CBSE Class 12 Biology 2025 question paper (57/7)

1. A.
   10 – 40 bp sized small sequences within the genes.
2. B.
   Short coding repetitive sequences region on the eukaryotic genome.
3. C.
   Short non-coding repetitive sequences forming a large portion of eukaryotic genome.
4. D.
   Regions of coding strand of DNA.

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1. A.
   Two sets of primers are required during polymerisation.
2. B.
   The process of replication is repeated multiple times to produce one billion copies.
3. C.
   Thermostable DNA polymerase is used for extension of primers.
4. D.
   Annealing is required to separate both the strands of template DNA.

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1. A.
   Cocaine is given to patients after surgery as it stimulates recovery.
2. B.
   Chewing tobacco lowers blood pressure and heart rate.
3. C.
   Barbiturates when given to criminals makes them tell the truth.
4. D.
   Morphine is often given to persons who have undergone surgery as a painkiller.

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1. A.
   (ii), (iii), (v), (vi), (iv), (i)
2. B.
   (ii), (v), (iii), (vi), (iv), (i)
3. C.
   (v), (ii), (iii), (vi), (i), (iv)
4. D.
   (ii), (iii), (vi), (iv), (v), (i)

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1. A.
   Homozygous sex chromosomes (ZZ) determine female sex in birds.
2. B.
   XO type of chromosomes determine male sex in grasshoppers.
3. C.
   XO condition in humans determines female sex.
4. D.
   Homozygous sex chromosomes (XX) produce male in Drosophila.

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1. A.
   Multicarpellary, Apocarpous
2. B.
   Bicarpellary, Apocarpous
3. C.
   Multicarpellary, Syncarpous
4. D.
   Bicarpellary, Syncarpous

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1. A.
   A single low, broad hump spread over the whole range
2. B.
   A single tall, narrow peak in the middle of the range
3. C.
   Two peaks of similar height with a dip between them
4. D.
   A curve rising gradually to a peak near the right end, then falling steeply

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1. A.
   Interferons – Secreted by virus-infected cells and protect non-infected cells from further viral infection.
2. B.
   Macrophages – Mucus-secreting cells that trap microbes entering into the body.
3. C.
   B-Lymphocytes – Produce antibodies in response to pathogens into blood to fight with them.
4. D.
   IgA – Present in colostrum in early days of lactation to protect infants from diseases.

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1. A.
   Pest-resistant crop variety
2. B.
   High nutritional value in grains
3. C.
   Drought-resistant crops
4. D.
   Production of insulin by rDNA technique

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1. A.
   80
2. B.
   70
3. C.
   10
4. D.
   90

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1. A.
   $8{\cdot}1$%
2. B.
   $12{\cdot}9$%
3. C.
   $7{\cdot}3$%
4. D.
   $5{\cdot}1$%

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1. A.
   Transgenic cow milk – Human beta-lactalbumin protein
2. B.
   ELISA – Antigen antibody interaction
3. C.
   Corn Borer – Cry II Ab gene
4. D.
   Cotton plant – Meloidegyne Incognitia

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Original bacterial plasmid
2. B.
   Modified bacterial plasmid
3. C.
   Viral genome
4. D.
   Transposon

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1. A.
   A single low, broad hump spread over the whole range
2. B.
   A single tall, narrow peak in the middle of the range
3. C.
   Two peaks of similar height with a dip between them
4. D.
   A curve rising gradually to a peak near the right end, then falling steeply

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1. A.
   Interferons – Secreted by virus-infected cells and protect non-infected cells from further viral infection.
2. B.
   Macrophages – Mucus-secreting cells that trap microbes entering into the body.
3. C.
   B-Lymphocytes – Produce antibodies in response to pathogens into blood to fight with them.
4. D.
   IgA – Present in colostrum in early days of lactation to protect infants from diseases.

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1. A.
   Unequal cells – a smaller haploid secondary oocyte and a larger diploid polar body
2. B.
   Unequal cells – a larger haploid secondary oocyte and a smaller haploid polar body
3. C.
   Unequal cells – a smaller diploid secondary oocyte and a larger haploid polar body
4. D.
   Equal cells – a haploid secondary oocyte and a haploid polar body

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1. A.
   All tall
2. B.
   50% tall, 50% dwarf
3. C.
   75% tall, 25% dwarf
4. D.
   25% tall, 75% dwarf

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1. A.
   Transgenic cow milk – Human beta-lactalbumin protein
2. B.
   ELISA – Antigen antibody interaction
3. C.
   Corn Borer – Cry II Ab gene
4. D.
   Cotton plant – Meloidegyne Incognitia

Tap an option to check your answer.

