6.2.2Global Challenges
Genetic Engineering — OCR Gateway GCSE Combined Science A J250 - Biology Revision Notes & Topical Questions
5 min read 9 parts Lesson 6 of 18
Part 1 of 7What is genetic engineering?
Genetic engineering is the modification of an organism's genome by introducing a gene from another organism to give a desired characteristic. The resulting organism is described as transgenic or genetically modified (GM). Unlike selective breeding, genes can be transferred between very different species, and the change happens within a single generation.
Part 2 of 7The process
For crops and animals the gene is often transferred at an early stage of development, such as a fertilised egg or embryo, so that all the cells of the adult organism carry the new gene.
Part 3 of 7Examples
Part 4 of 7Benefits
Genetically modified crops can have increased yield, longer shelf life, improved nutrition, and resistance to insects, diseases and herbicides. This could improve food security in regions with limited food. Using bacteria to make human proteins avoids using animal sources, which may carry a risk of disease or provoke immune responses.
Part 5 of 7Concerns
Some people worry that eating GM food may harm human health, although evidence so far has not shown this.
- or that insects not intended as targets may be harmed, affecting food webs and biodiversity.
Part 6 of 7Applications and ethical evaluation
Genetic engineering has medical uses as well as agricultural ones.
Researchers are also developing gene therapy, in which a healthy allele is inserted into the cells of a person with an inherited disorder such as cystic fibrosis.
When asked to evaluate genetic engineering, give a balanced answer.
- and objections that it is unnatural to move genes between species.
The topic links to selective breeding (compare the two methods), to enzymes (restriction enzymes and ligase are enzymes with specific active sites) and to protein synthesis, because the gene must be expressed in the new host.
Part 7 of 7Exam-style questions
Describe how a gene for insect resistance could be transferred into a crop plant. [4]4 marks
Cut the gene from the donor organism using restriction enzymes (1). Insert it into a vector such as a plasmid or virus, using ligase (1). The vector introduces the gene into plant cells, often at an early stage of development (1). The plant cells grow into a plant in which all cells contain the gene and make the toxin (1).
Give two possible benefits and one concern of growing genetically modified crops. [3]3 marks
Benefits (any two): higher yield; added nutrients; resistance to pests, disease or herbicide (2). Concern (any one): gene transfer to wild plants; harm to other organisms or biodiversity; unknown effects on health (1).
Explain why genetic engineering is faster than selective breeding. [2]2 marks
In genetic engineering the required gene is transferred directly (1) so the new characteristic appears in one generation, whereas selective breeding needs many generations of breeding to increase the allele frequency (1).
Key terms
| Term | Meaning |
|---|---|
| Genetic engineering | Transferring a gene from one organism into another to give a new characteristic. |
| Restriction enzyme | An enzyme that cuts DNA at a specific base sequence. |
| Ligase | An enzyme that joins pieces of DNA together. |
| Vector | A carrier, such as a plasmid or virus, used to insert a gene into a cell. |
| Plasmid | A small circular loop of DNA found in bacteria. |
| Transgenic | An organism containing a gene from another species. |
| GM crop | A crop plant whose genome has been modified by genetic engineering. |
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