Class 12 CBSE Biology Specimen Question 2024
Maximum Marks: 80
Time Allowed: Three hours
(i) All questions are compulsory.
(ii) The question paper has five sections and 33 questions. All questions are compulsory.
(iii) Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each; Section– C
has 7 questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each; and
Section–E has 3 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.
class 12 CBSE Biology Specimen Question Paper 2024
SECTION A
Question 1
Remnants of nucellus are persistent during seed development in:
a) pea
b) groundnut
c) wheat
d) black pepper
Solution
The wall layer of microsporangium which nourishes the pollen grain is:
a) epidermis
b) endothecium
c) middle layers
d) tapetum
Solution
A short piece of DNA, having 20 base pairs, was analyzed to find the number of
nucleotide bases in each of the polynucleotide strands. Some of the results are
shown in the table.
How many nucleotides containing Adenine were present in strand 2?
a) 2
b) 4
c) 5
d) 7
Solution
In a certain species of insects, some have 13 chromosomes, and the others have
14chromosomes.The 13 and 14 chromosome bearing organisms are
a) males and females, respectively
b) females and males, respectively
c) all males
d) all females
Solution
At a particular locus, the frequency of allele A is 0.8 and that of allele a is 0.2.
What would be the frequency of heterozygotes in a random mating population at
equilibrium?
a) 0.32
b) 0.16
c) 0.24
d) 0.48
Solution
Variations caused due to mutations are
a) random and directionless
b) random and directional
c) random and small
d) random, small and directional
Solution
What is the smallest part of a DNA molecule that can be changed by a point
mutation?
a) Oligonucleotide
b) Codon
c) Gene
d) Nucleotide
Solution
A patient was advised to have a kidney transplant. To suppress the immune
reaction, the doctor would administer him:
a) statins produced from Monascus purpureus
b) statins produced from Streptococcus thermophilus
c) cyclosporin A produced from Trichoderma polysporum
d) cyclosporin A produced from Clostridium butylicum
Solution
The main objective of production of pest resistant GM crops is to
a) encourage eco-friendly pesticides
b) reduce pesticide accumulation in food chain
c) eliminate pests from the field without the use of manual labour
d) retain maximum nutritional content in the crop that would be otherwise
consumed by pest
Solution
Observe the contents 1,2,3 and 4 of soil samples A,B and C shown in the graph. If
the temperature and soil moisture of all soil samples are identical, which soil
sample (s) will show faster decomposition?
a) Soil Sample A
b) Soil Sample B
c) Soil Samples A and B both
d) Soil Sample C
Solution
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 A and R are true and R is the correct explanation of A.
b) Both A and R are true and R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true
Assertion: Primary endosperm nucleus is diploid.
Reason: It is the product of double fertilisation.
Solution
Assertion:Ribosomal RNA is synthesized in the nucleus of the cell.
Reason: It is translated with the enzyme RNA polymerase III.
Solution
Assertion: Smoking can raise blood pressure and increase heart rate.
Reason: Nicotine stimulates adrenal glands to release adrenaline and noradrenaline into the blood
circulation, both of which raise blood pressure and
increase heart rate
Solution
Assertion: PCR is a powerful technique to identify genetic disorders.
Reason: PCR can detect mutations in low amounts of DNA
Solution
SECTION B
Question 17
The diagram below shows the sequence of amino acids in part of a haemoglobin
molecule.
a) If the base T* was substituted with A, how would it affect the haemoglobin
chain?
b) Name the condition and the effects associated with the above substitution
Solution
The graph given below indicates the administration of the first (L) and second dose
(M) of a vaccine. The corresponding response of the body is indicated by X and Y.
Interpret the graph and explain the reason for such a response shown by the
body.
Solution
The image below shows the result of plating bacteria in chromogenic medium after
incorporating the gene of interest in plasmid. Some plates had blue colonies; some
plates had white colonies. A single bacterium extracted from Plate I,II,III is shown
below:
On the basis of your observations
a) Identify the plate(s) which is/are white. Give a reason.
b) Identify the plate(s) which is/are blue. Give a reason
Solution
Biomass of a standing crop of phytoplankton is 4 kg/m2 which supports a large
standing crop of zooplankton having a biomass 11 kg/m2
. This is consumed by
small fishes having biomass 25 kg/m2 which are then consumed by large fishes with
the biomass 37 kg/m2
Draw an ecological pyramid indicating the biomass at each stage and also name the
trophic levels. Mention whether it is an upright or inverted pyramid.
OR
Use the information provided in the table given below to answer the following
questions:
a) Calculate the gross primary productivity.
b) Analyze the trend in the Net Production from Producers to Top
Carnivore. Give a reason for your observation.
Solution
SECTION C
Question 22
The figure given below shows 3 sperms A, B and C.
a) Which one of the three sperms will gain entry into the ovum?
b) Describe the associated changes induced by it on P and Q
Solution
Explain the phases in embryonic development from the morula stage till the establishment of pregnancy in a human female.
