41. The common nitrogen fixer in paddy fields is [NEET 2010]
(a) Rhizobium (b) Azospirillum
(c) Oscillatoria (d) Frankia
Ans: (b) The common nitrogen fixer in paddy field is Azospirillum. It is an anaerobic bacteria that forms loose association with roots of paddy crops.
42. Which one of the following is not used in organic farming? [NEET 2010]
(a) Glomus (b) Earthworm
(c) Oscillatoria (d) Snail
Ans: (d) Organic farming involves use of organic wastes and other biological material along with beneficial microbes to release nutrients to crop to increase the soil fertility in an ecofriendly, and pollution tree environment. Glomus, earthworm and Oscillatoria can be used in organic farming while snail cannot.
43. Select the correct statement from the following? [NEET 2010]
(a) Biogas is produced by the activity of aerobic bacteria on animal waste
(b) Methanobacterium is an aerobic bacterium found in rumen of cattle
(c) Biogas, commonly called gobar gas, is pure methane
(d) Activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria
Ans: (d) Activated sludge is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans. During the process, the primary effluent is taken to aeration tank that contain large number of aerobic heterotrophic microbes. They form flocs that digest a lot of organic matter. As the biological oxygen demand of waste water is reduced, it is passed into settling tank to undergo sedimentation. The sediment of the settling tank is called activated sludge that is a rich source of aerobic bacteria. Hence, the statement (d) is correct. Biogas is produced by anaerobic breakdown of biomass with the help of methanogenic bacteria. It is made up of methane, carbon dioxide with traces of nitrogen, hydrogen sulphide and hydrogen. Methanobacterium is an anaerobic bacterium that is found in rumen of cattle and is helpful in the breakdown of cellulose.
44. Which one of the following is linked to the discovery of Bordeaux mixture as a popular fungicide? [NEET 2008]
(a) Bacterial leaf blight of rice
(b) Downy mildew of grapes
(c) Loose smut of wheat
(d) Black rust of wheat
Ans: (b) Downy mildew of grapes disesase is linked to the discovery of Bordeux mixture as a popular fungicide. Bordeux mixture was discovered by Millardet in France in 1882. Bordeux mixture is prepared by dissolving 40g of copper sulphate and 40 g of calcium hydroxide in 5 litres of water. Bordeux mixture is used primarily as a fungicide, it was first used to control downy mildew disease of grape-vine caused by a fungus, Plasmopara viticola. The first pesticide to be used commercially was bordeux mixture.
45. For retting of jute the fermenting microbe used is [NEET 2005]
(a) Methophilic bacteria
(b) Butyric acid bacteria
(c) Helicobactor pylori
(d) Streptococcus lactin
Ans: (b) Butyric acid bacteria, Clostridium butylicum causes the retting of fibres. Retting is a stage in the manufacturing of vegetable fibers, especially the bast fibers. It is the process of submerging plant stems such as flax, jute, hemp or kenaf in water, and soaking them for a period of time to loosen the fibers from the other components of the stem. Retting can also be done by letting the cut crop stand in the fields in the wet fall, called “dew retting”. Bacterial action attacks pectin and lignin, freeing the cellulose fibres. The stems are then removed and washed and subjected to mechanical processing to remove the soft tissue and then dried so that all that remains are the fibres.The process is caused by Clostridium butylicum.
46. Which of the following is pair of biofertilizers? [NEET 2001]
(a) Azolla and BGA
(b) Nostoc and legumes
(c) Rhizobium and grasses
(d) Salmonella and E. coli
Ans: (a) Azolla and blue green algae- Anabaena form biofertilizer in rice fields.
47. The aquatic fern, which is an excellent biofertiliser is [NEET 1999]
(a) Azolla (b) Salvinia
(c) Marsilia (d) Pteridium
Ans: (a) Azolla is a freshwater fern harbouring a bluegreen alga – Anabaena in its leaf cavities. The alga fixes atmospheric nitrogen and releases nitrogenous compounds in leaf cavities. This symbiotic system is the main source of algal biofertilizer in rice fields.
