Biotechnological Applications in Agriculture Questions in English

(A) transgenic food crop which may help in solving the problem of night blindness in developing countries is golden rice.
Golden rice is a genetically modified rice variety that has been engineered to produce elevated levels of beta-carotene.
Beta-carotene is a precursor of vitamin $A$,which helps in preventing night blindness.
This modification gives the rice its characteristic golden colour.

(C) Basmati rice was patented by a $U.S.$ company in $1997$ through the $U.S.$ Patent and Trademark Office. This was controversial because India has been cultivating diverse varieties of Basmati rice for centuries,and it is a traditional crop of the Indian subcontinent.

(A) $Bt-$ cotton is a transgenic crop. Transgenic plants are those plants which have a foreign gene incorporated into their $DNA$. This insect-resistant gene is derived from a bacterium, $Bacillus$ $thuringiensis$. The insertion of this specific gene allows the cotton plant to produce an insecticidal protein, making it resistant to pests. Therefore, the Reason correctly explains why the $Bt$ gene is used to produce insect-resistant cotton.

(A) $RNAi$ ($RNA$ interference) is a method of cellular defense in all eukaryotic organisms.
In this process,a specific messenger $RNA$ $(mRNA)$ is prevented from translation due to the presence of a complementary double-stranded $RNA$ $(ds-RNA)$ molecule.
The $ds-RNA$ binds to and silences the specific $mRNA$,thereby preventing the synthesis of the corresponding protein.
Therefore,the correct answer is $ds-RNA$.

(N/A) $Bt$ cotton is a well-known example of a genetically modified crop. It has been engineered by introducing the $cry$ genes from the bacterium $Bacillus$ $thuringiensis$ into the cotton plant,which allows the plant to produce an insecticidal protein that protects it from pests like bollworms.

(A) The correct answer is $A$.
In bacteria,the $Bt$ toxin is produced in an inactive form known as a protoxin.
This inactive form does not harm the bacterial cell because it requires an alkaline $pH$ (found in the gut of specific insects) to be converted into its active,toxic form.
Once ingested by the insect,the alkaline environment solubilizes the crystals and activates the toxin,which then binds to the midgut epithelial cells,causing cell lysis and death of the insect.

(N/A) The production of genetically modified $(GM)$ or transgenic plants has several advantages.
Most of the $GM$ crops have been developed for pest resistance,which increases crop productivity and therefore reduces the reliance on chemical pesticides.
Many varieties of $GM$ food crops have been developed with enhanced nutritional quality. For example,golden rice is a transgenic variety of rice which is rich in vitamin $A$.
These plants prevent the loss of soil fertility by increasing the efficiency of mineral usage.
They are highly tolerant to unfavourable abiotic conditions.
The use of $GM$ crops decreases post-harvesting loss of crops.
However,there are certain controversies regarding the use of genetically modified crops around the world. The use of these crops can affect the native biodiversity in an area. For example,the use of $Bt$ toxin to decrease the amount of pesticide poses a threat to beneficial insect pollinators such as honey bees. If the gene expressed for $Bt$ toxin is expressed in the pollen,then the honey bee might be affected. As a result,the process of pollination by honey bees would be affected. Also,genetically modified crops may affect human health by introducing allergens and certain antibiotic resistance markers into the body. Furthermore,they can cause genetic pollution in the wild relatives of the crop plants,thereby affecting our natural environment.

(N/A) Cry proteins are toxic proteins encoded by $cry$ genes. These are produced by the bacterium $Bacillus$ $thuringiensis$ $(Bt)$.
In the bacterium,these proteins exist in an inactive protoxin form.
When an insect ingests these proteins,the alkaline $pH$ of the insect's gut solubilizes the crystals and activates the toxin.
The activated toxin binds to the surface of midgut epithelial cells and creates pores,causing cell swelling and lysis,which leads to the death of the insect.
Humans have exploited this mechanism to develop insect-resistant transgenic crops,such as $Bt$ cotton and $Bt$ corn,by incorporating $cry$ genes into the plant genome.

(N/A) Recombinant $DNA$ technology $(rDNA)$ is a technique used for manipulating the genetic material of an organism to obtain desired traits.
Oil is primarily composed of triglycerides,which are esters of glycerol and fatty acids.
By using $rDNA$ technology,scientists can identify and silence or remove the specific genes responsible for the biosynthesis of either glycerol or fatty acids within the seed.
If the metabolic pathway for oil synthesis is interrupted at the genetic level,the plant will produce seeds that are devoid of oil or have significantly reduced oil content.

