Genetic Engineering

Ti plasmid is found in Agrobacterium and is linked with plant gene transfer. In exams relate (Ti) to tumor inducing.

E. coli is a bacterium that grows rapidly in the laboratory, is easy to culture, and has a well-studied genetic system. Desired genes can be introduced into it using vectors such as plasmids. Therefore, option A is correct; E. coli is not restricted to plants, nor is it a virus or a DNA-free organism. Exam tip: Remember E. coli as a common bacterial host in genetic engineering.

A foreign gene is inserted into a host from outside. In exams it is also called gene of interest.

Gene of interest carries the useful trait we want. It is the main part of recombinant DNA in exams.

The direct answer is A, formation of a useful product from gene information. A gene stores information in a DNA sequence. Gene expression means that this information is used by a cell. Usually DNA information is first copied into RNA by transcription, and the RNA may then be used to make a protein by translation. Some genes produce functional RNA rather than a protein, so the broad meaning is production of a useful RNA or protein product. Option A is correct because it expresses this complete idea in simple words. Option B is wrong because genes do not have a biological process called changing colour as gene expression. Option C is wrong because DNA is not converted into water; DNA remains a nucleic acid. Option D is unrelated: an empty cell is not the meaning of using gene information. The exam cue is: gene expression means a gene is switched on and its information produces RNA or protein.

A promoter is the DNA region where transcription begins. For exams think of it as a gene on signal.

A reporter gene can give a visible signal. Remember it as a gene that gives a detection signal.

Recombinant DNA technology has been used to produce human insulin. It is a famous medical example in exams.

Bt cotton contains an insect resistance gene from (Bt) bacterium. Link (Bt) with Bacillus thuringiensis in exams.

PCR makes many copies even from a small amount of DNA. Remember its use in forensics and diagnosis.

DNA fingerprinting compares DNA patterns of individuals. Remember uses in identification and paternity testing.

Biosafety is important because genetic engineering can create organisms or biological materials with characteristics that must be assessed and controlled before they are used, released or transferred. Biosafety procedures include risk assessment, suitable containment, careful handling, prevention of accidental release, monitoring and responsible disposal. They protect laboratory workers, nearby communities, animals, plants and the environment while supporting valid scientific research. Therefore option A is correct: the purpose is the safe use and control of genetically modified organisms and related materials. Biosafety does not make DNA sweet, decorate a laboratory or keep an electrophoresis gel colourless. The governing concept is precautionary management of biological risks, not improvement of appearance or taste.

Bioethics focuses on social and ethical aspects of technology. Responsible use is the key exam point.

Restriction enzyme names are based on their source bacteria. Remember examples like EcoRI for exams.

The direct answer is A, restriction endonuclease. EcoRI is an enzyme obtained from Escherichia coli. It recognises a particular short DNA sequence, called its recognition site, and cuts DNA at a defined position within or near that site. Because it cuts within a DNA molecule, it is called an endonuclease. Its specific cutting action is useful in recombinant-DNA technology for removing or inserting DNA fragments. Option A is correct because EcoRI is a famous restriction endonuclease. Option B, DNA ligase, does the opposite job: it joins DNA fragments by forming bonds in the sugar-phosphate backbone. Option C, amylase, digests starch and is not a DNA-cutting enzyme. Option D, lipase, digests fats, not DNA. A useful memory cue is ‘restriction cuts, ligase links’: restriction enzymes cut at recognised sequences, while ligase joins compatible DNA ends.

“Endo” means “within” or “inside.” Therefore, an endonuclease can cleave phosphodiester bonds within a nucleic acid chain, whereas an exonuclease generally removes nucleotides from an end. Exam tip: remember endo = inside and exo = outside/from the end.

An exonuclease removes nucleotides sequentially from the free 5′ or 3′ ends of a DNA polynucleotide chain. In contrast, an endonuclease cuts within the DNA molecule, so option B is incorrect. Exam tip: remember “exo” as acting from the outside or end.

DNA polymerase adds nucleotides during new DNA strand formation. Remember it as a DNA synthesis enzyme.

A plasmid can make copies inside the host cell. Remember small circular DNA and independent replication for exams.

A cloning vector needs (ori) for replication. In exams (ori) and selectable marker are both important.

The correct answer is A: complementary ends form, so joining becomes easier. A restriction enzyme cuts DNA at a particular recognition sequence. When the DNA fragment and vector are cut with the same enzyme, their exposed single-stranded ends are usually compatible, often called sticky ends. The matching bases can pair by hydrogen bonds, and DNA ligase can seal the remaining breaks to make recombinant DNA. Option A is correct because matching ends bring the two DNA pieces together in the proper construction step. Option B is wrong because restriction enzymes cut DNA at specific sites; they do not always destroy both molecules. Option C is wrong because cutting DNA does not always stop protein formation; the result depends on the gene and cell. Option D is wrong because the DNA molecule does not change colour merely because it was cut. Memory cue: same cutter, compatible ends, easier joining.

The correct answer is A: sterile tools prevent contamination by unwanted microorganisms. Genetic-engineering experiments use small amounts of DNA, cells, and carefully selected cultures. If bacteria, fungi, or other unwanted microbes enter through dirty tools, they may grow, consume nutrients, alter the culture, or introduce unwanted DNA. Then the observed result may not come from the intended experiment. Sterilisation and aseptic handling reduce this risk. Option A is correct because cleanliness protects the sample and improves reliability. Option B is wrong because DNA has no need to become sweet and sterility does not add taste. Option C is wrong because sterile tools do not change an enzyme's colour. Option D is wrong because sterilisation does not turn gel into stone; gels are prepared with particular chemicals and conditions. Exam cue: sterile means free from unwanted living contaminants, not chemically sweeter or harder.

Useful proteins like insulin can be made through gene expression. Treat recombinant insulin as a key example in exams.

Recombinant DNA is formed by joining DNA pieces from different sources. It is a key idea in gene cloning.

Restriction enzymes cut DNA at specific recognition sites. They are often called molecular scissors.