Disease and Infection
This section is about how people in the past have tried to explain the causes of disease and infection
and how they have tried to prevent and to cure them.
(i) The Ancient World
The Prehistoric World
Evidence about the prehistoric period is limited but comes from two main sources:
‐ Archaeological finds, e.g. bones and the remains of tools and plants
‐ The culture of current peoples whose lives haven’t changed much since p rehistoric times,e.g. the aborigines of Australia
Based on this evidence, historians can draw some fairly reliable conclusions:
- Prehistoric people largely explained disease and infection through the spirits they believed in. A bad spirit could enter the body and cause an illness.
- In order to treat illness a patient might be given a herbal remedy by someone in their family.
- The patient could also go and see a medicine man who was a half‐priest, half‐doctor figure.The medicine man would put the patient into a trance, use herbal remedies, and chant spells and prayers to get the bad spirits to leave the body.
Therefore, prehistoric people had a supernatural approach to disease and infection.
Egyptians also had a supernatural approach to disease and infection. They had temples of healing
and several gods and goddesses to whom people prayed to get better. Sekhmet was a goddess who
could cause and cure epidemics and Imhotep was a god of healing. Other Egyptian sources mention
people going to see ‘priest‐magicians’ in search of cures.
Other supernatural ideas the Egyptians had to prevent or cure disease and infection were:
- Wearing magic charms to ward off evil spirits.
- Making ointments out of the fat of animals which they believed had healing powers, e.g.cats, crocodiles and snakes.
- Bathing in water that had been blessed by a priest.
- Swallowing mice whole was believed to cure certain conditions.
However, the Egyptians also developed a natural approach to disease and infection. They observed
the River Nile and how the irrigation channels from the river brought life to their fields. They
developed the theory that the body has channels through which blood, air and water flow. They
believed that you became ill when these channels were blocked. One cause of blocked channels
they thought of was rotting food. They believed that this is why you are sick when you are ill – your
body is trying to get rid of the rotten food. The rotten food could also cause other symptoms such as
wind and diarrhoea.
Other natural ideas the Egyptians had about how to prevent and cure disease and infection were:
- Herbal remedies – many Egyptian medicines contained honey which has been shown by modern science to have anti‐bacterial properties.
- Using mosquito nets to keep the insects off the body. The Egyptians had clearly realised that insects could spread diseases.
- Keeping the body clean and washing regularly.
- Making yourself or the patient sick – this was to get rid of the rotten food blocking thechannels.
Some of the Ancient Greeks had a supernatural approach to disease and infection. They believed
that illness was caused by the gods and that the only way to get better was to pray at an Asclepion
which was a temple built to worship Asclepius, the god of healing.
At an Asclepion they would:
- Make offerings to Asclepius and his two daughters – Panacea and Hygeia.
- Sleep in the abaton – a building next to the temple where they believed that Asclepius wouldvisit them in their sleep and cure their illness.
- Asclepions also had baths, gymnasiums and were built in the fresh air of the countryside.
These things would have helped people to recover as well, but they believed it was the
power of the god that was curing them.
Other Greeks rejected supernatural ideas and developed more natural approaches. They used herbal
remedies in the same way as the Egyptians had. The best known of the Greeks’ natural approaches is
the Theory of the Four Humours which was developed by Hippocrates.
This theory said:
- The body is made up of four liquids (humours) – blood, phlegm, black bile and yellow bile.
- If the humours are in balance then you are healthy, however, if there is too much of one
humour then you are ill.
The Theory of the Four Humours seemed to be a very good idea because:
- It explained the symptoms of many illnesses, for example in the winter when you get runny noses the theory said that you had too much phlegm. If you were sick, your body was trying to get rid of yellow bile. Diarrhoea was a symptom of having too much black bile.
- It fitted in with the Greeks’ beliefs about the four elements (earth, air, fire and water) and also the four seasons. Therefore winter was cold and wet, which was why you had too much phlegm in that season. Water which is also cold and wet was the dominant element in winter.
- It also fitted in with the Greeks’ belief in leading a balanced lifestyle. They thought that not eating or drinking too much would help to keep you healthy. Hippocrates is a very important figure in the history of medicine because:
- He developed the Theory of the Four Humours which was believed for the next 2000 years.
- He totally rejected any supernatural beliefs about disease and infection. He insisted that all illness had a natural cause and could only be treated with natural remedies. He said that doctors should carefully observe and record the symptoms of their patients.