48. Due to which of the following organisms, yield of rice has been increased ? [NEET 1999]
(a) Anabaena
(b) Bacillus popilliae
(c) Sesbania
(d) Bacillus polymexa
Ans: (a) Azolla is a freshwater fern harboring a bluegreen alga – Anabaena in its leaf cavities. The alga fixes atmospheric nitrogen and releases nitrogenous compounds in leaf cavities. This symbiotic system is the main source of algal biofertilizer in rice fields. When rice paddies are flooded in the spring, they can be inoculated with Azolla, which then quickly multiplies to cover the water, suppressing weeds. As the plants die, they contribute nitrogen to the rice plants, and as the rice paddy dries out, the Azolla eventually die, making an exceptional green manure.
49. Which one of the following is non-symbiotic biofertilizer? [NEET 1998]
(a) Azotobacter (b) Anabaena
(c) Rhizobium (d) VAM.
Ans: (a) Azotobacter is a free living nitrogen fixing bacterium, Rhizobium is symbiotic and found in the root nodules of leguminous plants, Anabaena occurs in assoction with Azolla. VAM is vesicular arbuscular mycorrhiza.
50. Farmers have reported over 50% higher yields of rice by using the biofertilizer [NEET 1998]
(a) Azolla pinnata
(b) Cyanobacteria
(c) Legume-Rhizobium symbiosis
(d) Mycorrhiza
Ans: (a) Farmers have reported over 50% higher yields of rice by using the biofertilizer Azolla pinnata.
51. Which of the following is likely to be achieved in the coming two decades? [NEET 1997]
(a) A complete understanding of the brainmind interaction
(b) Control of cancer
(c) Correction of genetic basis of diabetes mellitus
(d) Production of biodegradable plastic rather than cellulose by higher plants
Ans: (b) Control of cancer is likely to be achieved in the coming two decades.
52. Gobar gas contains mainly [NEET 1997]
(a) CH4 + CO2 (b) CH4 + O2
(c) CO2 + H2 (d) CO2 + SO2
Ans: (a) Gobar gas contains mainly CH4 + CO2.
53. Azotobacter and Bacillus polymyxa are the examples of [NEET 1996]
(a) symbiotic nitrogen-fixers
(b) non-symbiotic nitrogen-fixers
(c) ammonifying bacteria
(d) disease-causing bacteria
Ans: (b) Azotobacter and Bacillus polymyxa are the examples of non-symbiotic nitrogen-fixers.
54. Non-symbiotic nitrogen fixers are [NEET 1994]
(a) Azotobacter
(b) Pseudomonas
(c) soil fungi
(d) blue-green algae
Ans: (a) Azotobacter are nonsymbiotic, free living nitrogen fixing bacteria. (c) Azotobacter is a free living soil bacterium able to take up dinitrogen from the soil and fix it into organic nitrogenous material like aminoacid. Clostridium is anaerobic free living soil N2 fixing bacteria. Rhizobium is symbiotic N2 fixing bacteria.
55. A nonphotosynthetic aerobic nitrogen fixing soil bacterium is [NEET 1994]
(a) Rhizobium (b) Clostridium
(c) Azotobacter (d) Klebsiella
Ans: (c) Azotobacter is a free living soil bacterium able to take up dinitrogen from the soil and fix it into organic nitrogenous material like aminoacid. Clostridium is anaerobic free living soil N2 fixing bacteria. Rhizobium is symbiotic N2 fixing bacteria. Ω
33. Biotechnology: Principles and Processes
1. The DNA fragments separated on an agarose gel can be visualised after staining with :[NEET 2017]
(a) Acetocarmine
(b) Aniline blue
(c) Ethidium bromide
(d) Bromophenol blue
Ans: (c) Ethidium bromide (Et Br) is used to stain the DNA fragments and will appear as orange coloured bands when kept under UV light.
2. A gene whose expression helps to identify transformed cell is known as : [NEET 2017]
(a) Vector
(b) Plasmid
(c) Structural gene
(d) Selectable marker
Ans: (d) Selectable markers in recombinant DNA technology, helps in identification and elimination of non-transformants and selectively permits the growth of the transformants.
