NCERT Solutions For Class 12 Biology Chapter 12

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Important Terms Related To Chapter 12

1. Cry Gene: The Bt toxins are coded by a gene named Cry.
2. Cry Protein: The insecticidal protein which is produced by Bacillus thuringiensis.
3. Biopesticides: Biological agents that are used to control weeds, insects and other pests.
4. Genetically Modified Organisms (GMO): The organisms which have altered genes in them. These are also known as transgenic organisms. e.g. Bt Cotton, Bt Corn, Transgenic rat, Transgenic cow-Rosie
5. Sustainable Agriculture: It involves organic farming and other integrated management practices which maintain soil fertility while increasing crop productivity.
6. RNA Interference (RNAi): Process used to develop pest resistant plants. It involves silencing of a specific mRNA due to complementary double stranded RNA.

More To Know

1. Bt. Cotton: The soil bacterium Bacillus thuringiensis produced crystal protein called cry protein that kills certain insect’s larvae such as tobacco budworm, armyworm, beetles and flies.
2. Bt toxin genes were isolated form Bacillus thuringiensis and incorporated into the several crop plants such as cotton.
3. The proteins encoded by the genes: CrylAc and CryllAb control the cotton bollworms and CrylAb controls corn borer.
4. Bt. toxin protein exists as inactive pro-toxins, but once an insect ingest this inactive toxin, it is converted into active form of toxin due to the alkaline pH of the gut which solubilize the crystal. This causes swelling and lysis of epithelial cells of midgut leading to death of insect larvae.

Gene Therapy

1. It is a technique of inserting genes into the cells and tissue of an individual to treat a hereditary disease.
2. The first clinical gene therapy was given in 1990 to a four year old girl with adenosine deaminase (ADA) deficiency. ADA enzyme is required for proper functioning at immune system.
3. As these cells are not immortal, the patient required periodic infusion of such genetically engineered lymphocytes.
4. If a functional gene is Introduced into a bone marrow cells at early embryonic stage. It could be a permanent cure of ADA deficiency.
5. This disorder is caused due to the deletion of the gene for adenosine deaminase enzyme. In some children ADA deficiency can be cured by bone marrow transplantation. Lymphocytes from the blood of patient are grown in a culture. A functional ADA cDNA is then introduced into these lymphocytes using retroviral vector. The lymphocytes are transferred into the body of patients.

Important Questions On 12th Biology Chapter 12

What are transgenic bacteria?

Transgenic bacteria contain foreign gene that is intentionally introduced into its genome. They are manipulated to express the desirable gene for the production of various commercially important products.

What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?

Cry proteins are encoded by cry genes. These proteins are toxins, which are produced by Bacillus thuringiensis bacteria. This bacterium contains these proteins in their inactive from. When the inactive toxin protein is ingested by the insect, it gets activated by the alkaline pH of the gut. This results in the lysis of epithelial cell and eventually the death of the insect. Therefore, man has exploited this protein to develop certain transgenic crops with insect resistance such as Bt cotton, Bt corn, etc.

What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.

Gene therapy is a technique for correcting a defective gene through gene manipulation. It involves the delivery of a normal gene into the individual to replace the defective gene, for example, the introduction of gene for adenosine deaminase (ADA) in ADA deficient individual. The adenosine deaminase enzyme is important for the normal functioning of the immune system. The individual suffering from this disorder can be cured by transplantation of bone marrow cells. The first step involves the extraction of lymphocyte from the patient’s bone marrow. Then, a functional gene for ADA is introduced into lymphocytes with the help of retrovirus. These treated lymphocytes containing ADA gene are then introduced into the patient’s bone marrow. Thus, the gene gets activated producing functional T- lymphocytes and activating the patient’s immune system.

Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil?

Recombinant DNA technology (rDNA) is a technique used for manipulating the genetic material of an organism to obtain the desired result. For example, this technology is used for removing oil from seeds. The constituents of oil are glycerol and fatty acids. Using rDNA, one can obtain oilless seeds by preventing the synthesis of either glycerol or fatty acids. This is done by removing the specific gene responsible for the synthesis.

Does our blood have proteases and nucleases?

No, human blood does not include the enzymes, nucleases and proteases. In human beings, blood serum contains different types of protease inhibitors, which protect the blood proteins from being broken down by the action of proteases. The enzyme, nucleases, catalyses the hydrolysis of nucleic acids that is absent in blood.

Consult internet and find out how to make orally active protein pharmaceutical. What is the major problem to be encountered?

Orally active protein pharmaceuticals contain biologically active materials such as peptides or proteins, antibodies, and polymeric beads. It is administrated orally into the body through various formulations. It involves the encapsulation of protein or peptide in liposomes or formulations using penetration enhancers. These proteins or peptides are used for treatment of various diseases and are also used as vaccines. However, the oral administration of these peptides or proteins has some problems related to it. Once these proteins are ingested, the proteases present in the stomach juices denature the protein. As a result, their effect will be nullified. Hence, it is necessary to protect the therapeutic protein from digestive enzymes, if taken orally. This is the reason for the proteins to be injected directly into the target site.

Find out from internet what is golden rice.

Golden rice is a genetically modified variety of rice, Oryza 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 betacarotene pigment in its leaves. However, it is absent in the endosperm of the seed. This is because beta-carotene pigment helps in the process of photosynthesis while photosynthesis does not occur in endosperm. Since beta-carotene is a precursor of provitamin A, it is introduced into the rice variety to fulfil the shortage of dietary vitamin A. It is simple and a less expensive alternative to vitamin supplements. However, this variety of rice has faced a significant opposition from environment activists. Therefore, they are still not available in market for human consumption.

Details: Parent Category: student Corner; Category: Class 12 Biology; Published: 16 May 2020; Hits: 51

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