Solution
A pregnant human female was advised to undergo MTP. It was diagnosed that the
fetus she was carrying had developed from a zygote having 45 chromosomes with
only one X chromosome.
a) What is this condition called and how does it arise?
b) Why was she advised to undergo MTP?
Solution
The graphs below show three types of natural selection. The shaded areas
marked with arrows show the individuals in the population which are not
selected. The dotted vertical lines show the statistical means.
a) What names are given to the types of selection shown in graphs A, B
and C.
b) After the selection has operated for several generations in the above
populations indicated as Graph A, B and C, graphically illustrate the probable
results
Solution
Remnants of nucellus are persistent during seed development in:
a) pea
b) groundnut
c) wheat
d) black pepper
Solution
A farmer grew 2 varieties of corn crop in field A and B. He grew normal corn
crops in field A and GM corn crops in field B. He observed corn borers attacked
only in field A. To control it, spores of Bt were sprayed in field A.
a) Name the gene in the spores responsible for the control of this pest.
b) What effect will the spores of Bt have on the insect pest?
c) How has field B developed resistance against this pest?
OR
Lipoprotein lipase deficiency (LPLD)is a genetic disorder in which a person has a
defective gene for lipase. This leads to high triglycerides, stomach pain, fat
deposits under the skin. It may eventually affect the liver, pancreas and may also
cause diabetes. The disorder occurs if a child acquires defective genes from both parents (autosomal
recessive). ERT (enzyme replacement treatment) is one of the
treatments offered to patients with LPLD.
a) (i) What procedure is followed in ERT?
(ii) What could be one possible drawback of ERT?
b) How can LPLD be treated using Biotechnology? Elaborate
Solution
Give three reasons as to why the prokaryotes are not given any figures for their diversity by the ecologists.
Solution
SECTION D
Q. No. 29 and 30 are case-based questions. Each question has 3 subparts with internal choice in one subpart.
The structure below shows pUC18 which is similar to pBR322 in its function.
However, they differ in some of their restriction sites and number of ori. The ori
number for pBR322 is approximately 20.
a) How are puc18 and pBR322 used in biotechnological studies?
OR
What will be the impact if oriin the above structure gets damaged?
b) The lac z gene has many recognition sites. Study the segment of DNA
given below and answer the questions
5’... ATC GTA AAG CTT CAT…3’
3’... TAG CAT TTC GAA GTA…5’
i) Applying your knowledge of palindrome sequences identify and mark
the possible region where the restriction enzyme X will act.
ii) Restriction enzyme Y was used to extract gene of interest from a plant.
This gene needs to be inserted in the given DNA segment which has
been treated with restriction enzyme X. Will there be a successful
recombination? Explain with a reason.
c) Which one of the two (pUC18 and pBR322) would you prefer for
biotechnological studies? Justify.
Solution
Observe the graph given below.
The graph represents inter-specific interaction between two species of Paramecia
competing for the same resource in a culture medium. Paramecium caudatum and
Paramecium aurelia were grown in separate cultures as well as in mixed cultures. It
was found that each species grew in numbers according to the logistic equation.
a) Which species is competitively superior? Support it with the data provided in
the graph.
b) State the underlying principle for the above result and name the scientist
associated with this principle.
c) Explain the mechanism in which two or more species competing with each
other can co - exist.
OR
Graphs A and B shown below depict interaction of two species. Which graph
indicates Mutualism? Give reason.
Solution
SECTION E
Question 31
Placed below are case studies of some couples who were not able to have
kids. These couples are not ready for adoption or taking gametes from
donors. After thoroughly examining the cases, which Assisted
Reproductive Technology will you suggest to these couples as a medical
expert? Explain briefly with justification of each case.
OR
Given below are certain situations. Analyse the situation and suggest the
name of suitable contraceptive device along with mode of action.
Solution
Given below is a stretch of DNA showing the coding strand of a
structural gene of a transcription unit?
5’--ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA
TAA—3’
a) Write the corresponding template strand and the mRNA strand that
will be transcribed, along with its polarity.
b) If GUA of the transcribed mRNA is an intron, depict the sequence
involved in the formation of mRNA /the mature processed hnRNA
strand.
i. In a bacterium
ii. In humans
c) Upon translation, how many amino acids will the resulting polypeptide
have? Justify.
OR
In shorthorn cattle, the coat colours red or white are controlled by a
single pair of alleles. A calf which receives the allele for red coat from its
mother and the allele for white coat from its father is called a 'roan'. It has
an equal number of red and white hairs in its coat.
a) Is this an example of codominance or of incomplete dominance?
b) Give a reason for your answer.
c) With the help of genetic cross explain what will be the consequent
phenotype of the calf when
i. red is dominant over white
ii. red is incompletely dominant.
Solution
Explain the role of Primary and Secondary Lymphoid organs with the help
of suitable examples.
OR
With the help of a flow chart illustrate how an infected animal cell can
survive while viruses are being replicated or released.
Solution
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