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Given below are two statements:
Statement I : Bt toxins are insect group specific and coded by a gene cry IAc.
Statement II : Bt toxin exists as inactive protoxin in B. thuringiensis. However, after ingestion by the insect the inactive protoxin gets converted into active form due to acidic \(\mathrm{pH}\) of the insect gut.
In the light of the above statements, choose the correct answer from the options given below: [NEET 2024]
Answer (3)
The correct answer is option (3) as specific \(\mathrm{Bt}\) toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The choice of genes depends upon the crop and the targeted pest as most \(B\) t toxins are insect-group specific. The toxin is coded by a gene named \(c r y\). There are a number of them, for example, the proteins encoded by the genes cry IAc and cry \|Ab control the cotton bollworms, that of cry IAb controls corn borer.
Which of the following statements is incorrect? [NEET 2024]
Answer (3)
Sol. Correct answer is option (3)
The statement (3) is incorrect because bioreactors are used for processing of large volumes (100 1000 litres) of culture.
Small volume cultures cannot yield appreciable quantities of products. To produce in large quantities the development of bioreactors is required.
Which one of the following techniques does not serve the purpose of early diagnosis of a disease for its early treatment? [NEET 2023]
Answer (2)
Sol. The correct answer is option (2) because using conventional methods of diagnosis like serum and urine analysis, etc, do not help in early diagnosis. Recombinant DNA technology, Polymerase Chain Reaction [PCR] and Enzyme Linked Immuno-Sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.
Which of the following is not a cloning vector? [NEET 2023]
Answer (4)
Sol. Option (4) is correct answer because a single stranded DNA or RNA tagged with a radioactive molecule is called a probe and it helps in the detection of mutated gene.
Option (2), (3) and (1) are not correct because YAC, BAC, pBR322 are vectors.
Given below are two statements : one is labelled as
Assertion (A) and the other is labelled as Reason (R).
Assertion \(\)(A)\(\) :
Polymerase chain reaction is used in DNA amplification.
Reason (R) :
The ampicillin resistant gene is used as a selectable marker to check transformation
In the light of the above statements, choose the correct answer from the options given below : [NEET 2022]
Answer (2)
Sol. Option (2) is the correct answer because both the statements are correct but the given reason is not the correct explanation. Polymerase chain reaction is used in DNA amplification.
Ampicillin resistance gene is a selectable marker that helps to check transformation by selection of transformants.
Which kind of therapy was given in 1990 to a four-year-old girl with adenosine deaminase (ADA) deficiency?
(NEET-II 2016)
(a): Gene therapy is a technique of genetic engineering which involves replacement of a faulty/ disease causing gene by a normal healthy functional gene. The first clinical gene therapy was given in 1990 to a 4 -year old girl with adenosine deaminase (ADA) deficiency. This enzyme is very important for the immune system to function. The deficiency of this enzyme can lead to severe combined immune deficiency (SCID).
The two polypeptides of human insulin are linked together by (NEET-I 2016)
(b) : Human insulin is made up of 51 amino acids arranged in two polypeptide chains. Chain A has 21 amino acids and chain \(\mathrm{B}\) has 30 amino acids. The two polypeptide chains are interconnected by disulphide bridges or S-S-linkages.
Which part of the tobacco plant is infected by Meloidogyne incognita? (NEET-I 2016)
(b) : Meloidogyne incognita is a nematode which infects the roots of the tobacco plants and causes a great reduction in the yield.
Golden rice is a genetically modified crop plant where the incorporated gene is meant for biosynthesis of
(NEET 2015)
(b) : Golden rice is a transgenic variety of rice (Oryza sativa) which contains good quantities of \(\beta\)-carotene (provitamin A – inactive state of vitamin
A). \(\beta\)-carotene is a principal source of vitamin A. Since the grains of this rice is yellow in colour due to \(\beta\)-carotene and commonly called golden rice.
The introduction of T-DNA into plants involves (NEET 2015)
(c) : Ti plasmid (tumor inducing) from the soil bacterium Agrobacterium tumefaciens is effectively used as vector for gene transfer to plant cells. The part of Ti plasmid transferred into plant cell DNA, is called the T-DNA. This T-DNA with desired DNA spliced into it, is inserted into the chromosomes of the host plant where it produces copies of itself, by migrating from one chromosomal position to another at random. Such plant cells are then cultured, induced to multiply and differentiate to form plantlets. Transferred into soil, the plantlets grow into mature plants, carrying the foreign gene, expressed throughout the new plant.
