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57. A group of researchers are testing two new agents, M1 and M2 for their efficacy in selecting transgenic plants. When they performed tissue culture experiments using three explants, A, B, and C without Agrobacterium transformation, and selected the regenerated plants on M1 and M2, the following regeneration frequencies were obtained. Based on the above data, which one of the following conclusions is INCORRECT? (1) M2 is a stronger selection agent than M1 for explant types A and B. (2) A concentration of 100 mg/L of M1 and 15 mg/L of M2 can be used for selection of transformed cells using explant type A. (3) Among the three explants, type C is least suitable at the tested concentrations of M1 and M2 (4) Use of M1 with explant type B is the most ideal combination for selection of transformants.

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Interpreting selection-agent efficacy and explant suitability from regeneration data

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November 28, 2025
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A group of researchers are testing two new agents, M1 and M2 for their efficacy in selecting transgenic plants. When they performed tissue culture experiments using three explants, A, B, […]

56. RNA silencing is an important strategy to control viral infection in plants. The following statements were made regarding RNA silencing. A. It is driven by small interfering RNA (SiRNA) derived from double-stranded form of viral RNA. B. siRNA requires RISC for it function. C. Many plant viruses encode proteins that act as suppressors of RNA silencing. D. Viral P19 protein activates RNA induced silencing complex Which one of the following combination of statements is correct? (1) A, B and C (2) B, C and D (3) A, C and D (4) A, B and D

CSIR NET Life Science Previous Year Questions and Solution on applied biology

How RNA silencing controls plant viruses and the role of P19

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November 28, 2025
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RNA silencing is an important strategy to control viral infection in plants. The following statements were made regarding RNA silencing. A. It is driven by small interfering RNA (SiRNA) derived […]

55. In an attempt to increase the yield of a commercially important enzyme from natural isolate several strategies were adopted as follows: (A) Genome was selectively modified to increase yield. (B) Reappraisal of culture requirements of the modified organism to increase yield. (C) Induced mutants were screened and selected for organism synthesizing improved levels of the enzyme. (D) Organism was genetically modified, so that it produces a factor that enhances stability of the enzyme. Which one of the following options represents strategies that are appropriate for the purpose? (1) A, B, C and D (2) B and C only (3) A, C and D only (4) A and B only

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Strategies to increase yield of a commercially important enzyme from a natural isolate

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November 28, 2025
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In an attempt to increase the yield of a commercially important enzyme from natural isolate several strategies were adopted as follows: (A) Genome was selectively modified to increase yield. (B) […]

54. The figure below depicts a hypothetical scheme for synthesizing a target product in plants. A, B, and C are the precursors of a target product D, whereas E is a by-product. The key enzymes of the pathway are indicated as E1—E6. To enhance the levels of target product D, following strategies were tested: (A) Enhancing the activity of the enzyme E5 by over- expression and/or protein engineering. (B) Enhancing the activity of the enzyme E4 by over- expression and/or protein engineering. (C) Enhancing the levels of C. (D) Blocking the activity of E6 by RNA-interference or CRISPR/Cas-mediated knockout. Which of the above mentioned strategies are likely to provide the maximum enhancement of the target product compared to the by-product, if no feedback regulation exists for any of the enzymes in the pathway? (1) A and B (2) B and C (3) C and D (4) A and D

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Metabolic engineering strategies to maximize target product over by‑product

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November 28, 2025
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The figure below depicts a hypothetical scheme for synthesizing a target product in plants. A, B, and C are the precursors of a target product D, whereas E is a […]

53. Engineering of metabolic pathways in plants can be achieved by introduction and overexpression of appropriate candidate gene(s) using transgenic technology. The figure given below represents a biochemical pathway in plants where a precursor molecule 'A' is converted in to products 'T' and 'X' through a series of enzymatic reactions. Enzymes 1-5 are involved in this pathway. Scientists attempted to increase the levels of 'X' by introducing additional copy of the gene for enzyme '5' under transcriptional control of a strong constitutive promoter. However, the developed transgenic plants did not display a proportionate increase in the level of 'X'. The following statements were proposed for explaining the above results: (A) Enzyme '4' has greater affinity for D than enzyme '3' (B) Feedback inhibition of enzyme '5' by compound X (C) Substrate limitation for enzyme '5' Which of the above statement could represent probable reasons for NOT obtaining proportionate increase in the amount of 'X' in the transgenic plants? (1) Only C (2) Only A and B (3) Only A (4) A, B and C

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Why does overexpressing a pathway enzyme not give proportional product increase?

