Genetic engineering techniques and critical evaluation
Inheritance, variation and evolution • Variation and evolution
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Definition and scope of genetic engineering
Genetic engineering is the alteration of an organism’s genome by inserting one or more genes from another organism into its DNA. The inserted gene provides the code for protein synthesis in the host, producing a trait that the host did not previously express. When a gene from one species is inserted into another, the resulting organism is transgenic and expresses the protein coded by the foreign gene .
Main laboratory steps in genetic engineering (HT only)
The process begins with identification and isolation of the target gene from donor DNA using restriction enzymes or other gene‑editing tools. The donor gene is cut from the source genome and prepared with compatible ends. A vector, commonly a bacterial plasmid or a virus, is cut open with the same restriction enzyme and the donor gene is inserted and sealed using DNA ligase. The vector delivers the recombinant DNA into host cells by transformation (bacteria), transfection (cells) or other delivery methods. Host cells that incorporate the vector express the new gene and produce the encoded protein. Selection markers and reporter genes identify successful transformants, and large-scale growth produces the desired product, as in bacterial production of human insulin .
Mechanisms of gene delivery and expression
Vectors act as carriers of recombinant DNA into host organisms. Plasmids provide circular DNA that transfers easily between bacteria and act as stable expression systems for proteins. Viruses can act as vectors in eukaryotic cells by delivering genetic material into nuclei. Successful expression requires promoter sequences, correct coding sequence, and host cell machinery for transcription and translation. Lack of compatible regulatory sequences or incompatible host machinery limits expression and can prevent the desired trait from appearing.
Benefits in agriculture and medicine
Genetic engineering increases crop yields and nutritional value by adding traits such as drought tolerance, pest resistance or vitamin production, for example drought-resistant maize and golden rice containing carotene to reduce vitamin A deficiency . Medical applications include producing human proteins (insulin, clotting factors) in bacteria or animals, which reduces allergic reactions and increases supply; genetically engineered sheep can produce therapeutic proteins in milk .
Risks, limitations and uncertainties
Gene transfer carries ecological risks such as gene flow from GM crops into wild relatives and emergence of herbicide-resistant weeds if resistance genes escape. Health concerns include potential allergenicity and long-term effects that require monitoring. Technical limitations include incomplete expression, off-target effects, and the development of resistance in pests or pathogens. Regulatory frameworks and containment measures reduce but do not eliminate these risks, so risk assessments must consider probability and scale of possible harms .
Evaluation, ethics and making judgements
Evaluation of genetic engineering requires interpretation of empirical evidence (yield data, ecological monitoring, clinical trials) and assessment of social, ethical and economic factors. Moral objections include concerns about interfering with natural organisms and religious beliefs. Practical judgements require weighing saved lives and improved nutrition against environmental risks and socioeconomic impacts such as corporate control of seed supplies. Evidence-based policy and transparent risk–benefit analysis provide the basis for informed decisions about cloning and GM crops .
Key notes
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