- He came up with the Hippocratic Oath which set out how doctors should behave, e.g. they should never give patients anything which could harm them and they should keep their patients’ details totally confidential. These are still rules for doctors nowadays.
- He wrote many books about his ideas which were still being read 2000 years later.
Therefore, Hippocrates is important because he set out the methods which doctors use even in the
present day – careful observation and recording; rejecting supernatural beliefs; maintaining high
standards of professional behaviour. However, Hippocrates did not come up with many treatments to
cure diseases – he could recognise and name many illnesses but he couldn’t effectively cure any. The
most common treatment based on his ideas was bleeding, which was done to get rid of excess blood
in line with the Theory of the Four Humours.
The Romans had strong supernatural beliefs in the gods. As a result they also had temples of healing
and prayed to different gods to cure illnesses. Salus was a goddess of healing. The Romans even built
temples to Asclepius as they had heard of his supposed healing powers from the Greeks.
The Romans also had natural approaches to disease and infection. They used herbal remedies and
because their Empire stretched so far they were able to get hold of a wider range of natural
ingredients for their medicines. A Roman medical book lists 600 different herbal remedies.
Early on, the Romans were very suspicious of Greek doctors and their theories. The Romans liked to
think of themselves as practical people who did not get carried away with fancy ideas. Their attitude
towards Greek theories began to change with the arrival of Galen in Rome in AD 161. Galen is
- He was trained at Alexandria in the natural ideas of the Greeks including the importance of
careful observation and recording and the need to lead a healthy lifestyle.
- He introduced the Theory of the Four Humours to ancient Rome.
- He added his own Theory of Opposites which explained many more treatments that could be
offered based on the theory of the four humours, e.g. giving patients dried pepper to balance
out too much phlegm. Galen was enthusiastic about the use of bleeding as a treatment.
- He became the doctor to the Roman Emperor which allowed him to spread his ideas quickly.
- He wrote many books which eventually became the most important medical textbooks in
medieval Europe 1000 years later and were still being read in the Renaissance.
The Middle Ages and the Renaissance
The Dark Ages in Europe (500 – 1000 AD)
The Roman Empire collapsed around the year 500 AD. The period that followed is called the Dark Ages
because there is not that much information about it. During the Dark Ages the standard of medical
care and knowledge declined. People relied more heavily on supernatural approaches to medicine
and did not continue the Greek and Roman interest in finding out more about the human body. In the
Dark Ages, Europe was taken over by warlike tribes.
This led to a decline in medicine because:
- The rulers spent far more money on soldiers and weapons than on medical progress and universities.
- War disrupted the normal channels of communication which meant that medical ideas could not be shared as easily.
- Many books were destroyed or hidden during the Dark Ages, for example the books ofHippocrates and Galen.
As a result most people relied on prayer and religion to explain and cure illness. They would still have
used herbal remedies passed down through families but not a lot of other natural treatments.
The Islamic Empire (700 – 1450 AD)
Whilst Europe was in a period of decline during the Dark Ages, the Islamic Empire in the Middle East
was far more advanced and civilised. There was one strong ruler – the Caliph – who was able to invest
money in universities and hospitals because he did not have to spend as much of his money on war.
The best example of this is the new university and hospital built next to each other in Baghdad in
about 800 AD. At the same time a centre for the translation of Greek and Roman books was set up.
This centre translated the work of Hippocrates and Galen into Arabic.
The first great Islamic doctor was Al‐Razi.
Following the ideas of Hippocrates, he stressed
the importance of careful observation and
recording. Using this method he was able to
identify the difference between smallpox and
measles. He became the first director of the new
hospital in Baghdad. Al Razi was a great admirer
of Galen but he also prepared to criticise him
where he thought Galen was wrong.
Ibn Sina (Avicenna)
The second great Islamic doctor was Ibn Sina. He wrote a million‐word encyclopaedia called ‘The
Canon’. In it he summarised the whole of medical knowledge up to the year 1000, including
Hippocrates, Galen and Islamic doctors. Ibn Sina was an expert on drugs and he listed the properties
of 760 different drugs, some of which are still in use today, e.g. camphor and laudanum.
Islamic medicine was more advanced than European medicine during the Middle Ages. This was
something the Crusaders discovered when they invaded the Holy Land in the 11th and 12th centuries.
