Evolution and inheritance, Year 11: genetic engineering

Genetic engineering

HintThe second word is also the job of someone who designs bridges.

The whyGenes from the chromosomes of humans and other organisms can be cut out and transferred to the cells of other organisms. Crops changed in this way are called genetically modified, or GM, crops.

Human insulin

HintIt is the hormone that a healthy pancreas releases.

The whyThe human gene for insulin is transferred into bacteria. The bacteria reproduce quickly and make the hormone, which is then collected and purified for people with diabetes.

insect; herbicides

HintOne is an animal pest; the other is a chemical sprayed on weeds.

The whyA crop that resists insect attack loses less to pests. A crop that resists a herbicide survives when the field is sprayed to kill weeds. Both are reasons why GM crops generally show increased yields.

They may affect populations of wild flowers and insects

HintThink of the plants in the hedgerow and the animals that visit them.

The whyThis is one of two concerns named at GCSE. The other is that some people feel the effects of eating GM crops on human health have not been fully explored. In an exam you weigh such concerns against the benefits, using the information given.

yield

HintThe word for how much food a field produces.

The whyCrops have been engineered to resist diseases, insects or herbicides, or to produce bigger and better fruits. Less of the crop is lost, so more food is harvested from the same land. This is the main benefit claimed for GM crops in agriculture.

Enzymes

HintThey are the same kind of molecule that speeds up digestion.

The whyThe first step is to isolate the required gene from the rest of the DNA, and enzymes do this. The isolated gene is then inserted into a vector.

A vector

HintIn Year 10 the same word described the mosquito that carries malaria.

The whyThe isolated gene is inserted into a vector, and the vector is then used to insert the gene into the required cells. The vector is usually a bacterial plasmid or a virus.

plasmid; virus

HintOne is a small ring of DNA; the other is a pathogen that enters cells.

The whyA plasmid is a small ring of DNA found in bacterial cells, separate from the main loop. Both plasmids and viruses can carry a piece of DNA into a cell, which is what makes them useful as vectors.

So that it develops with the desired characteristic

HintAll later cells grow from those first few.

The whyAn organism starts as very few cells, and every later cell is copied from them by mitosis. A gene added at that early stage is copied into the cells that follow, so the whole organism develops with the characteristic.

It is inserted into a vector

HintIt needs a carrier before it can enter the target cells.

The whyThere are three main steps, and the order matters. First, enzymes isolate the required gene. Second, the gene is inserted into a vector. Third, the vector inserts the gene into the required cells, at an early stage in their development.