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Biology 57-5-3 2025-2026 Science (English Medium) Class 12 Question Paper Solution

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Biology [57-5-3]
Marks: 70 CBSE
Science (English Medium)

Academic Year: 2025-2026
Date & Time: 27th March 2026, 10:30 am
Duration: 3h
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Note:

  1. Please check that this question paper contains 23 printed pages.
  2. Q.P. Code given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate.
  3. Please check that this question paper contains 33 questions.
  4. Please write down the Serial Number of the question in the answer-book at the given place before attempting it.
  5. 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m, the candidates will read the question paper only and will not write any answer on the answer-book during this period.

General Instructions:

Read the following instructions very carefully and strictly follow them:

  1. This question paper contains 33 questions. All questions are compulsory.
  2. Question paper is divided into five sections – Sections A, B, C, D, and E.
  3. Section A – questions number 1 to 16 are Multiple Choice Type questions. Each question carries 1 mark.
  4. Section B – questions number 17 to 21 are Very Short Answer Type questions. Each question carries 2 marks.
  5. Section C – questions number 22 to 28 are Short Answer Type questions. Each question carries 3 marks.
  6. Section D – questions number 29 and 30 are Case-Based questions. Each question carries 4 marks. Each question has subparts with internal choice in one of the subparts.
  7. Section E – questions number 31 to 33 are Long Answer Type questions. Each question carries 5 marks.

Section - A
Questions no. 1 to 16 are Multiple Choice Type Questions, carrying 1 mark each. Choose the best option.
[1]1.

The foetal ejection reflex in humans triggers the release of ______ hormone from ______.

oxytocin, foetal pituitary

oxytocin, maternal pituitary

human chorionic gonadotropin, placenta

progesterone, corpus luteum

Concept: undefined - undefined
Chapter:
[1]2.

Match the IUDs in Column I with suitable example in Column II.

  Column I   Column II
a. Non-medicated i. Lippes loop
b. Copper releasing ii. LNG-20
c. Hormone releasing iii. Multiload 375

a - iii, b - ii, c - i

a - i, b - ii, c - iii

a - i, b - iii, c - ii

a - ii, b - i, c - iii

Concept: undefined - undefined
Chapter:
[1]3.

In Pisum sativum, the flower colour may be violet (V) or white (v). What proportion of the offspring in a cross of “VV × vv” would be expected to be violet?

25%

50%

75%

100%

Concept: undefined - undefined
Chapter:
[1]4.

Arrange the following in the correct sequence of their evolution and select the correct option:

  1. Seaweed
  2. Invertebrates
  3. Jawless fish

(i), (ii), (iii)

(i), (iii), (ii)

(ii), (iii), (i)

(ii), (i), (iii)

Concept: undefined - undefined
Chapter:
[1]5.

If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is ______.

Sex-linked recessive

Autosomal dominant

Sex-linked dominant

Autosomal recessive

Concept: undefined - undefined
Chapter:
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[1]6.

A DNA molecule is 160 base pairs long. It has 30% Guanine. How many Adenine bases are present in this DNA molecule?

48

64

96

192

Concept: undefined - undefined
Chapter:
[1]7.

A doctor identifies symptoms of nasal congestion, headache, sore throat, hoarseness, and cough in a patient. The conclusion is that the patient is infected by a pathogen ______.

Plasmodium

Adenovirus

Salmonella

Rhinovirus

Concept: undefined - undefined
Chapter:
[1]8.

Which type of selection is industrial melanism observed in moth, Biston betularia?

Stabilising

Directional

Disruptive

Artificial

Concept: undefined - undefined
Chapter:
[1]9.

C-peptide of human insulin is ______.

A part of mature insulin molecule

Responsible for the formation of disulphide bridges

Removed during maturation of pro-insulin to insulin

Responsible for its biological activity.

Concept: undefined - undefined
Chapter: [8] Microbes in Human Welfare
[1]10.

Given below is the restriction site of a restriction endonuclease Pst-I and the cleavage sites on a DNA molecule.

\[\ce{5' C - T - G - C - A \overset{\downarrow}{-}{G 3'}}\]

\[\ce{3' G\underset{\uparrow}{-} A - C - G - T - C 5'}\]

Choose the option that gives the correct resultant fragments by the action of the enzyme Pst-I.

5' C - T - G C - A - G 3'
3' G - A - C - G - T C 5'
5' C - T G - C - A - G 3'
3' G - A - G - C T - C 5'
5' C - T - G - C A - G 3'
3' G - A - C - G T - C 5'
5' C - T - G - C - A G 3'
3' G A - C - G - T - C 5'
Concept: undefined - undefined
Chapter: [9] Biotechnology - Principles and Processes
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[1]11.

Which of the following fish led to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in Lake Victoria of East Africa?

Catla Catla

Dogfish

Nile Perch

African Catfish

Concept: undefined - undefined
Chapter:
[1]12.

Cattle or goats are never seen browsing on the weed, Calotropis. Select the correct option for the reason.

The plant produces highly poisonous tannins.

The plant produces quinine, which is bitter in taste.

The plant produces the poisonous chemical, cardiac glycoside.

The plant bears prickles.

Concept: undefined - undefined
Chapter:
For Questions number 13 to 16, two statements are given - one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
[1]13.

Assertion (A): Repetitive sequences make up a very large portion of the human genome.

Reason (R): Repetitive sequences do not have direct coding functions in the genome.

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

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

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

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

Concept: undefined - undefined
Chapter:
[1]14.

Assertion (A): The embryo with 8 to 16 blastomeres is called a morula.

Reason (R): The morula continues to divide and transform into trophoblast.

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

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

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

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

Concept: undefined - undefined
Chapter:
[1]15.

Assertion (A): The use of chitinase enzyme is necessary for the separation of DNA from yeast cells but not in the case of Spirogyra.

Reason (R): Fungal cell wall is made up of fungal chitin.

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

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

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

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

Concept: undefined - undefined
Chapter:

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