This was due to the continuation of Greek and Roman knowledge in the Islamic Empire which had
been lost in Europe. However, there were limitations on the advances of the Islamic Empire:
‐ Islamic beliefs prevented the dissection of human bodies
‐ Most Islamic doctors did not believe it was right to dabble in surgery
‐ The Islamic Empire suffered as much from the Black Death as medieval Europe did
The Middle Ages in Europe(1000 – 1450 AD)
The Middle Ages were dominated by the Church, which was the most powerful and wealthy
international organisation. The Church controlled all of the universities and therefore the training of
doctors. The Church helped medical progress in some ways but hindered its development in others.
The Church helped by:
‐ setting up universities where doctors could train, e.g. Salerno, Padua. After the Dark Ages, the books
of Galen and Hippocrates were slowly rediscovered and doctors could study these.
‐ running and paying for hospitals. These were often part of monasteries or cathedrals and offered
some medical care by the monks or nuns who had some skill with herbal remedies.
Banning dissections because it was believed that the whole body would be needed in the afterlife.
(This ban was relaxed a little in the 14th century when each university could do one dissection per year)
Encouraging people to believe that God caused diseases and to pray or go on pilgrimages to cure
illnesses. This meant that most people in the Middle Ages had a supernatural approach to illness.
The Church also hindered progress by:
Insisting that Galen was right about everything. The Church liked Galen because he said the
human body is like a perfectly interconnecting machine. This fitted in with their belief that God
had designed the human body. This attitude prevented doctors from challenging some of Galen’s
mistakes. If a body being dissected was different from Galen’s book, they said that the body was
wrong not Galen.
Doctors in the Middle Ages
Doctors in the Middle Ages had both natural and supernatural approaches to disease and infection.
Their natural approaches included:
- Following the Theory of the Four Humours and using treatments like bleeding based on the theory.
- Using herbal remedies
- Inspecting the urine of patients to diagnose their illnesses (although some doctors relied on this so much they didn’t actually bother to meet their patients)
Their supernatural approaches included:
- Consulting Zodiac charts to find out what was wrong with their patients.
The Black Death
In 1348, the Black Death struck western Europe. It had already swept across Asia and the Middle East
killing millions of people. The disease was the bubonic and pneumonic plagues which killed 90% of
people who caught within about five days. The people of medieval Europe were desperate to avoid
catching the plague and to cure it if they got it. They tried both natural and supernatural methods:
Their natural approaches included:
- Cleaning up streets because they believed that the bad smells (miasma) spread the disease
- Bleeding or purging (being sick) the body because the humours were out of balance
- Burning herbs to take away the bad smells (miasma)
- Blaming Jews for poisoning the water supply. Hundreds of Jewish people were murderedbecause of this belief during the Black Death outbreak.
Their supernatural approaches included:
- The belief that the plague was caused by the position of the planets
- Praying to God to take the plague away because he had sent it as a punishment for people’ssins. One group of people – the flagellants – whipped themselves as they walked through townsand villages to show God how sorry they were for sinning.
- Saying magic spells and wearing charms to keep the plague away
The Renaissance (1450 – 1700 AD)
The Renaissance was very different from the Middle Ages because the power of the Church was
reduced. This meant that the restrictions on dissecting bodies at universities were slowly lifted and that
doctors could now challenge Galen’s ideas openly. One good example of a Renaissance doctor is
Paracelsus, he is a good example because:
- He burned Galen’s books in public to show that he thought they were wrong. (It is important toremember that Galen got a lot of things right but he did make some mistakes)
- He chose his name because it means ‘Better than Celsus’. Celsus was a famous Roman doctorand Paraclesus believed that his new ideas were better than the old ones from Rome.
- He came up with new ideas of his own, e.g. that diseases should be treated with medicinesmade from chemicals. He used mercury in several of his medicines which is unfortunatelypoisonous.
- He gave lectures in German rather than Latin so everyone could understand them.
- However, Paracelsus’ influence was limited because he was regarded as a bit of an eccentric – some of his ideas were very supernatural. For example, he believed that God had sent messages about themedicinal qualities of plants through their shape.
Overall, the Renaissance was a period of significant advances in the understanding of anatomy (Vesalius and Harvey) but there wasn’t much progress in the understanding of the causes of disease or discovering effective cures. Supernatural approaches continued alongside natural ones. Most doctors continued to believe in the Theory of the Four Humours.
