Genetic Engineering

Correct answer: A. When it produces useful RNA or protein

Gene expression means producing a product from gene information. Getting the foreign gene product shows success.

Correct answer: A. To produce human-like insulin

The human insulin gene can be used to make human-like insulin. It is an important example of medical biotechnology.

Correct answer: A. Bacillus thuringiensis

Bt gene is related to the bacterium Bacillus thuringiensis. It is used in pest-resistant crops.

Correct answer: A. Transgenic plant

A plant is called transgenic when a gene from another organism is introduced and stably incorporated into its genome using genetic engineering. A hybrid plant is produced by crossing genetically different plants, so it is not necessarily transgenic. Exam tip: associate transgenic plants with the stable incorporation of a foreign gene and a possible new desired trait.

Correct answer: A. It can deliver DNA across the cell wall

Plant cell walls are rigid, so DNA delivery can be difficult. The gene gun delivers DNA using tiny particles.

Correct answer: A. Gene transfer in plants

Agrobacterium is a useful bacterium for delivering genes into plants. It is famous in plant genetic engineering.

Correct answer: A. To understand possible harms

Risk assessment helps understand effects on health and environment. It is part of safe biotechnology.

Correct answer: A. Unwanted microbes or DNA can distort the experimental results

Contamination may introduce unwanted microbes or foreign DNA into a culture or sample. This can produce false observations and make the detection or measurement of the desired gene, vector, or product unreliable. Option D is incorrect because contamination can significantly affect experimental validity. Exam tip: remember that aseptic technique and proper controls are essential in genetic engineering experiments.

Correct answer: A. Different

Most individuals have different DNA patterns. That is why DNA fingerprinting is useful for identification.

Correct answer: A. To identify an individual

In forensic science, a DNA profile is prepared from blood, hair, or other biological samples and compared with a suspect’s or reference sample. This helps identify an individual. The other options are unrelated to the forensic use of DNA technology. Exam tip: Associate DNA profiling with identification and the analysis of biological relationships.

Correct answer: A. To correct a disease related to a defective gene at gene level

Gene therapy aims to correct a problem at the gene level. Remember it as a possible medical application.

Correct answer: A. क्या जीन सफलतापूर्वक प्रविष्ट हुआ और अभिव्यक्त हो रहा है

Successful gene insertion and gene expression are separate issues. A DNA construct may fail to enter the host, may be lost, may be inserted in the wrong orientation or may remain silent even after entering the cell. Therefore, screening or verification should first establish that the intended recombinant cells contain the foreign gene; an expression test can then confirm production of the expected RNA or protein. Option A is the only scientifically relevant choice. Water colour, soil weight and the status of a light source do not indicate whether transformation or expression has occurred.

Correct answer: A. Because not all cells take up and stably maintain foreign DNA

Transformation efficiency is limited because not all host cells take up foreign DNA or maintain it stably. Selectable markers and screening are used to identify the successfully transformed cells. Option C is incorrect because some cells can take up foreign DNA when an appropriate transformation method is used. Exam tip: remember transformation as the entry and maintenance of foreign DNA in a host cell.

Correct answer: A. It can show copies formed from one successful transformed cell

A colony is often a group of cells grown from one cell. Correct colonies are selected to continue cloning.

Correct answer: A. Because many identical copies of a gene can be obtained for study

Gene cloning produces many identical copies of a selected gene. The increased amount of DNA makes it easier to study the gene’s sequence, structure and function and to use it in further experiments. The other options are incorrect because cloning is not intended to destroy the gene, remove all cellular DNA or permanently inactivate its protein. Exam tip: Remember that the key outcome of gene cloning is amplification of a desired gene.

Correct answer: A. To compare the result

A control group shows whether the change happened due to the experiment. Link it with fair comparison in exams.

Correct answer: A. Recombinant insulin

Recombinant insulin can be produced by genetic engineering. It is a useful product for human health.

Correct answer: A. To understand safety and effects

The correct answer is A: to understand safety and effects. Genetically modified organisms contain a deliberately changed genetic material, so their traits, benefits, and possible unintended effects must be studied carefully. A controlled environment limits uncontrolled spread and allows scientists to compare the modified organism with a suitable control under known conditions. They can observe growth, performance, interactions, and possible risks before wider use. Option A is correct because testing is meant to collect evidence about safety and effects. Option B is wrong because immediate release everywhere would remove careful control and could create ecological or health concerns. Option C is wrong because testing does not aim to remove the organism's DNA. Option D is wrong because the purpose is not always destruction; approved organisms may be useful after proper evaluation. Memory cue: test first, observe benefits and risks, then decide on responsible use.

Correct answer: A. To start gene expression

A promoter can control the start of gene expression. So it may be needed to produce a useful protein.

Correct answer: A. When the desired gene joins the correct vector and works in the host

For success, gene joining and its function in the host are both needed. Cutting alone is not enough.

Correct answer: A. They can join easily with complementary bases

Sticky ends have single-stranded overhangs that can pair with complementary ends. This makes DNA joining easier.

Correct answer: A. Sticky ends have single-stranded overhangs

The direct answer is A: sticky ends have single-stranded overhangs. DNA usually has two complementary strands. Some restriction enzymes cut the two strands at different positions, leaving a short unpaired extension. This extension can pair with a complementary extension on another DNA fragment; this is why it is called sticky. A blunt end is cut straight across both strands, so it has no single-stranded overhang. Option A is correct because it describes the structural difference exactly. Option B is wrong because blunt ends are DNA ends, not proteins. Option C is wrong because sticky ends are still parts of DNA. Option D is wrong because the two types differ in their structure and in how easily they join. Memory cue: sticky means an exposed matching overhang; blunt means a straight cut.

Correct answer: A. PCR

The direct answer is A: PCR is most useful when the DNA sample is very small. PCR, or polymerase chain reaction, is an in-vitro method that amplifies a selected DNA region. Its basic cycle is: denaturation separates the two DNA strands; primers attach to the target boundaries during annealing; a thermostable DNA polymerase extends the primers during extension. Repeating the cycle produces approximately exponential amplification of the selected region, provided suitable primers and a usable template are present. Option A is correct because even a small starting amount can yield many copies for testing. Option B, simple filtration, separates particles but does not copy DNA. Option C, boiling, may separate strands or damage biological material but does not specifically amplify DNA. Option D, drying, removes water and does not create DNA copies. Memory cue: PCR is a DNA photocopier, not a filter or heater.

Correct answer: A. Phosphate groups

Phosphate groups give DNA its negative charge. Therefore, DNA moves toward the positive electrode in an electric field.

Correct answer: A. A good vector needs features like origin of replication and selectable marker

Not every plasmid is suitable for cloning. A good vector should have required features for identification and replication.