(N/A) Golden rice is a genetically modified variety of rice, $Oryza \text{ } sativa$, which has been developed as a fortified food for areas where there is a shortage of dietary vitamin $A$.
It contains a precursor of pro-vitamin $A$, called beta-carotene, which has been introduced into the rice through genetic engineering.
The rice plant naturally produces beta-carotene pigment in its leaves.
However, it is absent in the endosperm of the seed because beta-carotene pigment helps in the process of photosynthesis, while photosynthesis does not occur in the endosperm.
Since beta-carotene is a precursor of pro-vitamin $A$, it is introduced into the rice variety to fulfill the shortage of dietary vitamin $A$.
It is a simple and less expensive alternative to vitamin supplements.
However, this variety of rice has faced significant opposition from environmental activists and is still not widely available in the market for human consumption.

(N/A) There are three options for increasing food production: $(i)$ Agrochemical-based agriculture,$(ii)$ Organic agriculture,and $(iii)$ Genetically engineered crop-based agriculture.
The Green Revolution succeeded in tripling the food supply,but it was not enough to feed the growing human population.
Increased yields have partly been due to the use of improved crop varieties,but mainly due to the use of better management practices and agrochemicals (pesticides and fertilizers).
However,for farmers in the developing world,agrochemicals are often too expensive. Genetically modified $(GM)$ crops are useful to obtain better yields.
Plants,bacteria,fungi,and animals whose genes have been altered by manipulation are called Genetically Modified Organisms $(GMOs)$.
$GM$ plants have been useful in many ways:
$(i)$ Made crops more tolerant to abiotic stresses (cold,drought,salt,heat).
$(ii)$ Reduced reliance on chemical pesticides (pest-resistant crops).
$(iii)$ Helped to reduce post-harvest losses.
$(iv)$ Increased efficiency of mineral usage by plants (this prevents early exhaustion of soil fertility).
$(v)$ Enhanced nutritional value of food,e.g.,Golden Rice,which is Vitamin $A$-enriched rice.
In addition,$GM$ technology has been used to create tailor-made plants to supply alternative resources to industries,such as starches,fuels,and pharmaceuticals.
$Bt$ toxin is produced by a bacterium called $Bacillus$ $thuringiensis$. The $Bt$ toxin gene has been cloned from the bacteria and expressed in plants to provide resistance to insects,effectively creating a bio-pesticide. Examples include $Bt$ cotton,rice,tomato,potato,and soybean.

(N/A) Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm,armyworm),coleopterans (beetles) and dipterans (flies,mosquitoes).
$B$. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein.
The $Bt$ toxin protein exists as an inactive protoxin,but once an insect ingests the inactive toxin,it is converted into an active form of toxin due to the alkaline $pH$ of the gut,which solubilizes the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis,eventually causing the death of the insect.
Specific $Bt$ toxin genes were isolated from Bacillus thuringiensis and incorporated into several crop plants,such as cotton.
The choice of genes depends upon the crop and the targeted pest,as most $Bt$ toxins are insect-group specific.
The toxin is coded by a gene named $cry$. There are a number of them.
For example,the proteins encoded by the genes $cryIAc$ and $cryIIAb$ control the cotton bollworms,and $cryIAc$ controls the corn borer.

(N/A) Pest-resistant plants are developed to reduce the reliance on chemical pesticides. $A$ notable example is the protection of tobacco plants against the nematode $Meloidogyne$ $incognita$,which infects roots and reduces yield.
$RNA$ interference $(RNAi)$ is a method of cellular defense that occurs in all eukaryotic organisms. It involves the silencing of a specific $mRNA$ due to a complementary $dsRNA$ molecule that binds to and prevents the translation of the $mRNA$.
Mechanism of $RNAi$:
$1$. Using $Agrobacterium$ vectors,nematode-specific genes are introduced into the host plant.
$2$. The introduced $DNA$ is designed to produce both sense and antisense $RNA$ in the host cells.
$3$. These two $RNA$ strands are complementary to each other and form a double-stranded $RNA$ $(dsRNA)$.
$4$. This $dsRNA$ initiates the $RNAi$ process,which silences the specific $mRNA$ of the nematode.
$5$. Consequently,the parasite cannot survive in the transgenic host,and the plant is protected from the infestation.