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November 28, 2025
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Engineering of metabolic pathways in plants can be achieved by introduction and overexpression of appropriate candidate gene(s) using transgenic technology. The figure given below represents a biochemical pathway in plants […]

52. Given below are a few statements on technologies/concepts related to development of transgenic plants: A. Frequency of genetic transformation is influenced only by the genes of Agrobacterium and not by those of the host plants. B. Transgenic plants containing a single copy of the transgene are preferred over those that contain multiple transgene copies for subsequent genetic analysis. C. Super virulent strains of Agrobacterium can be generated by increasing the copy number of virulence genes. D. A non conditional negative selection marker has to be necessarily used with a strong constitutive promoter for the development of transgenic plants. Which one of the following options represents a combination of all INCORRECT statements? (1) A and D only (2) C only (3) B and C only (4) D only

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Identifying incorrect statements about transgenic plant development

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November 28, 2025
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Given below are a few statements on technologies/concepts related to development of transgenic plants: A. Frequency of genetic transformation is influenced only by the genes of Agrobacterium and not by […]

51. Following statements were given regarding factors influencing variation in expression levels of transgene in transgenic plants: A. Difference in restriction enzyme sites within the T- DNA. B. Difference in copy number of the transgene. C. Variations in site of integration of the T- DNA within the plant genome. D. Presence of multiple promoters within the T-DNA region. Which one of the following options represents a combinations of statements that would NOT lead to variations in transgene expression levels in transgenic plants generated using the same T-DNA/ binary vector? (1) A and C only (2) B only (3) C and D only (4) A and D only

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Which factors do not change transgene expression when using the same T‑DNA vector?

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November 28, 2025
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Following statements were given regarding factors influencing variation in expression levels of transgene in transgenic plants: A. Difference in restriction enzyme sites within the T- DNA. B. Difference in copy […]

50. An experiment was performed to introduce a transgenic trait in a crop plant by Agrobacterium - mediated transformation using a transgene construct in which the transgene was expressed using the CaMV 355 promoter. It was observed that expression levels of the transgenic protein were very low in all transgenic plants while transgene mRNA levels were high and variable among different plants. Further, different transgenic lines contained different numbers of the T- DNA insert. The following statements were made to explain the above observation: (A) Variations in the number of T-DNA inserts in different transgenic plants is due to more number of host cells getting infected with the T- DNA (A) Low expression levels of the transgenic protein in all transgenic plants could be due to codon usage variations between the host plant and the heterologous source of the transgene (B) The coding sequence of the transgene contained sequences that destabilized the transgene mRNA (C) Variation in copy number of T-DNA in different transgenic plants is due to variation in the promoter used to express the transgene. Which one of the following options represents all correct statements? (1) A only (2) B and C (3) A and D (4) B only

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Why can a CaMV 35S-driven transgene show high mRNA but low protein?

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November 28, 2025
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An experiment was performed to introduce a transgenic trait in a crop plant by Agrobacterium – mediated transformation using a transgene construct in which the transgene was expressed using the […]

49. Given below is a figure representing expression levels of transgenic protein in ten independent transgenic plants generated using the same transformation vector by Agrobacterium-mediated transformation. Given below are a few statements to explain the above data: A. Plant nos. 4, 9 and 10 that show high expression levels of the transgene would necessarily contain multiple copies of the transgene. B. Plant nos. 2 and 7 contain mutations in the coding sequence of the transgene in the construct. C. The transgenic plants may contain varying number of transgene copies inserted at different locations in the host genome. D. The host genome has no role in influencing expression levels of the transgene. E. The stability of the transgenic mRNA and its translatability would not be different among the independent transgenic plants. Which one of the following options represents all correct statements? (1) A and D only (2) B and C only (3) C and E only (4) A, D and E only

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Why do independent transgenic events show different expression levels?

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November 28, 2025
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Given below is a figure representing expression levels of transgenic protein in ten independent transgenic plants generated using the same transformation vector by Agrobacterium-mediated transformation. Given below are a few […]

48. Agrobacterium mediated transformation was used to generate transgenic plants using a construct with a selection marker gene "X" and a passenger gene "Y". Expression levels of "Y" protein in eight independent transgenic plants are given below The following could represent probable reasons for the observed variability in transgene expression levels (A) Position effects on passenger gene (B) Transgene silencing of the marker gene (C) Variation in copy number of passenger gene (D) mRNA instability of marker gene Which one of the following combinations of above statements is correct? (1) A and C (2) C and D (3) B and D (4) A and B

CSIR NET Life Science Previous Year Questions and Solution on applied biology

Why do independent transgenic plants show variable transgene expression?

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November 28, 2025
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Agrobacterium mediated transformation was used to generate transgenic plants using a construct with a selection marker gene “X” and a passenger gene “Y”. Expression levels of “Y” protein in eight […]

Interpreting selection-agent efficacy and explant suitability from regeneration data

How RNA silencing controls plant viruses and the role of P19

Strategies to increase yield of a commercially important enzyme from a natural isolate

Metabolic engineering strategies to maximize target product over by‑product

Why does overexpressing a pathway enzyme not give proportional product increase?

Identifying incorrect statements about transgenic plant development

Which factors do not change transgene expression when using the same T‑DNA vector?

Why can a CaMV 35S-driven transgene show high mRNA but low protein?

Why do independent transgenic events show different expression levels?

Why do independent transgenic plants show variable transgene expression?

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