Genetic modification changes an organism's genetic material one gene at a time. Bacteria given a human gene make human insulin; crop plants given new genes resist herbicides or insect pests, or become more nutritious. Extended: the cut-and-paste steps with restriction enzymes and DNA ligase, and the case for and against GM crops.
Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes. Examples: human genes inserted into bacteria to produce human proteins such as insulin; genes inserted into crop plants to give resistance to herbicides or insect pests, or to improve nutritional qualities. Extended: a human gene is cut out with restriction enzymes, leaving sticky ends; a plasmid is cut with the same enzyme; DNA ligase joins them into a recombinant plasmid, which is put into bacteria that multiply and express the gene.
Fig. 1: the same restriction enzyme cuts the human gene and the plasmid, leaving complementary sticky ends that DNA ligase joins into a recombinant plasmid
Section 01
What genetic modification is.
Press Next step to work through how bacteria are made to produce human insulin, then use the GM crop chips (herbicide resistance, insect resistance, nutrition) to see the plant examples.
Definition: genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes.
Human proteins from bacteria: the human insulin gene is inserted into bacteria, which then make human insulin for people with diabetes.
Herbicide-resistant crops (such as soya and maize): the farmer can spray herbicide to kill the weeds without harming the crop.
Insect-resistant crops (such as maize): a gene from a bacterium makes the plant produce a toxin that kills insect pests that eat it, so less insecticide is sprayed.
Improved nutrition: for example golden rice, with genes added so the grains contain a substance the body converts to vitamin A.
Examiner trap
Genetic modification is not the same as selective breeding. Selective breeding mixes whole sets of genes over many generations; genetic modification moves or changes individual genes, often between different species.
Section 02
Cut, paste, multiply.
Extended. The seven steps in the sim follow the syllabus outline for making a human protein in bacteria. Step through them again and match each step to the list below.
Isolate the gene: the DNA making up the human gene is cut out using restriction enzymes, which cut at specific base sequences and leave short single-stranded sticky ends.
Cut the plasmid: a bacterial plasmid is cut with the same restriction enzymes, forming complementary sticky ends.
Join: the human DNA is inserted into the plasmid; the sticky ends pair up by complementary base pairing and DNA ligase joins the DNA backbones, forming a recombinant plasmid.
Insert: the recombinant plasmids are put into bacteria.
Multiply: the bacteria reproduce rapidly (for example in a fermenter), copying the recombinant plasmid each time.
Express: the bacteria use the human gene to make the human protein, such as insulin, which is extracted and purified.
Examiner trap
Restriction enzymes cut DNA; DNA ligase joins it. The same restriction enzyme must cut both the gene and the plasmid, or the sticky ends will not be complementary.
Stage 1 · Learn
Check what the sim just showed you
Four quick checks. Each correct answer earns XP and records this skill on your profile.
Quick check+10 XP
In the sim, what do the restriction enzymes do in step 2?
Quick check+10 XP
In the sim, which enzyme joins the human gene into the plasmid?
Quick check+10 XP
Which GM crop example in the sim lets a farmer spray weeds without harming the crop?
Quick check+10 XP
What happens in the last step of the sim?
Section 03
GM crops: for and against.
Extended. Choose the pros and cons chip in the sim. GM soya, maize and rice are grown widely, but people disagree about whether the benefits outweigh the risks.
Advantages
Disadvantages
higher yields: less crop lost to weeds and insect pests
GM seed is expensive and may have to be bought again every year
insect-resistant maize needs less insecticide spraying
insects that are not pests may be harmed; pests may evolve resistance to the toxin
herbicide-resistant soya and maize make weed control easier
herbicide use may increase; genes may spread to wild relatives, making herbicide-resistant weeds
golden rice could reduce vitamin A deficiency
large areas of one GM variety reduce biodiversity
crops can be made to grow in poor soils or drought
some people worry about long-term effects on health
Examiner trap
In a 'discuss' question give both sides: at least one advantage and one disadvantage, each linked to a named crop where you can (soya, maize, rice).
Stage 2 · Exam
Exam-style questions
Unlocks once the four checks above are done. Worth more XP, written to IGCSE Paper 2 and Paper 4 standard.
Finish the four checks above to unlock the exam questions
Exam style+20 XP
Which statement describes genetic modification?
Exam style+20 XP
Extended: why must the same restriction enzyme be used to cut the human DNA and the plasmid?
Exam style+20 XP
Extended: what is a recombinant plasmid?
Exam style+20 XP
Extended: which is a disadvantage of growing GM herbicide-resistant maize?
Skill unlocked
Genetic modification, mastered.
This skill is now recorded on your profile. Keep the chain going.