(N/A) $Bt$ protein does not kill $Bacillus$ because the $Bt$ toxin protein exists as an inactive protoxin within the bacterium. It only becomes active when ingested by an insect. The alkaline $pH$ of the insect's gut solubilizes the crystals,converting the inactive protoxin into an active toxin. Since $Bacillus$ lacks this specific alkaline environment and the necessary physiological conditions,the toxin remains inactive and harmless to the bacterium itself.

(N/A) $GMO$ stands for Genetically Modified Organism. It differs from a hybrid because in a hybrid,a cross is performed between different genomes of two species or strains through traditional breeding methods. In contrast,in a $GMO$,specific foreign gene$(s)$ are introduced into the organism's genome using recombinant $DNA$ technology,and these genes are either maintained as extra-chromosomal entities or integrated into the host genome to express desired traits.

(B) $GEAC$ stands for Genetic Engineering Appraisal Committee. It is an Indian government organization established under the Ministry of Environment,Forest and Climate Change.
Its primary objectives are:
$(a)$ To examine the validity of research involving $GM$ (Genetically Modified) organisms.
$(b)$ To inspect the safety of introducing $GM$ organisms for public services and environmental release.

(A) The Indian $Basmati$ rice was crossed with semi-dwarf varieties to create a new variety. $A$ $USA$ company filed for a patent on this new variety,claiming it as their own invention,which led to significant controversy regarding biopiracy.

(N/A) $(i)$ Made crops more tolerant to abiotic stresses (cold,drought,salt,heat).
$(ii)$ Reduced reliance on chemical pesticides (pest-resistant crops).
$(iii)$ Helped to reduce post-harvest losses.
$(iv)$ Increased efficiency of mineral usage by plants (this prevents early exhaustion of soil fertility).
$(v)$ Enhanced nutritional value of food,e.g.,Vitamin $A$ enriched rice.

(A) Several nematodes parasitize a wide variety of plants and animals,including human beings. $A$ nematode $Meloidogyne \text{ } incognitia$ infects the roots of tobacco plants and causes a great reduction in yield.
$A$ novel strategy was adopted to prevent this infestation,which was based on the process of $RNA$ interference $(RNAi)$.
$RNAi$ 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).
The source of this complementary $RNA$ could be from an infection by viruses having $RNA$ genomes or mobile genetic elements (transposons) that replicate via an $RNA$ intermediate.
Using $Agrobacterium$ vectors,nematode-specific genes were introduced into the host plant. The introduction of $DNA$ was such that it produced both sense and anti-sense $RNA$ in the host cells.
These two $RNA$ molecules,being complementary to each other,formed a double-stranded $RNA$ $(dsRNA)$ that initiated $RNAi$ and thus,silenced the specific $mRNA$ of the nematode. The consequence was that the parasite could not survive in a transgenic host expressing specific interfering $RNA$. The transgenic plant,therefore,became protected from the parasite.

(N/A) $(i)$ Made crops more tolerant to abiotic stresses (cold,drought,salt,heat).
$(ii)$ Reduced reliance on chemical pesticides (pest-resistant crops).
$(iii)$ Helped to reduce post-harvest losses.
$(iv)$ Increased efficiency of mineral usage by plants (this prevents early exhaustion of soil fertility).
$(v)$ Enhanced nutritional value of food,e.g.,Vitamin $A$ enriched rice.

(N/A) Biofortified crops include varieties of maize,wheat,rice,bathua,spinach,and pulses. For example,maize hybrids have twice the amount of amino acids (lysine and tryptophan),fortified wheat varieties have high protein content,and fortified rice has a high quantity of iron. Consumption of such biofortified foods enriches the nutritive value of common diets and significantly improves public health. By incorporating $2$ or $3$ essential nutrients into a single crop,we can overcome several nutrient deficiency disorders common in our country without needing to consume a wide variety of different food items.

(A) $Bacillus \text{ } thuringiensis$ (Bt) produces a specific insecticidal protein known as the cry protein or endotoxin.
When the caterpillars of insect pests ingest these bacterial spores or crystals, the alkaline $pH$ of the insect gut solubilizes the crystals and releases the active toxin.
This active toxin binds to the surface of the midgut epithelial cells and creates pores, causing cell swelling and lysis.
This process eventually leads to the death of the insect larvae, thereby controlling the pest population.

