Genetic Engineering

Expression means the gene produces a protein or useful product. For exams connect gene expression with a functional gene.

Direct answer: Option A is correct. A terminator sequence normally signals that transcription or gene expression should stop at a particular point. In simple terms, genetic information is read to make an RNA molecule and, when applicable, a protein. The terminator acts like a stop instruction so the reading process ends at the proper place rather than continuing unnecessarily. The exact molecular details can differ between systems, but the general school-level role is termination of transcription or expression. Option A works because it describes this stop signal. Option B, giving light to a cell, is not the function of a DNA terminator; light production, when present in biotechnology, depends on particular genes and proteins. Option C, making RNA into fat, is not a definition of a terminator sequence and confuses genetic information with metabolism. Option D, making DNA into salt, is biologically meaningless and does not describe nucleic-acid regulation. Therefore the stated answer is sound. Memory trick: promoter means start, terminator means stop; do not confuse a terminator with a gene that produces a visible marker.

To obtain a desired gene DNA is first extracted from the source. For exams consider gene isolation to begin with DNA extraction.

Gene gun delivers DNA into cells using tiny particles. For exams remember it as a direct gene transfer method.

In microinjection DNA is directly introduced into a cell. For exams remember it as a direct method.

Electroporation creates temporary pores in the membrane using electric pulses. For exams remember it as a helper for DNA entry.

Recombinant DNA technology mainly involves cutting and joining DNA. For exams remember restriction enzyme and ligase as key enzymes.

Direct answer: Option A, gene, is correct. A gene is a particular stretch of DNA that contains hereditary information. That information may provide instructions for making a specific protein or may help determine a characteristic or trait through a biological process. Start from the basic idea: DNA is a long molecule made of information-bearing sequences; a gene is one meaningful information unit within that DNA. When a gene is expressed, its information can be copied into RNA and used in producing a protein, although not every gene directly codes for a protein. Option A is therefore the scientifically appropriate term. Option B, water, is a substance and not an information-carrying DNA segment. Option C, lipid, is a type of biological molecule used in membranes and other functions, not the name of a DNA information unit. Option D, mineral, is an inorganic nutrient or material and cannot mean a coded region of DNA. The wording says “for a specific protein,” so gene is the expected answer, even though genes may also code for functional RNA. Memory cue: DNA is the information library; a gene is one instruction or entry in that library.

Escherichia coli is a common host due to fast growth and easy handling. For exams remember it as a bacterial host.

An antibiotic resistance gene helps select transformed cells. For exams remember it as an example of selectable marker.

A cell that takes up a recombinant plasmid is called transformed. For exams remember the link between transformation and transformed cell.

Safety rules reduce uncontrolled effects and risks. For exams connect biosafety with responsible use.

Gene therapy tries to correct problems caused by faulty genes. For exams remember it as a medical application.

Viral vectors can deliver genetic material into cells. For exams remember them as gene delivery tools.

DNA sequencing reveals the exact order of bases. For exams connect it with gene identification and analysis.

Restriction enzymes cut DNA at specific sites. For exams carefully match enzymes with their functions.

Gel electrophoresis is used to separate DNA fragments not for protein synthesis. For exams remember the main use of each technique.

Direct answer: Option A is correct. In genetic engineering, a foreign gene means a gene introduced from another organism or source into the organism being modified. It is selected because its DNA sequence carries instructions for a desired product or characteristic, such as production of a useful protein, resistance to a condition, or another planned trait. The reasoning is: first identify the required trait; then find a gene associated with that trait; then introduce and express it in a suitable host, if the technique is successful. Option A states the real purpose of choosing the foreign gene. Option B is wrong because a gene is not selected because it is always colorless; colour is not the general criterion. Option C is wrong because genes do not all make water, and water production is not the aim of genetic engineering. Option D is wrong because stopping sound is unrelated to the genetic information being selected. The exact result depends on the gene, host and regulation, so “desired trait” is the correct general answer, not a claim that success is automatic. Memory cue: choose the gene for the feature you want.

A recombinant plasmid is introduced into a host cell so it can replicate or express. For exams remember the order as joining gene then inserting into host.

Genetic engineering can produce crops with useful traits. For exams remember both agricultural and medical applications.

Ethidium bromide helps visualize DNA fragments. For exams connect it with DNA detection in gels.

Origin of replication allows copies of vector DNA to form. For exams connect it with plasmid replication.

Reverse transcriptase makes complementary DNA from RNA. For exams connect it with cDNA synthesis.

Calcium chloride treatment makes bacterial cells able to take up DNA. For exams connect it with competent cell preparation.

A competent cell is able to take up external DNA. For exams remember it as a cell ready for transformation.