The Industrial Age (1750‐1900)
During the Renaissance and after, the training of doctors at universities increasingly focused on using a
scientific approach based on careful observation and recording of patients’ symptoms and on carrying
out experiments to test new ideas and theories. One doctor who used this scientific method to make
an important breakthrough was Edward Jenner.
Edward Jenner and Smallpox
Through his work as a doctor in a countryside area of Gloucestershire, Jenner came across several
famers who rejected the offer of being inoculated against smallpox, an horrific killer disease. They did
this because they believed they were already protected having suffered from the much milder illness,
cowpox. Jenner decided to test this idea out scientifically:
1. Jenner observed and took careful records of milkmaids who had suffered from cowpox. None of
those he examined had ever caught smallpox.
2. Jenner then decided to test his theory. An 8‐year‐old boy called James Phipps was given cowpox
by Jenner. After this disease had passed, Jenner then gave him a dose of smallpox but there was
no reaction – it appeared that the boy was now immune to smallpox.
3. Jenner tried this out a further 23 times and each time the patient did not develop smallpox.
Jenner called his discovery ‘vaccination’ after the Latin for cow – ‘vacca’. He published his findings but
immediately faced a lot of opposition.
People were concerned about vaccination because:
‐ Many people were uneasy about new ideas in general but especially one that involved giving
humans and animal disease.
‐ Jenner could not explain how vaccination worked which worried some people.
‐ Doctors who made a lot of money out of the old method of inoculation were against vaccination
because it would put them out of business.
‐ Vaccination was not totally safe and some doctors did not take as much care as Jenner. Their
patients’ cuts became infected or they went on to catch smallpox anyway.
Jenner was helped in overcoming this opposition by support from the government and other prominent
- Parliament granted him £30,000 to set up a vaccination clinic in London
- Thomas Jefferson, President of America, promoted vaccination in the USA.
- Napoleon had all of his soldiers vaccinated in 1805
In 1852, the British government made vaccinations compulsory. Some people resented being told what to do by the government and refused to be vaccinated, however, by 1900 smallpox had nearly died out in Britain as a result of Jenner’s work. Smallpox was eventually eradicated completely from the world in 1980 as a result of a mass vaccination programme organised by the World Health Organisation.
Louis Pasteur and Germ Theory
Since the 17th century scientists had used basic microscopes to observe tiny micro‐organisms invisible to
the naked eye. They had observed that there were more microbes on matter that was rotting and
wondered why. The most popular explanation for a long time was called spontaneous generation. This
theory said that as matter rotted or decayed it turned into the microbes. Therefore, they thought,
germs were the result of disease and decay.
Some scientists disagreed. They thought that germs were the cause of disease and decay. This idea was
called Germ Theory. One scientist who believed this was Louis Pasteur and he was able to prove it by:
- In the 1850s, He was asked by the French wine industry to investigate why their winesometimes went off. He observed through his microscope that there seemed to be a lot of the same germs in the wine that was off. He found that if you heated the wine the germs died and then it would stay fresh. He had shown that the germs were the cause of wine going bad.
- In 1864, He entered a competition to show that Germ Theory was correct and spontaneous generation was wrong. He took samples of air in two glass containers. He heated one container until the germs were dead and then sealed it – it stayed fresh. The other container was not heated and the germs began to grow in it until they were visible.
- In the second half of the 1860s, he was asked by the French silkworm industry to find out why some silkworms were dying. He observed that all of the dead silkworms seemed to have the same bacteria in them. He and his assistants then tested all the other silkworms and separated the ones with the germs from the healthy ones. The disease stopped spreading in the healthy silkworms. Pasteur had shown that the germs were the cause of the silkworm disease.
Pasteur suffered a stroke in the late 1860s which prevented him from following up his work. He had
shown that germs cause decay in liquids, and also disease in silkworms. The next step was to show that
germs could cause human diseases too.
Koch was the first scientist to identify a specific bacteria which caused a specific human disease. The
bacteria he identified was anthrax in 1878. He did this by:
- Extracting what he thought was the anthrax bacteria from a dead sheep.
- Injecting the bacteria into a mouse which then died of anthrax.
- Extracting the bacteria from the dead mouse and injecting it into another one.
- Repeating this process 20 times after which he still had the same bacteria which he started with.
- Koch had successfully identified the anthrax bacteria.