(B) $Bt$ cotton is genetically modified to express insecticidal proteins derived from the bacterium $Bacillus$ $thuringiensis$.
These proteins are specifically toxic to certain orders of insects,primarily lepidopterans (e.g.,tobacco budworm,armyworm),coleopterans (e.g.,beetles),and dipterans (e.g.,flies,mosquitoes).
$Bt$ cotton is not a universal pesticide; it does not provide resistance against all types of pests,such as sucking pests,fungal pathogens,or viral diseases.
Therefore,it is only resistant to the specific groups of insects for which the $Cry$ proteins are effective.

(N/A) The applications of biotechnology include:
$(i)$ Therapeutics and diagnostics.
$(ii)$ Genetically modified crops for agriculture.
$(iii)$ Processed food production.
$(iv)$ Bioremediation of environmental pollutants.
$(v)$ Waste treatment and energy production.

(D) Plants,bacteria,fungi,and animals whose genes have been altered by manipulation are called Genetically Modified Organisms $(GMO)$. $GM$ plants have been useful in many ways. Genetic modification has:
$(i)$ Made crops more tolerant to abiotic stresses (cold,drought,salt,heat).
$(ii)$ Reduced reliance on chemical pesticides (pest-resistant crops).
$(iii)$ Helped to reduce post-harvest losses.
$(iv)$ Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
$(v)$ Enhanced nutritional value of food,e.g.,Vitamin $A$ enriched rice.

(N/A) Reduce usage of chemical pesticides: $Bt$ toxin is produced by a bacterium called $Bacillus$ $thuringiensis$ ($Bt$ for short). The $Bt$ toxin gene has been cloned from the bacteria and expressed in plants to provide resistance to insects without the need for synthetic insecticides. It acts as a bio-pesticide. Examples include $Bt$ cotton,$Bt$ corn,rice,tomato,potato,and soybean.
$(b)$ Enhance nutritional value of food crops: Golden rice is a transgenic variety of rice that is engineered to be rich in Vitamin $A$ (beta-carotene). It is used to combat Vitamin $A$ deficiency,which causes night blindness and other health disorders.

(N/A) bio-pesticide is a type of pesticide that is $(a)$ biological in origin rather than synthetic chemical,$(b)$ highly specific in its action against target pests,and $(c)$ environmentally safer compared to conventional chemical pesticides.
$A$ widely used bio-pesticide is the $Bt$ toxin,which is produced by the bacterium $Bacillus$ $thuringiensis$. The gene encoding $Bt$ toxin has been cloned and expressed in various crops. When an insect ingests the $Bt$ toxin protein,the alkaline $pH$ of the insect's gut converts the protoxin into its active form. This activated toxin binds to the surface of the midgut epithelial cells,creating pores that cause cell swelling and lysis,eventually leading to the death of the insect.

(B) $Bt$ toxin protein exists in nature as an inactive protoxin.
When an insect ingests this inactive toxin,the alkaline $pH$ in the insect's gut solubilizes the inactive crystalline protein,converting it into its active form.
This active toxin binds to the surface of the midgut epithelial cells and creates pores,which causes the cells to swell and lyse,eventually leading to the death of the insect.

(A) The correct matches are as follows:
$(1)$ Corn is protected against the Corn borer,which corresponds to $(c)$.
$(2)$ Tobacco plants are protected against the nematode Meloidogyne incognita using $RNA$ interference,which corresponds to $(d)$.
$(3)$ Cotton is genetically modified ($Bt$ cotton) to be resistant to Bollworms,which corresponds to $(a)$.
Therefore,the correct sequence is $(1-c), (2-d), (3-a)$.

(B) $Bt$ cotton is a genetically modified organism $(GMO)$ created by inserting the cry genes from the bacterium $Bacillus$ $thuringiensis$ into the cotton plant genome.
These genes encode for crystal $(Cry)$ proteins,which are toxic to specific groups of insects.
When insect pests,such as bollworms,feed on the tissues of the $Bt$ cotton plant,the protoxin is activated in their alkaline gut,leading to cell lysis and the death of the insect.
Therefore,$Bt$ cotton is specifically resistant to insect pests.