In \(\mathrm{Bt}\) cotton, the \(\mathrm{Bt}\) toxin present in plant tissue as protoxin is converted into active toxin due to
(2015 Cancelled)
(c) : Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms some protein crystals. These crystals contain a toxic insecticidal protein. This toxin does not kill the Bacillus (bacterium) because it exists as inactive protoxins in them. But, once an insect ingests it, it is converted into an active form of toxin due to the alkaline \(\mathrm{pH}\) of the alimentary canal. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause swelling and lysis and finally cause death of the insect.
Which body of the Government of India regulates GM research and safety of introducing GM organisms for public services?
(2015 Cancelled)
(a) : Genetic modification of organisms can have unpredictable results, when such organisms are introduced into the ecosystem. Therefore, the Indian Government has set up organizations such as GEAC (Genetic Engineering Approval Committee), which makes decisions regarding the validity of GM research and the safety of introducing GM-organisms for public services.
The crops engineered for glyphosate are resistant/tolerant to (2015 Cancelled)
(b) : Glyphosate is a broad spectrum herbicide which especially kills broad leaved herbs. Crop plants may also get affected by the herbicide, thus now crop plants are genetically engineered for glyphosate resistance. So, when glyphosate herbicide is applied, only weeds and no crop plants get harmed.
The first human hormone produced by recombinant DNA technology is (NEET 2014)
(a): The recombinant DNA technological processes have made great impact in the area of health care by mass production of safe and more effective therapeutic drugs. In 1983, Eli Lily, an American company, first prepared two DNA sequences corresponding to \(\mathrm{A}\) and \(\mathrm{B}\) chains of human insulin and introduced them in plasmids of Escherichia coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin (humulin).
Which of the following \(\mathrm{Bt}\) crops is being grown in India by the farmers? (NEET 2013)
(d) : Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The choice of genes depends upon the crop and targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene named cry. These are numerous genes. Two cry genes cry I Ac and cry II Ab have been incorporated in cotton. The genetically modified crop is called \(\mathrm{Bt}\) cotton as it contains \(\mathrm{Bt}\) toxin genes against cotton bollworms.
RNA interference involves (Karnataka NEET 2013)
(b): RNA interference (RNAi) is the phenomenon of inhibiting activity of a gene through production of both sense and antisense RNA. RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves a specific \(m\) RNA silencing. It is due to a complementary dsRNA molecule which binds to and prevents translation of the \(m\) RNA causing its silencing.
Which one of the following vectors is used to replace the defective gene in gene therapy? (Karnataka NEET 2013)
(a) : Gene therapy is a corrective therapy that is given to patients of diseases caused by some gene defects. Here, genes are inserted into a person’s cells and tissues to treat disease by replacing the defective gene. The normal gene delivered into the individual or embryo takes over the function and compensate for the normal gene. Viral vectors like adenovirus are generally used to deliver the normal gene.
Consumption of which one of the following foods can prevent the kind of blindness associated with vitamin ‘A’ deficiency?
(Mains 2012)
(c):
Tobacco plants resistant to a nematode have been developed by the introduction of DNA that produces (in the host cells)
(Mains 2012)
(a): Many nematodes live in plants and animals including human beings. A nematode Meloidogyne incognita infests the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infection that was based on the process of RNA interference (RNAi). RNA interference (RNAi) is the phenomenon of inhibiting activity of a gene by synthesis of RNA molecules complementary to the \(m\) RNA. The normal (in vivo synthesized) \(m\) RNA of a gene is said to be “sense” because it carries the codons that are “read” during translation. Normally, the complement to the \(m\) RNA “sense” strand will not contain a sequence of codons that can be translated to produce a functional protein; thus, this complementary strand is called “anti-sense RNA”. The anti-sense RNA and \(m\) RNA molecules will anneal to form duplex RNA molecules (or double stranded RNA) and the duplex RNA molecules can not be translated. Thus, the presence of anti-sense RNA will block translation of the \(m\) RNA of the affected gene. In fact, recent evidence indicates that these RNA duplexes are often rapidly degraded in vivo.
