Question

 Match the organism with its use in biotechnology. [NEET (Sep.) 2020]

Select the correct option.
     A B C D
(a) 4 3 1 2

(b) 3 2 4 1

(c) 3 4 1 2

(d) 2 4 3 1

Answer/Explanation

Ans. (a)

The correct option is (a). It can be explained as follows Bacillus thuringiensis is a source of Cry proteins. Thermus aquaticus is a source of thermostable DNA polymerase (Taq polymerase) used in PCR. Agrobacterium tumefaciens is a cloning vector. The construction of 1st recombinant DNA molecule was performed using native plasmid of Salmonella typhimurium.

Question

RNA interference is used for which of the following purposes in the field of biotechnology? [NEET (Oct.) 2020]

(a) to develop a plant tolerant to abiotic stresses

(b) to develop a pest resistant plant against infestation by nematode

(c) to enhance the mineral usage by the plant

(d) to reduce post harvest losses

Answer/Explanation

Ans. (b)

RNA interference is used to develop a pest resistant plant against infestation by nematode. RNA interference takes place in all eukaryotic organisms as a method of cellular defence. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).

Question

 Bt cotton variety that was developed by the introduction of toxin gene of Bacillus thuringiensis $(B t)$ is resistant to [NEET (Sep.) 2020]

(a) fungal diseases

(b) plant nematodes

(c) insect predators

(d) insect pests

Answer/Explanation

Ans. (d)

The correct option is (d). It can be explained as follows Bt cotton is resistant to cotton bollworm (insect pest). cry $\mid A c$ and cry II Ab genes have been introduced in cotton to protect it from cotton bollworm. This makes Bt cotton as biopestic.

Question

 If an agricultural field is liberally irrigated for a prolonged period of time, it is likely to face problem of [NEET (Odisha) 2019]

(a) metal toxicity

(b)alkalinity

(c) acidity

(d) salinity

Answer/Explanation

Ans. (d)

Salinity of soil is a problem faced by farmers if they liberally irrigate agricultural field for a prolonged period of time. Irrigation salinity is the accumulation of salts in the topsoil under irrigation. It is caused by over irrigation of agricultural land, inefficient water use, poor drainage and the irrigation of unsuitable and leaky soils.

Question

 Which part of the tobacco plant is infected by Meloidegyne incognitia? [NEET 2016, Phase II]

(a) Leaf

(b) Stem

(c) Root

(d) Flower

Answer/Explanation

Ans. (c)

Meloidegyne incognitia is a nematode, which infects roots of tobacco plant and results in root knot disease.

Question

 Golden rice is a genetically modified crop plant where the incorporated gene is meant for biosynthesis of [CBSE AIPMT 2015]

(a) vitamin-B

(b) vitamin-C

(c) omega 3

(d) vitamin-A

Answer/Explanation

Ans. (d)

Golden rice is a variety of rice produced through genetic engineering to biosynthesise $\beta$-carotene, a precursor of vitamin-A, in the edible parts of rice.

Question

The introduction of tDNA into plants involves [CBSE AIPMT 2015]

(a) infection of the plant by Agrobacterium tumefaciens

(b) altering the $\mathrm{pH}$ of soil, heat-shocking the plants

(c) exposing the plants to cold for a brief period

(d) allowing the plant roots to stand in water

Answer/Explanation

Ans. (a)

Agrobacterium tumefaciens, a pathogen of several dicot plants is able to deliver a piece of DNA known as tDNA to transform normal plant cells into a tumour and direct these tumour cells to produce the chemicals required by the pathogen.

Question

 Which of the following Bt crops is being grown in India by the farmers? [NEET 2013]

(a) Maize

(b) Cotton

(c) Brinjal

(d) Soyabean

Answer/Explanation

Ans. (b)

In India Bt cotton is grown by farmers extensively. Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt). Examples of Bt crops are Bt cotton, Bt corn, rice, tomato, potato and soyabean, etc.