1. A.
   Cocaine is given to patients after surgery as it stimulates recovery.
2. B.
   Chewing tobacco lowers blood pressure and heart rate.
3. C.
   Barbiturates when given to criminals makes them tell the truth.
4. D.
   Morphine is often given to persons who have undergone surgery as a painkiller.

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1. A.
   $8{\cdot}1$%
2. B.
   $12{\cdot}9$%
3. C.
   $7{\cdot}3$%
4. D.
   $5{\cdot}1$%

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1. A.
   Streptococcus spp.
2. B.
   Trichoderma spp.
3. C.
   Bacillus thuringiensis
4. D.
   Saccharomyces cerevisiae

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1. A.
   Top Carnivore, Detritus, Secondary Consumer
2. B.
   Top Carnivore, Detritus, Primary Consumer
3. C.
   Scavenger, Grazing, Secondary Consumer
4. D.
   Scavenger, Grazing, Producer

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1. A.
   10 – 40 bp sized small sequences within the genes.
2. B.
   Short coding repetitive sequences region on the eukaryotic genome.
3. C.
   Short non-coding repetitive sequences forming a large portion of eukaryotic genome.
4. D.
   Regions of coding strand of DNA.

Tap an option to check your answer.

1. A.
   Multicarpellary, Apocarpous
2. B.
   Bicarpellary, Apocarpous
3. C.
   Multicarpellary, Syncarpous
4. D.
   Bicarpellary, Syncarpous

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   3'T$\downarrow$CCACCCGATGC5'
2. B.
   3'TCCA$\downarrow$CCCGATGC5'
3. C.
   3'TCCACCC$\downarrow$GATGC5'
4. D.
   3'TCCACCCGA$\downarrow$TGC5'

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1. A.
   Homozygous sex chromosomes (ZZ) determine female sex in birds.
2. B.
   XO type of chromosomes determine male sex in grasshoppers.
3. C.
   XO condition in humans determines female sex.
4. D.
   Homozygous sex chromosomes (XX) produce male in Drosophila.

Tap an option to check your answer.

1. A.
   Pest-resistant crop variety
2. B.
   High nutritional value in grains
3. C.
   Drought-resistant crops
4. D.
   Production of insulin by rDNA technique

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1. A.
   Formation of first polar body
2. B.
   Completion of Meiosis II
3. C.
   First Meiosis
4. D.
   Dissolution of zona pellucida

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1. A.
   $8{\cdot}1$%
2. B.
   $12{\cdot}9$%
3. C.
   $7{\cdot}3$%
4. D.
   $5{\cdot}1$%

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1. A.
   Transgenic cow milk – Human beta-lactalbumin protein
2. B.
   ELISA – Antigen antibody interaction
3. C.
   Corn Borer – Cry II Ab gene
4. D.
   Cotton plant – Meloidegyne Incognitia

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1. A.
   53%, 47%
2. B.
   47%, 53%
3. C.
   40%, 46%
4. D.
   22%, 16%

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1. A.
   a-iv, b-iii, c-ii, d-i
2. B.
   a-iii, b-iv, c-i, d-ii
3. C.
   a-ii, b-i, c-iv, d-iii
4. D.
   a-i, b-ii, c-iii, d-iv

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1. A.
   Multicarpellary, Apocarpous
2. B.
   Bicarpellary, Apocarpous
3. C.
   Multicarpellary, Syncarpous
4. D.
   Bicarpellary, Syncarpous

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1. A.
   Detritus, Grazing
2. B.
   Grazing, Detritus
3. C.
   Detritus, Detritus
4. D.
   Grazing, Grazing

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1. A.
   Two sets of primers are required during polymerisation.
2. B.
   The process of replication is repeated multiple times to produce one billion copies.
3. C.
   Thermostable DNA polymerase is used for extension of primers.
4. D.
   Annealing is required to separate both the strands of template DNA.

Tap an option to check your answer.

1. A.
   Cocaine is given to patients after surgery as it stimulates recovery.
2. B.
   Chewing tobacco lowers blood pressure and heart rate.
3. C.
   Barbiturates when given to criminals makes them tell the truth.
4. D.
   Morphine is often given to persons who have undergone surgery as a painkiller.

Tap an option to check your answer.

1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

Tap an option to check your answer.

1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

Tap an option to check your answer.

1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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1. A.
   Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
2. B.
   Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
3. C.
   Assertion (A) is true, but Reason (R) is false.
4. D.
   Assertion (A) is false, but Reason (R) is true.

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