Genetic engineering

Genetic engineering is also called genetic modification (or GM). It is not the same as cloning [cloning: The production of genetically identical copies. ]. Although cloning techniques are used in genetic engineering, the two things should not be confused.

The table shows some of the differences.

How it works

Certain enzymes [enzymes: proteins which catalyse or speed up chemical reactions inside our bodies ] can cut pieces of DNA [DNA: The material inside the nucleus of cells, carrying genetic information. DNA stands for Deoxyribonucleic Acid. ] containing a particular gene from one organism, and join them into a gap in the DNA of another organism. This means that the new organism with the inserted genes has the genetic information for one or more new characteristics. For example, the organism might produce a useful substance, or be able to carry out a new function. We say that the organism has been genetically modified.

The animation shows how the method can be used to produce bacteria [bacteria: Single-celled micro-organisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium. ] that produce insulin. This is a human hormone [hormone: chemical messengers produced in glands and carried by the blood to specific organs in the body ] and valuable to people with diabetes [diabetes: a serious disease in which the body is unable to regulate blood sugar ]. Bacteria reproduce quickly, so a lot of insulin can be made quickly.

Problems

There are strong arguments for and against cloning and genetic engineering. It is possible to produce genetically modified animals and plants. Sheep that produce human proteins for treating the symptoms of cystic fibrosis (a disease which causes sufferers to produce abnormally thick and sticky mucus [mucus: Slimy white protein, which lines the respiratory tract and alimentary canal. ] in their lungs, leading to many health problems) have been produced, and even tobacco plants that glow in the dark when they need watering. Some people are excited by the almost limitless possibilities, while some people believe the process is unethical and should be banned. Others are concerned about what might happen in the future.

Selective breeding

Natural selection

Species [species: Used in the classification of living organisms, referring to related organisms capable of interbreeding. ] gradually evolve by a process of natural selection. The individuals in any population with the inherited features best suited to the environment in which they live are most likely to survive and reproduce. When they do, they pass on the genetic information for these features to their offspring [offspring: A new human, animal or plant that is created as a result of reproduction. ].

Over time, a species can change its appearance and may even become a new species, unable to reproduce successfully with individuals of the original species.

Artificial selection

Selective breeding, also called artificial selection, involves people taking charge of selection to produce new 'varieties' of various species. A variety is a type of a particular species that is different in some clear way from other varieties of that species.

For example, pedigree dogs come in lots of different varieties (or breeds) - they may be different colours and sizes, but they are all still dogs.

From left to right - Beagle, Wheaten Terrier, Rhodesian Ridgeback, Red Siberian Husky, Irish Setter, Golden Retriever, Boxer, Sheltie

Suppose you wanted a variety of cow that produced a lot of milk. This is what you could do:

• choose or select the cows in your herd that produce the most milk
• only let these cows reproduce
• select the offspring that produce the most milk
• only let these offspring reproduce
• keep repeating the process of selection and breeding until you achieve your goal

The key here is to identify the feature you want, and only breed from the individuals that have that feature. Here are some examples of what selective breeding can produce:

• hens that lay big eggs of a particular colour
• cattle that produce lots of meat
• tomato plants that produce lots of tomatoes
• crops that are resistant to certain plant diseases

Changing the characteristics of a species

The characteristics of a species can be changed by:

• natural selection
• selective breeding
• genetic engineering.

The table shows some differences between these.

In selective breeding and genetic engineering, there is a goal or desired outcome. For example, we may wish to produce a variety of cow capable of producing a lot of milk, or a bacterium capable of producing insulin [insulin: A hormone that regulates the level of sugar in the blood. It is produced in the Islets of Langerhans, in the Pancreas. ].

There is no goal in natural selection: although we find that particular species are well adapted to their environments, natural selection does not 'know' what the species should be like. Individuals that are better suited to their environment are more likely to survive to reproduce, and so pass on their characteristics to the next generation, than those that are poorly suited.

Classification

You will remember from your Key Stage 3 studies that species with similar characteristics are put into groups, and that this is called classification. Remind yourself of the basics of classification by looking here.

Kingdoms

The first rank in this system is called a kingdom. There are five kingdoms, based upon what an organism's cells are like:

1. animals (all multicellular animals)
2. plants (all green plants)
3. fungi (moulds, mushrooms, yeast)
4. prokaryotes (bacteria, blue-green algae)
5. protoctists (Amoeba, Paramecium)

Further divisions

There are several further ranks before we reach a particular species. In order, these are:

• kingdom
• phylum
• class
• order
• family
• genus
• species

For example, lions have the following classification:

• kingdom - animal
• phylum - vertebrate
• class - mammal
• order - carniverous
• family - cat
• genus - big cat
• species - lion

One way to remember this is by using a daft sentence like this one:

"Kevin plays clarinet or flute – grotty sound!"

Difficulties with classification

It can be easy to classify a species. For example, we are Homo sapiens.

Classification of species

It can also be difficult to classify a certain organism. For example, the single-celled organism called Euglena has some confusing characteristics. It has:

• chloroplasts, like a plant
• no cell wall, like an animal
• a flagellum to swim with, like some bacteria

A fifth kingdom, called the protoctists, was made for organisms like Euglena.

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