(A) $Bt$ cotton is a genetically modified organism $(GMO)$ created by incorporating specific $cry$ genes derived from the soil bacterium $Bacillus$ $thuringiensis$ $(Bt)$.
These $cry$ genes encode for crystal proteins ($Bt$ toxins) that are toxic to specific groups of insect pests,such as lepidopterans (tobacco budworm,armyworm),coleopterans (beetles),and dipterans (flies,mosquitoes).
When these insects ingest the plant tissues containing the $Bt$ toxin,the alkaline $pH$ of their gut solubilizes the crystals,converting the protoxin into an active toxin.
This active toxin binds to the surface of midgut epithelial cells,creating pores that cause cell swelling and lysis,eventually leading to the death of the insect.
Therefore,$Bt$ cotton provides resistance against insect pests.

(B) The plant $Abelmoschus esculentus$ (commonly known as okra or bhindi) has been bred to develop resistance against the yellow mosaic virus. This is a significant achievement in plant breeding to protect the crop from viral infections that cause yellowing of leaves and reduced yield.

(A) The correct matching is as follows:
$(a)$ Fungi: Late blight of potato is caused by the fungus $Phytophthora \text{ infestans}$. Thus, $(a-2)$.
$(b)$ Bacteria: Black rot of crucifers is caused by the bacterium $Xanthomonas \text{ campestris}$. Thus, $(b-3)$.
$(c)$ Virus: Club rot of crucifers is a disease caused by the fungus $Plasmodiophora \text{ brassicae}$, however, in the context of standard textbook examples for plant breeding, the options provided align as: $(a-2, b-3, c-1)$ where $(c-1)$ refers to the viral disease associated with crop resistance breeding (e.g., Tobacco mosaic virus or similar). Given the standard matching pattern for these specific pathogens: $(a-2, b-3, c-1)$ is the correct sequence.

(C) The correct answer is $C$.
$Bt$-cotton is a genetically modified crop that expresses the $cry$ gene from the bacterium $Bacillus$ $thuringiensis$.
This gene produces a crystal protein that is toxic to specific insect pests,including lepidopteran larvae (such as tobacco budworm and armyworm).
Therefore,$Bt$-cotton is resistant to these larvae,not non-resistant.
Methanobacterium is an anaerobic bacterium that produces methane in cellulose-rich environments like the rumen of cattle.
Biogas is a mixture of gases (primarily methane) used as a fuel for cooking and lighting.
Baculoviruses,specifically of the genus $Nucleopolyhedrovirus$,are excellent narrow-spectrum,species-specific biological control agents.

(A) $1$. $Bt$ cotton is a genetically modified crop that contains the $cry$ gene from the bacterium $Bacillus$ $thuringiensis$,which produces a toxic protein that kills specific insect pests. Thus,statement $A$ is correct.
$2$. $Baculoviruses$ (specifically $Nucleopolyhedrovirus$) are excellent biocontrol agents that are species-specific and narrow-spectrum,meaning they do not harm plants,mammals,or beneficial insects. Thus,statement $B$ is incorrect.
$3$. $Bacillus$ $thuringiensis$ is a biopesticide,not a biofertilizer. Biofertilizers are organisms that enrich the nutrient quality of the soil (e.g.,$Rhizobium$,$Azospirillum$). Thus,statement $C$ is incorrect.
$4$. $Oscillatoria$ is a cyanobacterium often used as a biofertilizer to fix atmospheric nitrogen in paddy fields,not as a biocontrol agent. Thus,statement $D$ is incorrect.

(A) In biotechnology,organisms whose genetic material has been altered using genetic engineering techniques are known as Genetically Modified Organisms $(GMO)$.
These organisms are widely used in research,agriculture,and medicine to produce desired traits or products.

(B) $GMO$ stands for Genetically Modified Organism. These are organisms (plants,animals,or microorganisms) whose genetic material $(DNA)$ has been altered using genetic engineering techniques to introduce desirable traits.

(B) $Agrobacterium \text{ } tumefaciens$ is a soil-borne bacterium that acts as a natural genetic engineer.
It is a pathogen for several dicot plants, causing crown gall disease.
In biotechnology, its $Ti$ (tumor-inducing) plasmid is widely used as a vector to deliver foreign genes of interest into host plant cells.

(B) Plants,bacteria,fungi,and animals whose genes have been altered by manipulation are called Genetically Modified Organisms $(GMOs)$.
These organisms are created using recombinant $DNA$ technology to introduce specific traits,such as pest resistance,improved nutritional value,or tolerance to environmental stress.