Robert Koch went on to identify the septicaemia bacteria later in 1878. Using his methods other
scientists also discovered typhus, tetanus, pneumonia, meningitis and plague. Koch also developed agar
jelly as a better medium for growing and observing bacteria. He also invented a way of staining
bacteria using chemical dyes and photographing them through a microscope.
Louis Pasteur vs Robert Koch
Pasteur and Koch became great rivals. France and Germany had recently been at war and there was still ill‐feeling between them. The French and German governments gave Pasteur and Koch large sums of money and created huge research teams for them in order to make the next breakthrough and claim the glory for their country. Pasteur came out of retirement to try to surpass Koch’s achievements:
1879 ‐ Pasteur discovered how vaccinations work. One of his assistants had left a petri dish of chicken
cholera out over the summer holidays. When they came back to the lab, Pasteur injected a
chicken with these germs but it did not die. When they injected the same chicken with a fresh
batch of cholera it still did not die. Pasteur made the connection that maybe the chicken had
been accidentally vaccinated by the weakened form of the disease which had been left out.
1881 ‐ Pasteur now understood how vaccinations work – a weakened form of a disease allows the
body’s immune system to learn how to fight off the infection. He developed a new vaccine for
anthrax and demonstrated it in public. He vaccinated 25 sheep and left another 25 alone. Two
weeks later he gave all 50 sheep a deadly dose of anthrax. The 25 vaccinated sheep survived
and the 25 others died. This experiment made front page news all over the world.
1882 ‐ Koch identified the tuberculosis bacteria
1883 ‐ Koch identified the cholera bacteria
1886 ‐ Pasteur tried out a new vaccine for rabies successfully. He had spent four years developing the
new vaccine which was very difficult because the rabies bacteria is very small. A boy who had
been bitten by a rabid dog was brought to him. The boy was certain to die, so Pasteur tried out
his vaccine – it worked because the disease was not yet full‐blown in the boy. This also became
famous around the world.
By 1900, therefore, scientists had discovered the true cause of disease – a massive breakthrough. They
also now understood how vaccines worked and had produced several new ones. However, no‐one had
yet invented a cure for a disease that had already taken effect in a person’s body.
Improvements to Nursing
Florence Nightingale was from a rich family and was not expected to work but due to her strong
religious beliefs she was determined to work as a nurse and improve hospital care. Her opportunity
came during the Crimean War (1854‐56) when she persuaded a contact of her family in the
government to allow her to travel to the Crimea with a team of nurses.
Nightingale struggled to get the Army doctors to let her implement her ideas but she was a very strong and persuasive personality. Eventually she introduced changes which reduced the death rate in the military hospital from 42% to 2%. She achieved this through:
- Introducing wards for soldiers with similar diseases, which reduced cross‐infection
- Insisting on high standards of cleanliness (Nightingale did not know about Germ Theory yet)
- Keeping careful records of medicines given and patients’ progress
- Installing beds for all patients
- Providing 24 hour care (hence the nickname ‘Lady with the Lamp’)
Nightingale became a national heroine for her work in the Crimea but she was determined that this
should be the start rather than the end of her work. On returning to Britain she transformed the
nursing profession from a very low‐status and unskilled job to a highly respected and professional
occupation. She did this by:
1. Writing a book on nursing which became a best‐seller
2. Setting up a training school for nurses which insisted on the highest standards
3. Advising new hospitals on how to set out their buildings
Mary Seacole was the daughter of a Scottish army officer and a Jamaican woman. She had some
knowledge and skill at nursing and wanted to help out in the Crimea just like Florence Nightingale. In
the Crimea, she set up a ‘British Hotel’ which offered medical care and a shop for troops. She was
rejected as a nurse by Florence Nightingale due to the colour of her skin. Mary Seacole was also
celebrated after the war for her work with injured soldiers and was given a medal for her service.
However, a few years later she was largely forgotten and she did not have the huge impact which
Nightingale had back in Britain. Reasons for this are:
- She was black and society in Victorian Britain was racist
- She was not from a rich and well‐connected family like Nightingale
The stories of Nightingale and Seacole are a good example of the factor of war in the history of
medicine as well as the influence of other factors such as race and wealth on the impact an individual
1900 to the Present Day
The First Cures
Paul Ehrlich and Salvarsan 606
Ehrlich had been a member of Robert Koch’s research team. He had used the method of staining
bacteria to observe them more easily. He thought that he could find a chemical which both stained
bacteria but also killed them. If it could kill the bacteria then this would be the first cure. He nicknamed
this idea ‘magic bullets’ because the chemical would seek out the bacteria and kill them without
harming anything else.