What is it that forms the basis of DNA fingerprinting? (Mains 2012)
(d): DNA fingerprinting is a technique of determining nucleotide sequences of certain areas of DNA which are unique to each individual. The difference of about \(0.1 \%\) or \(3 \times 10^6\) base pairs (out of \(3 \times 10^9 \mathrm{bp}\) ) provides individuality to each human being. Human genome possesses numerous small noncoding but inheritable sequences of bases which are repeated many times. These sequences occur near telomere, centromeres, Y chromosome and heterochromatic area. The area with same sequence of bases repeated several times is called repetitive DNA. It is separated as satellite from the bulk DNA during density gradient centrifugation and hence called satellite DNA where, repetition of bases is in tandem. Satellite DNAs show polymorphism (the occurrence of mutations in a population at high frequency), which is the basis of genetic mapping of human genome as well as DNA fingerprinting. While mutations in genes produce alleles with different expressions, mutations in noncoding repetitive DNA have no immediate impact. These mutations which have piled up with time form the basis of polymorphism.
The first clinical gene therapy was given for treating (Mains 2012)
(d): Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. Here genes are inserted into a person’s cells and tissues to treat a disease. Correction of a genetic defect involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene. The first clinical gene therapy was given in 1990 to a 4 – year old girl with adenosine deaminase (ADA) deficiency. This enzyme is very important for the immune system to function. SCID is caused due to defect in the gene for the enzyme adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation. Here, the isolated gene from bone marrow cells producing ADA is introduced into cells at early embryonic stages; it can be a permanent cure.
Maximum number of existing transgenic animals is of (NEET 2011)
(b)
The process of RNA interference (RNAi) has been used in the development of plants resistant to (NEET 2011)
(a):
Bacillus thuringiensis forms protein crystals which contain insectidical protein. This protein (NEET 2011)
(a):
Silencing of \(m\) RNA has been used in producing transgenic plants resistant to (NEET 2011)
(b)
Read the following four statements (A-D) about certain mistakes in two of them.
(A) The first transgenic buffalo, Rosie produced milk which was human alphalactalbumin enriched.
(B) Restriction enzymes are used in isolation of DNA from other macromolecules.
(C) Downstream processing is one of the steps of rDNA technology.
(D) Disarmed pathogen vectors are also used in transfer of rDNA into the host.
Which of the two statements have mistakes? (Mains 2011)
(d): In 1997, the first transgenic cow, Rosie, produced human protein enriched milk. The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk. Isolation of DNA from other macromolecule is achieved by treating the bacterial cells/plant or animal tissue with enzymes such as lysozyme (bacteria), cellulase (plant cells), chitinase (fungus).
The genetically-modified (GM) brinjal in India has been developed for (NEET 2010)
(a) : The genetically modified (GM) Bt brinjal in India has been developed mainly for insect resistance. Through genetic engineering Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton, brinjal.
Genetic engineering has been successfully used for producing (NEET 2010)
(a) : Many transgenic animals are designed to increase our understanding of how genes contribute to the development of diseases. These are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s. Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine.
Some of the characteristics of Bt cotton are (NEET 2010)
(d) : Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into cotton plant. The genetically modified crop is called \(\mathrm{Bt}\) cotton. Bt cotton has the following useful characteristics: pest resistance, herbicide tolerance, high yield and resistance to bollworm infestation.
An improved variety of transgenic basmati rice (NEET 2010)
(b)
Which one of the following is now being commercially produced by biotechnological procedures? (Mains 2010)
(d) : Insulin is now being commercially produced by genetic engineering. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bonds. Insulin, in mammal is synthesised as a prohormone which contains an extra stretch called the C-peptide. During maturation this C-peptide is removed. The production of insulin could only have been commercially possible if somehow the maturation process of \(\mathrm{C}\)-peptide been skipped.
This problem was solved in 1988 by Eli Lilly, an American company which prepared functionable insulin from two DNA sequences corresponding to \(\mathrm{A}\) and \(\mathrm{B}\) chains of human insulin and introduced them in plasmids of E.coli to produce insulin chains. In this way, chains A and B were produced separately which was extracted, combined by creating disulfide bonds to get human insulin.
