Applications of Genetic Engineering Questions and Answers

Q: Arabidopsis AtNHX1 gene encodes a tonoplast Na+/H+ antiporter used to develop transgenic plants to improve :

AtNHX1 is used to improve salinity tolerance.The AtNHX1 protein exchanges protons for sodium ions across the tonoplast, moving Na+ from the cytoplasm into the vacuole. Sequestering sodium in the vacuole keeps it away from cytoplasmic enzymes and helps the cell maintain osmotic balance. Overexpressing AtNHX1 in Arabidopsis allowed plants to grow in about 200 mM sodium chloride, and the gene has since been used in tomato, canola and other crops for the same purpose.Drought tolerance, pest resistance and pathogen resistance are engineered with other genes (for example osmolyte or dehydrin genes for drought, Bt toxins for insects, resistance genes for pathogens), so they do not describe the purpose of a sodium-proton antiporter.

Q: For developing transgenic mustard variety DMH-11 Bar, Barnase and Barstar genes were obtained from :

The keyed answer is Bacillus amyloliquefaciens.The hybrid mustard DMH-11, developed at Delhi University, uses the barnase-barstar system for hybrid seed production. Barnase, a ribonuclease expressed in the tapetum, makes the male line sterile, and barstar, its specific inhibitor, restores fertility in the hybrid. Both genes come from the soil bacterium Bacillus amyloliquefaciens.The third gene, bar, which confers tolerance to the herbicide glufosinate and is used as a selectable marker, comes from Streptomyces hygroscopicus, which is not among the options; of those given, only B. amyloliquefaciens supplied genes. B. thuringiensis is the source of Bt insecticidal toxins, Agrobacterium tumefaciens is the vector used for gene transfer, and Erwinia uredovora supplied the crtI gene of Golden Rice.

Q: In golden rice, the gene phytoene desaturase (crtl) was obtained from :

The crtI gene came from Erwinia uredovora (printed 'uredovera').Golden rice makes beta-carotene in the endosperm by adding two genes: phytoene synthase (psy), from daffodil (Narcissus pseudonarcissus) in the original version and from maize in Golden Rice 2, and the bacterial phytoene desaturase crtI from Erwinia uredovora, which carries out several desaturation steps in one.So Narcissus and Zea mays supplied the phytoene synthase, not crtI, and Oryza sativa is the rice itself, which lacks an active pathway in the endosperm.

Q: The purification and characterization of insecticidal protein/s produced by Bacillus thuringiensis during the exponential phase of growth was carried out. Protein fractions were purified both from cell pellet (P) as well as from culture supernatant (S). The purified toxin proteins were heated at indicated temperatures and then used in bioassays against first instar larvae of black cut worm. Percent mortality of the larvae when feeded with toxin proteins were as follows :Temperature °CMortality % Toxin Protein (P)Mortality % Toxin Protein (S)2810050377550506850654050851050Boiled030Which of the following is not true for the given data ?

The statement that is not true is Toxin [S] is thermolabile.Toxin (S) gives the same 50% mortality from 28 °C right up to 85 °C, and still kills 30% after boiling. Its activity is hardly affected by heat, so it is thermostable, the opposite of thermolabile.The other statements fit the data. Toxin (P) falls from 100% mortality at 28 °C to 10% at 85 °C and 0 after boiling, so heat clearly harms it. Both proteins kill larvae, with different stability. And at the moderate temperatures where larvae feed, toxin (P) is the more potent, with 100% against 50% mortality at 28 °C.

Arabidopsis AtNHX1 gene encodes a tonoplast Na⁺/H⁺ antiporter used to develop transgenic plants to improve :

A.drought tolerance
B.salinity tolerance
C.pest resistance
D.pathogen resistance

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: B

AtNHX1 is used to improve salinity tolerance.

The AtNHX1 protein exchanges protons for sodium ions across the tonoplast, moving Na⁺ from the cytoplasm into the vacuole. Sequestering sodium in the vacuole keeps it away from cytoplasmic enzymes and helps the cell maintain osmotic balance. Overexpressing AtNHX1 in Arabidopsis allowed plants to grow in about 200 mM sodium chloride, and the gene has since been used in tomato, canola and other crops for the same purpose.

Drought tolerance, pest resistance and pathogen resistance are engineered with other genes (for example osmolyte or dehydrin genes for drought, Bt toxins for insects, resistance genes for pathogens), so they do not describe the purpose of a sodium-proton antiporter.

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For developing transgenic mustard variety DMH-11 Bar, Barnase and Barstar genes were obtained from :

A.Bacillus amyloliquefaciens
B.Bacillus thuringiensis
C.Agrobacterium tumefaciens
D.Erwinia uredovora

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: A

The keyed answer is Bacillus amyloliquefaciens.

The hybrid mustard DMH-11, developed at Delhi University, uses the barnase-barstar system for hybrid seed production. Barnase, a ribonuclease expressed in the tapetum, makes the male line sterile, and barstar, its specific inhibitor, restores fertility in the hybrid. Both genes come from the soil bacterium Bacillus amyloliquefaciens.

The third gene, bar, which confers tolerance to the herbicide glufosinate and is used as a selectable marker, comes from Streptomyces hygroscopicus, which is not among the options; of those given, only B. amyloliquefaciens supplied genes. B. thuringiensis is the source of Bt insecticidal toxins, Agrobacterium tumefaciens is the vector used for gene transfer, and Erwinia uredovora supplied the crtI gene of Golden Rice.

Discuss in Forum

In golden rice, the gene phytoene desaturase (crtl) was obtained from :

A.Narcissus species
B.Erwinia uredovera
C.Zea mays
D.Oryza sativa

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: B

The crtI gene came from Erwinia uredovora (printed 'uredovera').

Golden rice makes beta-carotene in the endosperm by adding two genes: phytoene synthase (psy), from daffodil (Narcissus pseudonarcissus) in the original version and from maize in Golden Rice 2, and the bacterial phytoene desaturase crtI from Erwinia uredovora, which carries out several desaturation steps in one.

So Narcissus and Zea mays supplied the phytoene synthase, not crtI, and Oryza sativa is the rice itself, which lacks an active pathway in the endosperm.

Discuss in Forum

The purification and characterization of insecticidal protein/s produced by Bacillus thuringiensis during the exponential phase of growth was carried out. Protein fractions were purified both from cell pellet (P) as well as from culture supernatant (S). The purified toxin proteins were heated at indicated temperatures and then used in bioassays against first instar larvae of black cut worm. Percent mortality of the larvae when feeded with toxin proteins were as follows :

Temperature °C	Mortality % Toxin Protein (P)	Mortality % Toxin Protein (S)
28	100	50
37	75	50
50	68	50
65	40	50
85	10	50
Boiled	0	30

Which of the following is not true for the given data ?

A.Toxin [S] is thermolabile
B.Higher temperatures adversely affect activity of toxin (P)
C.Both toxins are insecticidal although with varying stability
D.Insecticidal activity of toxin (P) is better than toxin (S)

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: A

The statement that is not true is Toxin [S] is thermolabile.

Toxin (S) gives the same 50% mortality from 28 °C right up to 85 °C, and still kills 30% after boiling. Its activity is hardly affected by heat, so it is thermostable, the opposite of thermolabile.

The other statements fit the data. Toxin (P) falls from 100% mortality at 28 °C to 10% at 85 °C and 0 after boiling, so heat clearly harms it. Both proteins kill larvae, with different stability. And at the moderate temperatures where larvae feed, toxin (P) is the more potent, with 100% against 50% mortality at 28 °C.

Discuss in Forum

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