3. What is the criterion for DNA fragments movement on agarose gel during gel electrophoresis? [NEET 2017]
(a) The smaller the fragment size, the farther it moves
(b) Positively charged fragments move to farther end
(c) Negatively charged fragments do not move
(d) The larger the fragment size, the farther it moves
Ans: (a) DNA fragments during gel electrophoresis, separate (resolve) according to their size due to sieving effect provided by agarose gel.
4. Which of the following is not a feature of the plasmids? [NEET 2016]
(a) Independent replication
(b) Circular structure
(c) Transferable
(d) Single – stranded
Ans: (d) Plasmid has an extra chromosomal, double stranded circular DNA.
5. The taq polymerase enzyme is obtained from
(a) Thermus aquaticus [NEET 2016]
(b) Thiobacillus ferroxidans
(c) Bacillus subtilis
(d) Pseudomonas putida
Ans: (a) The Taq polymerase enzyme is obtained from Thermus aquaticus which lives in hot springs.
6. Which of the following is a restriction endonuclease? [NEET 2016]
(a) Hind II (b) Protease
(c) DNase I (d) RNase
Ans: (a) A restriction enzyme or restriction endonuclease is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Hind II among these is a type of restriction endonuclease.
7. The cutting of DNA at specific locations became possible with the discovery of
(a) Probes [NEET 2015 RS]
(b) Selectable markers
(c) Ligases
(d) Restriction enzymes
Ans: (d) Restriction enzymes are used to cut DNA at specific locations.
8. The DNA molecule to which the gene of interest is integrated for cloning is called: [NEET 2015 RS]
(a) Vector (b) Template
(c) Carrier (d) Transformer
Ans: (a) A vector is a DNA molecule which is used as a vehicle to carry the gene of interest to another cell.
9. An analysis of chromosomal DNA using the Southern hybridization technique does not use: [NEET 2014]
(a) Electrophoresis (b) Blotting
(c) Autoradiography (d) PCR
Ans: (d) PCR is a technique for enzymatically replicating DNA without using a living organism such as E. coli or Yeast. It is commonly used in medical and biological research labs for a variety of tasks like detection of hereditary diseases, identification of genetic fingerprints etc.
10. Which vector can clone only a small fragment of DNA? [NEET 2014]
(a) Bacterial artificial chromosome
(b) Yeast artificial chromosome
(c) Plasmid
(d) Cosmid
Ans: (c) Plasmids are small extranuclear circular DNAs which carry extrachromosomal genes in bacteria and some fungi. They replicate independently. The best known vectors which are also available commerciallly are pBR322 and pUC-18.
11. During the process of isolation of DNA, chilled ethanol is added to [NEET NEET Kar. 2013]
(a) Remove proteins such as histones
(b) Precipitate DNA
(c) Break open the cell to release DNA
(d) Facilitate action of restriction enzymes
Ans: (b) Ethanol is non-polar molecule while DNA is a polar molecule, it has a net negative charge due to the phosphate groups attached to it. When DNA is placed into a solution of 100% ethanol, it becomes insoluble and precipitates out of solution.
12. The colonies of recombinant bacteria appear white in contrast to blue colonies of nonrecombinant bateria because of : [NEET NEET 2013]
(a) Insertional inactivate of alphagalactosidase in non-recombinant bacteria
(b) Insertional inactivation of alphagalactosidase in recombinant bacteria
(c) Inactivation of glycosidase enzyme in recombinant bacteria
(d) Non-recombinant bacteria containing beta-galactosidase
Ans: (d) Alternative selectable markers have been developed which differentiate recombinant from non-recombinants on the basis of their ability to produce colour in the presence of chromogenic substrate. In this , a recombinant DNA is inserted within the coding sequence of an enzyme -galactosidase. This results into inactivation of the enzyme, which is referred to as insertional inactivation. The presence of chromogenic substrate give blue coloured colonies of the plasmid in the bacteria does not have an insert. Presence of insert results into insertional inactivation of the galactosidase and the colonies do not produce any colour, these are identified as recombinant colonies.
