prepared by different
individuals

(d) Characteristics of cells in culture (d) Cells can get spontaneously
depend on original source transformed/ altered giving rise to
continuous cell lines

OR

(b) Any 2 differences :-

Finite Cell Lines Continous Cell Lines

(a) Limited life span (a) Can grow for longer time/unlimited
lifespan
1+1 = 2
(b) Show contact inhibition (b) Do not show contact inhibition

(c) Doubling time is (c) Doubling time is 12 to 24 hours
24 – 96 hours

(d) Show density limitation (d) Density limitation is reduced or lost.

(e) (e) Mode of growth of cells is either
Mode of growth of cells is in monolayer or suspension form
monolayer 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 change in ploidy (i) Cells can show change in ploidy
( change in basic number of ( change in basic number of
chromosomes) chromosomes)
(j) Any one suitable example (j) Any one suitable example

21 Laboratory screening for microorganism producing an antibiotic can be done by:
(Any 1 method) 2

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

SECTION C

22 (a) Improves the efficiency of O2 transfer due to increased turbulence of the agitated 1
culture medium.
(b) Excess foaming denatures proteins and provides hindrance to free diffusion of O 2
1
in medium.
(c) Slaughterhouse wastes are a good source of Nitrogen / proteins / amino acids. 1

23 (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:- 1
1. Understanding the genetic basis of a disease.
2. Search for new diagnostics and therapeutic modalities.
3. Can be used for differentiating into all types of tissues.
4. Can act as a repair system for the body.
5. Creation of Chimeric mouse.
6. Creation of gene knockouts/mouse models.
7. Can be grown and transformed into specialized cells. 1+1
8. Used in medical therapies.
9. Used in medical conditions such as: Leukemia, Heart diseases, Paralysis, Alzheimer's,
Parkinson's, Huntingtons, burns.
10. (Any other relevant point)
(Any two)
OR

(b)
A - Embryonic stem cells / ICM 1+1+1=3
B - Resistance marker
C - Blastocyst

For visually impaired candidates only in lieu of Q23 (b)
(b)
• BLAST is Basic Local Alignment Search Tool
1
• Principles involved in this search program are :
(i) Comparison of a given sequence with sequences in 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
1+1
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)

Pichia pastoris is the most suitable host to express eukaryotic gene because of the
24 following reasons :-
1. It has strong inducible promoters.
2. It is capable of making post-translational modifications similar to those performed
by human cells. 1+1+1=3
3. Downstream processing is simpler as Pichia pastoris does not secrete its own
proteins into the fermentation medium.

25 The major concerns about GM Crops are: ( Any three)
• May cause allergy and toxicity.
• Effect of GM crops on biodiversity and environment. 1+1+1=3
• Effect on non-target and beneficial insects/ microbes.
• Transgenes may escape through pollen to related plant species and may lead to
development of superweeds.
• GM crops may change the fundamental vegetable nature of plants as the 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 problem of antibiotic resistance in humans and
animal pathogens.
• May lead to a change in the evolutionary pattern.
• Any other relevant point

26 (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 1
proteins / protein sizes and amino acid sequence combinations of proteins.

(b) Proteome of a cell is dynamic because the biochemical machinery of a cell can be modulated
1
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 1
editing , alternative splicing.
(any other relevant point)
27
To use MALDI (Matrix Assisted Laser Desorption Ionisation) to volatalise and protonate
peptides and proteins : 3
• 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 on sample suspended /
dissolved in matrix.
• 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) The essential features that a vector should possess are :-
It must contain an origin of replication (ori) 1x2=2
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) . 1
These vectors consist of two types of origin of replication (ori) and selectable marker genes.

SECTION D

29 (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 1
response to treatment.
(ii) A single base difference in APOE gene is associated with Alzheimer’s disease / A 2
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 SNP’s vary in different 1
frequencies between populations.

OR

(iii) SNPs occur in both coding and non-coding regions of human genome. 1

30 (a)
(i) Contact Inhibition : Animal cells stop growing further as they reach the walls of a 1
container (confluency).

