Genetic modification and GM crops

Last time

Before we start: last time, in Enzymes in biotechnology and fermenters, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Moving a gene

Insulin used to come from pigs. Now bacteria make human insulin for us. Scientists took a human gene and put it into a bacterium. That is genetic modification. Today: how it is done, step by step, then the crops it has produced, and the arguments for and against.

What it is

Genetic modification, or genetic engineering, is changing the genetic material of an organism by removing, changing or inserting individual genes. An organism with a gene from another species is called a transgenic, or GM, organism. It works across species because the genetic code is the same in nearly all living things.

The tools

Restriction enzymes cut DNA at specific sequences, so they can cut out a gene and also cut open a plasmid. DNA ligase joins pieces of DNA together, making a recombinant plasmid with the gene in it. The plasmid is a vector: it carries the gene into the bacterium.

Making human insulin

Stage one: cut out the human insulin gene using a restriction enzyme. Stage two: cut open a bacterial plasmid with the same enzyme. Stage three: join the gene into the plasmid with DNA ligase, forming a recombinant plasmid. Stage four: put the plasmid into bacteria. Stage five: grow the bacteria in a fermenter. They multiply and make insulin. Finally, the insulin is separated and purified for use by people with diabetes.

Why this is better

Human insulin from bacteria is identical to our own, so there are fewer side effects. Large amounts can be made quickly and cheaply, and there are no ethical concerns about using animals. The supply does not depend on the number of animals slaughtered.

GM crops

Insect-resistant crops contain a gene from a bacterium that makes a protein poisonous to certain insects. Herbicide-resistant crops survive spraying, while the weeds are killed. Golden rice has genes to make beta-carotene for vitamin A. Other GM crops tolerate drought, or give a higher yield, or stay fresh longer.

Advantages of GM crops

Higher yields and less pesticide used, so lower costs and less pollution. Crops with extra vitamins can reduce deficiency diseases, and crops that tolerate drought can grow in harsh places. These could help feed a growing population.

Concerns

The new gene might spread to wild plants by cross-pollination, for example herbicide resistance spreading to weeds. There may be harm to other organisms, such as insects that are not pests, and unknown effects on human health. GM seeds are more expensive, and farmers may depend on a few companies.