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Restriction enzyme

Enzymes produced by certain bacteria which cut DNA at specific sites. They are widely used in genetic engineering.

Type 1 diabetes

Develops when the body does not produce the right amount of insulin or, in some cases, does not produce any at all. It must be treated with daily injections of insulin. People affected also need to manage their diet, eat regularly and plan exercise carefully to balance their energy needs with their food and insulin intake.

Type 2 diabetes

The pancreas does produce insulin but cells stop responding properly to the insulin. It is often linked to obesity and lack of exercise and taking more exercise, losing weight and eating a carefully balanced diet can often control or even reverse type 2 diabetes.

Blood vessels

The tubes through which blood is carried around the body eg arteries, veins and capillaries


Energy producing organic compounds which are made of carbon, hydrogen and oxygen. Examples of food containing carbohydrate are rice, pasta, bread and potatoes

Blood sugar

The sugar (glucose) dissolved in the blood; the normal range is 4.0 - 7.8 mmol/l


A chromosome is like a packet of coiled up DNA. Humans have 23 pairs of chromosomes. They are in the nucleus of every human cell.


Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus


An endocrine gland which produces insulin


A polysaccharide, (C6H10O5)n, that is stored in the liver and in muscles and can be converted back into glucose when needed by the body.

Diabetes mellitus

A disease resulting from a lack of insulin production by the pancreas or a loss of the cell response to insulin that causes a loss of control of the glucose balance of the body.


A type of sugar: a mono saccharide with 6 carbon atoms (a hexose sugar).


A hormone produced by the pancreas. It allows cells in the body to take in and store glucose.


A large organ in the upper abdomen which manufactures, stores and breaks down substances as required by the body


The main organ of the central nervous system made up mainly of grey matter


A short piece of DNA which is responsible for the inheritance of a particular characteristic. It codes for the production of a specific protein. Genes occupy a fixed position, called a locus, on a particular DNA molecule.


Deoxyribonucleic acid. This is the molecule which contains the genetic code. It coils up tightly inside chromosomes. DNA is a double helix made from two strands which are joined together by pairs of bases.


A selection of donuts with multicoloured icing
Eating bread, pasta, donuts or other sugary food causes the glucose level in blood to rise

After eating carbohydrate foods e.g. bread, pasta, sugary foods, the level of glucose in the blood rises. Glucose is important to the cells of the body, particularly the brain, as an energy source. However, the level of glucose in the blood must be regulated so that it does not rise too high.

When the bloodstream contains glucose the pancreas is stimulated to produce the hormone insulin. Insulin causes glucose to be usable by the body cells and excess to be stored in the liver and muscles as glycogen. If the body later needs glucose and none is available in the blood, the liver can convert glycogen back into glucose.


When the amount of insulin is too little (or absent altogether), or the action of insulin in the body is ineffective, the disease diabetes (correctly known as Diabetes Mellitus) will result. It is not a curable disease but can be controlled so that most sufferers can lead a full and normal life. However, if blood sugar levels are not controlled the diabetic could suffer from high blood pressure, and their kidneys, nerves, retina and blood vessels may become damaged.

Type 1 Diabetes

A young woman injects insulin into her thigh
Insulin may have to be injected several times a day

Type 1 diabetes develops when the body does not produce the right amount of insulin or, in some cases, does not produce any at all. It usually develops fairly quickly in early childhood or adolescence and there are about 350,000 sufferers at present in the UK. A good diet is important but this type of diabetes must be treated with daily injections of insulin. Before the development of insulin as a medicine, type 1 diabetes was usually fatal.

Type 2 Diabetes

An elderly man smiling
Older people, particularly those who are overweight, may suffer from Type 2 diabetes

The kind of diabetes that develops in older people, typically over 40 and overweight, is known as type 2 diabetes. In type 2 diabetes the pancreas does produce insulin but cells become increasingly intolerant to the action of the insulin. There are more than 2 million sufferers of type 2 diabetes in the UK at present and the number seems to be growing. Losing weight and eating a controlled diet can sometimes control type 2 diabetes but, in some cases, oral drugs and injections may be needed.

Genetic Engineering Makes Insulin

At one time, insulin needed for diabetics was extracted from the pancreases of slaughtered pigs, cows and sheep. Nowadays demand for insulin is high and it is important to have a more reliable source. Scientists use a process called genetic engineering to ensure that there is enough insulin for all who need it. The insulin produced by genetic engineering is identical to human insulin which is an added advantage of this process.

  • Researchers found the part of a human chromosome that has the gene for making insulin.
  • They carefully cut out the gene using a restriction enzyme and put it into some bacterial DNA.
  • This DNA was put into a new bacterium.
  • The bacterium grew and multiplied to produce very large numbers of bacteria each with the insulin-making gene inside.
  • The large numbers of bacteria could make a large amount of insulin.

Question 5