Biotechnology: UPSC Previous Year Questions (Science and Technology)

Explanation

Stem cells are undifferentiated cells with the potential to develop into various specialized cell types, offering promise for regenerative medicine and disease treatment

Statement 1 and 2 are incorrect: The blastocyst stage of embryos is a common source of embryonic stem cells, but it is not the only source. Stem cells can also be derived from adult tissues (adult stem cells) and umbilical cord blood. As of current techniques, obtaining embryonic stem cells typically requires the destruction of the blastocyst. Alternative methods are being actively researched to derive stem cells without causing harm to the blastocyst.

Statement 3 is correct: Stem cells, such as embryonic stem cells have the ability to self-renew and regenerate themselves in vitro indefinitely under appropriate conditions. This property makes them valuable for research and therapeutic applications.

Statement 4 is correct: Indian research centers, such as the National Centre for Biological Sciences (NCBS) and the Indian Council of Medical Research (ICMR), have successfully created a few stem cell lines capable of differentiating into multiple tissue types.

Explanation

Monsanto, an American multinational company, developed an insect-resistant cotton variety known as Bt cotton. This transgenic cotton incorporates a gene from the bacterium Bacillus thuringiensis (Bt), enabling the plant to produce Bt toxins that are effective against specific insect pests, particularly lepidopteran larvae like the cotton bollworm. The introduction of the Bt gene allows the cotton to produce its own insecticide, reducing the need for external chemical insecticides.

Explanation

DNA fingerprinting is biotechnique based on analysis of specific regions of DNA that are unique to each individual. This makes it a powerful forensic tool. Assertion (A) is true: DNA fingerprinting, also known as DNA profiling, has become a powerful tool in forensic science for identifying individuals. It is widely used to establish paternity and to identify suspects in criminal cases, including rape and assault. The unique genetic makeup of each individual allows forensic experts to match DNA samples from crime scenes with those of suspects or to determine biological relationships. Reason (R) is true: Trace evidence such as hair, saliva, and dried semen can provide sufficient DNA for analysis. Even small biological samples left at crime scenes can be collected and processed to extract DNA, which can then be compared to known samples to identify individuals. Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains why DNA fingerprinting is effective in establishing paternity and identifying criminals in rape and assault cases. The ability to analyze DNA from minimal trace evidence underpins the power of DNA fingerprinting in forensic investigations.

Explanation

Insect-resistant cotton, commonly known as Bt cotton, has been genetically engineered by inserting a gene from the bacterium Bacillus thuringiensis (Bt). This bacterium naturally produces a protein toxic to specific insect pests, such as bollworms, but is safe for humans and non-target organisms. The Bt gene produces a protein that disrupts the digestive system of the pests upon ingestion, ultimately killing them. Bt cotton has significantly reduced the dependence on chemical insecticides and has become a widely adopted technology for pest management in cotton farming.

Explanation

Option (a) is correct: Hybridoma technology is a groundbreaking biotechnological method developed for the large-scale production of monoclonal antibodies. This technique involves the fusion of an antibody-producing B lymphocyte with a myeloma (cancer) cell, creating a hybrid cell line called a hybridoma. These hybridomas are capable of producing a single type of antibody (monoclonal) indefinitely. Monoclonal antibodies are widely used in medical diagnostics, treatment of diseases such as cancer and autoimmune disorders, and in research applications. Options (b), (c) and (d) are incorrect:

Interferons, are proteins used in antiviral therapies. They are not produced using hybridoma technology. They are typically synthesized using recombinant DNA technology. Antibiotics are derived from microorganisms like fungi and bacteria, not via hybridoma technology. Alcohol production relies on fermentation processes, not hybridoma technology.

Explanation

The introduction of the Bt gene into the cotton genome provides effective protection against damage caused by insects, significantly reducing the need for chemical pesticides. Assertion (A) is true: Insect-resistant transgenic cotton, known as Bt cotton, has been developed by inserting the Bt gene into cotton plants. Reason (R) is true: This gene, derived from the bacterium Bacillus thuringiensis, enables the plant to produce a protein toxic to specific insect pests, such as bollworms, while being harmless to humans and non-target organisms. Since the Bt gene’s origin from Bacillus thuringiensis directly explains its role in imparting insect resistance. Hence, both the assertion and the reason are true, and the reason correctly explains the assertion.

Explanation

Cloning is the process of creating genetically identical copies of an organism, cell, or DNA sequence. It can be natural (as in identical twins) or artificial (like somatic cell nuclear transfer, used in Dolly the sheep). Assertion (A) is true: Dolly the sheep, born in 1996, was the first mammal successfully cloned from an adult somatic cell, making her a landmark achievement in biotechnology. Reason (R) is false: Dolly was not produced through in vitro fertilization (IVF), which involves the fusion of sperm and egg outside the body. She was created using somatic cell nuclear transfer (SCNT), a process in which the nucleus of a somatic cell (in Dolly’s case, a mammary gland cell) was transferred into an enucleated egg cell (an egg cell with its nucleus removed). The resulting cell was stimulated to divide and develop into an embryo, which was then implanted into a surrogate sheep for gestation.

Explanation

Options (a), (b) and (c) are incorrect: Protein analysis lacks the precision needed for identifying individual genetic relationships, as protein expression can be influenced by multiple factors. Chromosome counting determines the number of chromosomes but cannot identify specific genetic relationships. Quantitative analysis of DNA measures the quantity of DNA but does not provide the unique genetic markers necessary for establishing paternity.

Option (d) is correct: DNA fingerprinting is the most accurate and reliable technique to establish paternity. This method analyzes specific regions of the DNA that are highly variable among individuals, called short tandem repeats (STRs). A child inherits half of their DNA from the mother and the other half from the father, making DNA fingerprinting a powerful tool to match the genetic profiles of the child and the alleged parent.

Explanation

DNA damage and permanent mutations are likely in professionals exposed to mutagenic agents like radiation, toxic chemicals, or hazardous environments.

Statement 1 is correct: Researchers using Carbon-14 isotopes are exposed to beta radiation from the radioactive isotope. Prolonged exposure can damage DNA and increase the risk of mutations.

Statement 2 is correct: X-ray technicians are at risk due to ionizing radiation, which can break DNA strands and cause chromosomal abnormalities. Protective measures like lead aprons are essential to minimize exposure.

Statement 3 is incorrect: While coal miners are exposed to harmful substances like coal dust and radon gas, these hazards are more strongly linked to respiratory diseases (e.g., black lung disease) and lung cancer, rather than direct, widespread DNA changes. Hence, it may not be included as a primary factor for widespread DNA changes.

Statement 4 is correct: Chemicals found in dyes and paints, such as benzene and lead-based compounds, can be harmful. They can cause cell damage and increase the risk of DNA changes. Long-term exposure is linked to a higher risk of cancer.