Evolution and inheritance, Year 11: genetic engineering

Genetic engineering

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

为什么Genes 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

提示It is the hormone that a healthy pancreas releases.

为什么The 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

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

为什么A 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

提示Think of the plants in the hedgerow and the animals that visit them.

为什么This 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

提示The word for how much food a field produces.

为什么Crops 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

提示They are the same kind of molecule that speeds up digestion.

为什么The 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

提示In Year 10 the same word described the mosquito that carries malaria.

为什么The 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

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

为什么A 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

提示All later cells grow from those first few.

为什么An 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

提示It needs a carrier before it can enter the target cells.

为什么There 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.