What is true about \(\mathrm{Bt}\) toxin? (NEET 2009)
(d) : Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms some protein crystals. These crystals contain a toxic insecticidal protein. This toxin does not kill the Bacillus (bacterium) because it exists as inactive protoxins in them. But, once an insect ingests it, it is converted into an active form of toxin due to the alkaline \(\mathrm{pH}\) of the alimentary canal. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause swelling and lysis and finally cause death of the insect.Â
Transgenic plants are the ones (NEET 2009)
(a) : The plants produced through genetic engineering contain gene or genes usually from an unrelated organism. Such genes are called transgenes and the plants having transgenes are called transgenic plants. Recombinant DNA techniques are being used to improve crop plants by increasing their productivity, by making them more nutritious, and by developing disease resistance. Transgenic plants have a natural resistance to herbicides and pests. In the future, plants may have an ability to fix atmospheric nitrogen and an increased ability to grow in arid and salty soils.
The bacterium Bacillus thuringiensis is widely used in contemporary biology as (NEET 2009)
(a): Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms some protein crystals. These crystals contain a toxic insecticidal protein. This toxin does not kill the Bacillus (bacterium) because it exists as inactive protoxins in them. But, once an insect ingests it, it is converted into an active form of toxin due to the alkaline \(\mathrm{pH}\) of the alimentary canal. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause swelling and lysis and finally cause death of the insect.Â
What is antisense technology? (NEET 2009)
(a):
Cry I endotoxins obtained from Bacillus thuringiensis are effective against (NEET 2008)
(b)
A transgenic food crop which may help in solving the problem of night blindness in developing countries is
(NEET 2008)
(b)
Main objective of production/use of herbicide resistant GM crops is to (NEET 2008)
(c): Genetic engineering has helped to develop such transgenic crop plants which are resistant to herbicides so that they are not damaged when farmers spray herbicides in the fields. Herbicide resistant plants have been developed in such a way that they continue to produce normal crop yield and at the same time remain unaffected by the activity of herbicides. These plants also reduces the use of weeding labour, farmer’s cost and increases yield.
Human insulin is being commercially produced from a transgenic species of (NEET 2008)
(c):
A genetically engineered micro-organism used successfully in bioremediation of oil spills is a species of
(NEET 2007)
(d) : Bioremediation is the process of using living micro-organisms to clean up a contaminated site. Micro-organisms do this by removing toxins from materials. They decompose these compounds by using enzymes, specific proteins that control reactions in living cells. Organisms that produce enzymes capable of degrading petroleum are useful in cleaning up oil spills. Some common ones that break down oil are genetically engineered species of Pseudomonas and Azotobacter. Bioremediation accounts for 5 to 10 percent of all pollution treatment and has been used successfully in cleaning up leaking underground gasoline storage tanks. Bioremediation has many applications, from the ordinary garden compost to the removal of selenium and other toxic metals from waste. The best agents for bioremediation are the ones that can break down contaminants without becoming contaminated or harmful themselves.
Golden rice is a promising transgenic crop. When released for cultivation, it will help in (NEET 2006)
(b):
Bacillus thuringiensis (Bt) strains have been used for designing novel (NEET 2005)
(d) : Bacillus thuringiensis strains have been used for designing bioinsecticidal plants. A gene from this bacteria have insecticidal property which is transferred to cotton plants to produce \(\mathrm{Bt}\) cotton which is resistant to bollworm insect which is a major pest of cotton. Similarly insects affecting maize; cabbage, sunflower etc., are also controlled by mutant strains of Bacillus thuringiensis bacteria.
Production of a human protein in bacteria by genetic engineering is possible because (NEET 2005)
(d) : Genetic code may be defined as the sequence of nucleotides in polynucleotide chain which determines the sequence of amino acids in a polypeptide chain. Thus the genetic code is universal. These is no ambiguity regarding genetic code. It means that each codon codes for the same amino acid in all organisms including bacteria, plants and animals.
Golden rice is a transgenic crop of the future with the following improved trait (NEET 2005)
(d) : Golden rice is a transgenic crop rice with high vitamin A content. It has been developed by transferring beta carotene synthesizing gene into the transgenic rice. Beta carotene is the precursor of vitamin A. This transgenic rice has been crossed with the already adapted varieties of rice to make them grow well in a particular area. It is very useful for the people suffering from vision impairment due to vitamin A deficiency.
DNA fingerprinting refer to (NEET 2004)
(a):
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