Question

Consumption of which one of the following foods can prevent the kind of blindness associated with vitamin-A deficiency? [CBSE AIPMT 2012]

(a) Flavr savr tomato

(b) Canolla

(c) Golden rice

(d) Bt brinjal

Answer/Explanation

Ans. (c)

Golden rice is a variety of Oryza sativa (rice) produced through genetic engineering to biosynthesise beta-carotene, a precursor of vitamin-A in the edible part of rice (i.e. endosperm). The research that led to golden rice was conducted with the goal of helping children who suffer from vitamin-A deficiency. Because many children in countries where there is a dietary deficiency in vitamin-A rely on rice as a staple food, the genetic modification of rice to produce the vitamin-A precursor beta-carotene is seen as a simple and less expensive alternative to vitamin supplements.

Question

The process of RNA interference has been used in the development of plants resistant to [CBSE AIPMT 2011]

(a) nematodes

(b) fungi

(c) viruses

(d) insects

Answer/Explanation

Ans. (a)

The process of RNA interference (RNAi) has been used in the development of plants resistant to nematodes like Meloidogyne incognitia, which infects the roots of tobacco plants and causes a great reduction in yield. RNA interference takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).

Question

Continuous addition of sugars in ‘fed batch’ fermentation is done to [CBSE AIPMT 2011]

(a) produce methane

(b) obtain antibiotics

(c) purify enzymes

(d) degrade sewage

Answer/Explanation

Ans. (c)

Continuous addition of sugars in fed batch fermentation is done to purify enzymes. A fed batch is a biotechnological batch process which is based on feeding of a growth limiting nutrient substrate to a culture.

Question

 The Genetically Modified (GM) brinjal in India has been developed for [CBSE AIPMT 2010]

(a) insect-resistance

(b) enhancing self life

(c)enhancing mineral content

(d) drought-resistance

Answer/Explanation

Ans. (a)

The genetically modified brinjal or Bt brinjal has the same cry lac gene from Bacillus thuringiensis as cotton. The gene is supposed to make the plant tolerant to the shoot and fruit borer insect, which attacks it throughout its life cycle.

Question

 Some of the characteristics of Bt cotton are [CBSE AIPMT 2010]

(a) long fibre and resistance to aphids

(b) medium yield, long fibre and resistance to beetle pests

(c) high yield and production of toxic protein crystals which kill dipteran pests

(d) high yield and resistance to bollworms

Answer/Explanation

Ans. (c)

Bacillus thuringiensis forms crystals containing a toxic insecticidal protein. Bt toxin protein exists as inactive protein but once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline $\mathrm{pH}$ of the gut, which solubulise the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and eventually cause death of the insect. Specific Bt toxin genes were isolated from B. thuringiensis and incorporated into the several plants such as cotton. The toxin is coded by a gene named cry. There are a number of them, e.g. the proteins encoded by the genes cry I Ac and cry II Ab control the cotton bollworms, that of cry $\mid$ Ab control corn borers.

Question

A transgenic food crop which may help in solving the problem of night blindness in developing countries is [CBSE AIPMT 2008]

(a) Bt soyabean

(b) golden rice

(c) flavr savr tomatoes

(d) starlink maize

Answer/Explanation

Ans. (b)

Vitamin-A deficiency causes night blindness among children. Vitamin-A deficiency often occurs where rice is the staple food since, rice grain does not contain $\beta$-carotene. Three transgenes providing phytoene synthase, phytoene desaturase, beta carotene desaturase and lycopene cyclase activities were transferred into rice by Agrobacterium mediated transformation. The resulting transgenic rice popularly called goldern rice contains good quantities of $\beta$-carotene.
Flavr savr is genetically modified tomato, which remains fresh and retain their flavour much longer than normal tomato due to the blocking of synthesis of fruit softening enzyme polygalacturonase.

Question

Introduction of food plants developed by genetic engineering is not desirable because

(a) economy of developing countries may suffer

(b) these products are less tasty as compared to the already existing products

(c) this method is costly

(d) there is danger of introduction viruses and toxins with introduced crop

Answer/Explanation

Ans. (a)

It is difficult for developing countries to keep up and maintain genetically engineered crops. Therefore, introduction of food plants by genetic engineering is not desirable for developing countries.

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