13. Genes of interest can be selected from a genomic library by using [NEET NEET Kar. 2013]
(a) Restriction enzymes
(b) Cloning vectors
(c) DNA probes
(d) Gene targets
Ans: (c) A hybridization probe is a fragment of DNA of variable length which is used in DNA samples to detect the presence of nucleotide sequence (the DNA target) that are complementary to the sequence in the probe. The probe hybridize to single–stranded DNA whose base sequence allow probe target base-pairing due to complementary between the probe and target.
14. The figure below is the diagrammatic representation of the E.Coli vector pBR 322. Which one of the given options correctly identifies its certain component (s) ? [NEET 2012] EcoR I Cla Hind III Pvu I Pvu II BamH 1 Sal I Pst I amp2 tet2 pBR322 ori rop
(a) ori – original restriction enzyme
(b) rop-reduced osmotic pressure
(c) Hind III, EcoRI – selectable markers
(d) ampR, tetR – antibiotic resistance genes
Ans: (d) In pBR 322 ori-represents site of origin or replication rop-represents those proteins that take part in replication of plasmid. Hind III, EcoRI- Recoginition sites of Restriction endonucleases ampR and tetR – They are antibiotic resistant gene part
15. A single strand of nucleic acid tagged with a radioactive molecule is called : [NEET 2012]
(a) Vector (b) Selectablemarker
(c) Plasmid (d) Probe
Ans: (d) A single strand DNA or RNA tagged with radioactive molecule that is used in hybridization of DNA or RNA is called probe.
16. Which one of the following represents a palindromic sequence in DNA? [NEET 2012M]
(a) 5′ – GAATTC – 3′ 3′ – CTTAAG – 5′
(b) 5′ – CCAATG – 3′ 3′ – GAATCC – 5′
(c) 5′ – CATTAG – 3′ 3′ – GATAAC – 5′
(d) 5′ – GATACC – 3′ 3′ – CCTAAG – 5′
Ans: (a) A palindromic sequence is a nucleic acid sequence (DNA or RNA) that is the same whether read 5′ (five-prime) to 3′ (three prime) on one strand or 5′ to 3′ on the complementary strand with which it forms a double helix. 5′ – GAATTC – 3′ 3′ – CTTAAG – 5′ It is a palindromic sequence of DNA cut by restriction enzyme Eco RI.
17. Which one of the following techniques made it possible to genetically engineer living organism ? [NEET 2011M]
(a) Recombinant DNA techniques
(b) X-ray diffraction
(c) Heavier isotope labelling
(d) Hybridization
Ans: (a) Recombinant DNA technology is the process joining together two DNA molecules from two different species that are inserted into a host organism to produce new genetic combination.
18. There is a restriction endonuclease called EcoRI. What does “co” part in it stand for ?
(a) colon (b) coelom [NEET 2011]
(c) coenzyme (d) coli
Ans: (d) EcoRI is an endonuclease enzyme isolated from strains of E.coli and a part of restriction modified system. So co part stands for coli.
19. Which one of the following is used as vector for cloning genes into higher organisms?
(a) Baculovirus [NEET 2010]
(b) Salmonella typhimurium
(c) Rhizopus nigricans
(d) Retrovirus
Ans: (d) Retrovirus as has the ability to transform normal cells into cancerous cells. Hence, it can used as a vector for cloning desirable genes into animal cells.
20. Which one of the following palindromic base sequences in DNA can be easily cut at about the middle by some particular restriction enzyme? [NEET 2010]
(a) 5’………….CGTTCG………….3′ 3’………….ATGGTA………….5′
(b) 5’………….GATATG………….3′ 3’………….CTACTA………….5′
(c) 5’………….GAATTC………….3′ 3’………….CTTAAG………….5′
(d) 5’………….CACGTA………….3′ 3’………….CTCAGT………….5′
Ans: (c) Palindromic sequences in DNA molecule are group of bases that forms the same sequence when read in both forward and backward direction. In the given question, only option (c) represent a palindromic sequence.