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Genetic engineering

Genetic engineering involves changing the DNA of an organism, usually by deleting, inserting or editing a gene to produce desired characteristics.

Cystic fibrosis

A genetic disease caused by a defective, recessive gene. It is characterised by the production of thick, sticky mucous in the lungs and pancreas which cause respiratory and digestive problems.


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.

Stem cell

Cells which can divide repeatedly without becoming differentiated and have the capacity to develop into a diverse range of specialised cell types.


The umbrella name given to a number of cancers of the bone marrow and other organs which produce white blood cells.


The science of genes, heredity and variation.


Bases, sometimes called nitrogenous bases, are the parts of the DNA molecule that join the two helix strands. They are like rungs on a ladder. There are four bases: adenine (A), thymine (T), guanine (G) and cytosine (C). Each base can only join with one other base; i.e. they join together in pairs: A with T and G with C.


A viral infection of the breathing system which attacks the lungs and can be fatal

2000 and beyond: 21st century medicine

Pharmaceutical companies around the world have driven a decade of advances in medicines
(PhRMA Biopharmaceuticals in Perspective, 2016)

It is impossible to say how medicine will develop over the rest of the century but undoubtedly our knowledge of genetics will be of great importance.

Human genome project

The double helix of DNA
Watson and Crick built their model of DNA using templates like this one to show how the molecules in DNA were arranged

The task was to find the sequence of DNA for every single gene in a complete set of human chromosomes. We call this sequence the human genome. It started in 1990 and saw unprecedented scientific collaboration between research laboratories in the United States, Europe, Asia and Australia. Using highly automated analytical techniques, the task was completed in 2003, which was barely 50 years after Watson and Crick first described the double helix structure of DNA.

Some surprising discoveries were made. The instructions for an entire human is held in only about 20,500 different genes and all but a few percent of these are common to our nearest relatives, the chimpanzees. There is still much more to be done to understand what each of these different genes do.

Genetics and medicine

Human chromosomes stained with a fluorescent dye. The sequence of bases A, G, C and T hold the genetic information
(Wellcome Images)

The risk of developing many disorders, such as Alzheimer's, diabetes and heart disease, may well be influenced by our genetic make-up. Greater understanding of the human genome will direct the development of medicines to help treat and prevent diseases, as well as helping to identify those treatments that could work best for patients based on their genetic make-up. Advances in genetics will allow treatments to target the genes or specific proteins that cause disease. Gene therapies are being developed that aim to replace faulty genes and so reverse the effects of inherited disorders such as cystic fibrosis.

Ethics and medicine

Advances in medical science will not come without challenges.

  • Technology has made genetic fingerprinting a routine task but how should this information be used?
  • Individuals can be warned of diseases that they are likely to develop in older age but this profile could also be used to assess a person's suitability for insurance or employment. How can we protect the rights of the individual?
  • Genetic engineering and stem cell therapies may provide cures for diseases such as cancer, leukaemia and Parkinson's but are these experiments ethical or not?
  • Will the benefits outweigh the risks?
  • The emotional burden of a person being told of a potential risk of developing a disease and its consequences.

Throughout the ages, medicine has been influenced by the spiritual and superstitious beliefs of the day. Knowledge built up over the centuries has led to modern treatments that are based on a molecular understanding of how the body works. The ethical and moral concerns of modern society will continue to shape the development of new medicines and treatments.

New challenges

It is impossible to prevent all diseases. Bacteria are evolving resistance to antibiotics and viruses evolve resulting in infections such outbreaks of swine flu in 2009-10, ebola in 2013 and zika virus in 2015-16.

As life expectancy rises, fresh challenges will emerge in the treatment of the elderly. One issue that medicine alone cannot tackle is to raise the living conditions of people throughout the world so that they do not suffer from diseases of poverty. As always, modern medicine will continue to face fresh challenges and find new solutions for the 21st Century.

The video below, ‘Only Just Begun’ summarises the history of the UK pharmaceutical industry in changing the lives of patients, and celebrates the people involved in its past, present and future.


The table shows some imaginary situations in which it might be appropriate to use information about a person's genetic profile. In each case, decide whether you think it is right and click on the button.

Imaginary situation
not sure
a) There is a history of genetic illness in the family but it does not show up until the person is an adult. Should a genetic test be done to see if the person has the disorder or not?
b) A gene that makes smokers more likely to get lung cancer has been discovered. Should all smokers be able to get a genetic test to see if they have the gene?
c) A couple are considering in-vitro fertilisation. They ask for genetic tests be done on any embryos before they are implanted in the woman's uterus to make sure that they are going to have healthy children?