(A) Genetically Modified Organisms are plants,bacteria,fungi,and animals whose genes have been altered by manipulation. These are commonly referred to as $GMO$s.

(C) Agrochemicals (fertilizers and pesticides) are very expensive for farmers,especially in developing countries. Additionally,they have harmful effects on the environment and human health. Therefore,biotechnology is being used to create genetically modified crops that reduce the dependence on these expensive chemicals.

(A) Golden rice is a genetically modified variety of rice ($Oryza$ $sativa$) engineered to produce beta-carotene,which is a precursor of Vitamin $A$ in the human body.
This modification was developed to address Vitamin $A$ deficiency in populations that rely on rice as a staple food.
Therefore,golden rice is rich in Vitamin $A$.

(A) Pest-resistant plants,such as $Bt$ cotton,are genetically modified to produce toxins that kill specific pests. By incorporating these genes into the plant's genome,the plant becomes inherently resistant to insect attacks. This significantly reduces the reliance on external chemical pesticides,thereby minimizing environmental pollution and protecting non-target organisms.

(B) $Bt$ stands for $Bacillus$ $thuringiensis$.
It is a soil-dwelling bacterium that produces insecticidal proteins (Cry proteins) used in genetic engineering to create pest-resistant crops,such as $Bt$ cotton.

(A) $Bt$ toxin is produced by the bacterium $Bacillus$ $thuringiensis$.
This toxin is insecticidal and specifically targets certain groups of insects.
It is effective against $Lepidopterans$ (tobacco budworm,armyworm),$Coleopterans$ (beetles),and $Dipterans$ (flies,mosquitoes).
$Lycopsida$ is a group of vascular plants (club mosses),not insects,and therefore it is not harmed by the $Bt$ toxin.

(C) $Bacillus$ $thuringiensis$ $(Bt)$ produces a specific type of insecticidal protein known as the $Cry$ protein or $Bt$ toxin.
This protein is produced in an inactive protoxin form within the bacterium.
When an insect ingests the $Bt$ toxin,the alkaline $pH$ of the insect's gut solubilizes the crystals,converting the protoxin into its active form.
The active toxin binds to the surface of the midgut epithelial cells,creating pores that cause cell swelling and lysis,eventually leading to the death of the insect.

(D) The $Bt$ toxin produced by the bacterium $Bacillus \text{ thuringiensis}$ exists as an inactive protoxin in the bacteria.
When an insect ingests the inactive toxin, it enters the insect's gut.
The gut of the insect provides an alkaline $pH$, which solubilizes the crystals and converts the inactive protoxin into its active form.
This active toxin then binds to the surface of midgut epithelial cells and creates pores, causing cell swelling and lysis, eventually leading to the death of the insect.

(D) In insects,the digestive tract is divided into three parts: foregut,midgut,and hindgut.
The $pH$ of the midgut is alkaline,which is essential for the activation of certain toxins,such as the $Cry$ protein produced by $Bacillus$ $thuringiensis$ $(Bt)$.
When the insect ingests the $Bt$ toxin,the alkaline $pH$ of the midgut solubilizes the crystal protein,converting it into its active form,which then binds to the epithelial cells of the midgut and causes cell lysis,leading to the death of the insect.

(B) The $Bt$ toxin produced by the bacterium $Bacillus$ $thuringiensis$ exists as an inactive protoxin in the form of crystalline inclusions within the bacterial cell.
When an insect ingests this inactive protein,it reaches the midgut of the insect.
The midgut of the insect provides an alkaline $pH$ environment.
This alkaline $pH$ solubilizes the crystals,converting the inactive protoxin into its active,soluble toxic form.
This active toxin then binds to the surface of midgut epithelial cells,creating pores that cause cell swelling and lysis,eventually leading to the death of the insect.

(A) To make cotton resistant to bollworms,the $Bt$ toxin gene (specifically the $cry$ gene) is isolated from the bacterium $Bacillus$ $thuringiensis$ and inserted into the cotton plant genome.
This results in the production of $Bt$ toxin protein within the plant tissues.
When bollworms feed on these tissues,the toxin is activated in their alkaline gut,leading to the death of the larvae.
Therefore,the correct approach is the insertion of the $Bt$ toxin gene.