(ii) Properties of animal cells studied by oncologists to differentiate between normal
and cancerous cells are: 1
• Differences in growth patterns by using colony forming assay.

• Cancerous cells loose contact inhibition, pile on each other due to uncontrolled
growth, appear more rounded in shape, where as Normal cells show contact
inhibition, grow in monolayer mode, do not appear more rounded in shape.
(Any one) 1+1 =2

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

OR
2

(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,

SECTION E
31 (a)
(i) Primary metabolites are chemicals produced by plants required for basic metabolic processes,
for example sugars, lipids, amino acids, etc. 1+1=2
Some additional products produced in small amounts like alkaloids (used in medicine) , resins,
tannins, latex, etc which have a role in defense mechanism / protection of the plant against pest and
pathogens / feeding by animals are called secondary metabolites.

(ii) Any 3 from the following table:
Plant secondary metabolites produced Use
through cell and tissue culture
Artemisin Antimalarial (½+½)x3
=3
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
OR

(b)
(i) By developing genetically engineered rice (Golden rice) which is enriched in pro-
vitamin A (beta-carotenoids), by introducing three genes involved in biosynthetic

pathway for carotenoid under the control of endosperm specific promoter, so that gene 3
products (enzymes) are synthesised in the rice endosperm.

(ii) Because of deficiency of the essential amino acids. 1

(iii) Two essential amino acids which are deficient in pulses are methionine and tryptophan. ½+½=1

32 (a) (i) Fig.1. on page number 3 of “A Text book of Biotechnology” by CBSE

4

(For visually – impaired candidates only in lieu of Q. 32 (a) (i) )

(i) The four defined steps of RDT are :
2
a. Isolation of DNA fragment containing gene of interest (insert)
b. Generation of rDNA molecule by inserting DNA fragment into a carrier molecule
called vector/ plasmid.
c.Transfer of rDNA into host cell (Transformation)
d. Selection of host cells carrying rDNA and allowing them to multiply.

Scientists who were involved in generation of first recombinant DNA molecule : ½+½=1

Paul Berg, Herbert Boyer, Annie Chang and Stanley Cohen (Any Two)

Commercially produced products using this technology are:-
Human insulin (Humulin), Hepatitis B vaccine, Bt cotton, any other examples. ½+½=1
(Any Two)

(ii) Type II restriction enzymes recognise and cut DNA within a specific sequence
typically consisting of 4 to 8 basepairs (palindromic sequence , restriction site ). 1

OR

(b) (i) Polymerase Chain Reaction (PCR) Technique:-
1. Denaturation :- DNA is heated to a high temperature above 800 C which results 3
in DNA strand separation.
2. Annealing :- Each single strand anneals with the primer at a lower temperature
between 50-60 0 C.
3. 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
2
pathogens instead DNA from infected tissue is isolated for PCR technique.
Small quantities of DNA can be amplified by PCR.

33 a) (i) Conventional vaccines utilises heat inactivated bacteria or virus
or their surface proteins to generate immunity against various specific diseases. It 1+1= 2
has undesirable effects like fever ( caused due to incomplete inactivation of some of
the components ).
Recombinant vaccine is based on selected epitopes. It is safe to use.

(ii) The specific sequences of amino acids in the protein which stimulate immune
response are known as epitopes. 1

(iii) Advantages of preparing vaccines by using epitopes are that these vaccines
1+1=2
may provide optimal design, scope for micromanipulation, unhindered supply and
safety needed for an effective vaccine.
(Any 2)

OR

(b)
3
(i) BCAA help in increasing bio-availability of high complex carbohydrates intake
and they are absorbed by muscle cells for anabolic muscle building activity. During
exercise BCAA are released from the skeletal muscles, its carbon part is used as fuel
and nitrogen part is used to make alanine which goes to the liver where it is turned
into glucose for energy.
BCAA reduce muscle breakdown and act as energy source before and after exercise. It
delays exhaustion and are important for muscle growth.

1
(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 measure of growth expressed in terms of weight ½+½=1
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