Ehrlich and his team painstakingly tested hundreds of different chemicals on syphilis bacteria (a sexually
transmitted infection). In 1909, Ehrlich became convinced that chemicals based on arsenic would be the
most effective. The 606th arsenic compound which they tested seemed to work. Even then they only
spotted it when they were double checking every test. They called the chemical Salvarsan 606.
This was the first ever cure – a very important breakthrough BUT Salvarsan 606 only worked on the
syphilis bacteria and not on any other diseases. Also, because it was derived from arsenic it proved to
be too dangerous to be used widely as a drug. When the First World War broke out more money was
invested in other types of medicine especially surgery and Ehrlich’s work was not developed for a while.
Gerhardt Domagk and Prontosil
In the 1920s and 30s, another German scientist – Gerhardt Domagk – decided to try to find another
chemical cure like Ehrlich had. In 1932, he tested the chemical dye, Prontosil, on mice and found that it
had an effect on the bacteria which caused blood poisoning.
One day, Domagk’s daughter cut herself by accident in his lab and developed a severe case of blood
poisoning. She was likely to die, so Domagk decided to try out Prontosil on her. It worked. He had
found the second cure.
In the 1930s, a new electron microscope had been invented. This allowed scientists to analyse
chemicals like Prontosil to discover what the active ingredients were. They discovered that the active
ingredient in Prontosil was a sulphonamide. Sulphonamides are found in coal tar. It turned out that
there are lots of different types of sulphonamides and that some of them were useful in curing other
diseases. Drugs companies invested huge amounts of money into researching sulphonamides and soon
cures existed for scarlet fever, meningitis, gonorrhoea and pneumonia.
The Development of Penicillin
1928 ‐ Alexander Fleming was a British scientist researching bacteria in the 1920s. One day in 1928 he
was tidying up his lab and noticed that in one petri dish there was a circle where the bacteria
had been killed. When he looked closer he found that a spore of penicillin had got into the dish
and had killed the bacteria. He thought the penicillin must have blown in through the window.
1929 ‐ Fleming published a research paper about his discovery of penicillin but he lacked the funding to
continue his research any further. It was very difficult to grow and harvest enough penicillin to
make a useful drug.
1937 ‐ Two scientists working at Oxford University – Howard Florey and Ernst Chain – read Flemings
paper on penicillin and decided to try to develop it as a drug.
1939 ‐ With the outbreak of the Second World War, the British government was prepared to put more
money into research for drugs which could save soldiers’ lives. Florey and Chain were given
money to develop penicillin. They did this by:
- Using new freeze‐drying technology and some milk bottles to grow and harvest some
- Testing the small amount they had harvested on eight mice. All the mice were given deadly
microbes. Four mice were then given penicillin and survived, the other four mice died.
1941 ‐ By now Florey and Chain had just about enough penicillin to test it on a human patient. One
patient in the hospital was seriously ill with an infected head wound. They gave the man
penicillin and his condition improved. They had so little of the drug that they even recycled the
penicillin which passed out of the patient in his urine. The man was getting better but they ran
out of penicillin and he died, however, they had proved that it worked on humans.
1942 ‐ The USA entered the war and also wanted a drug which would save soldiers’ lives. Florey and
Chain moved to America where they were safe from German air‐raids, but also where there
were huge drugs companies with the money and technology to develop mass‐production of
penicillin. The American government provided $80 million for this.
1944 ‐ By the time of D‐Day in June 1944 there was enough penicillin to treat all of the wounded Allied
soldiers in France.
1945 ‐ By the end of the war the US Army was using 2 million doses of penicillin a month. It is
estimated that another 15% of wounded Allied soldiers would have died without penicillin.
The Fight Against Disease and Infection since 1945
The Discovery of DNA
In 1953, Francis Crick and James Watson, discovered the ‘double‐helix’ structure of DNA. They also
discovered how DNA can ‘un‐zip’ and make copies of itself. They were able to do this using the latest xray
photography technology developed by Maurice Wilkins. Since 1953, scientists have gained more
and more understanding of how DNA holds the genetic code to the human body. This has led to some
very important developments in medicine, for example:
- A gene which is damaged by liver cancer has been discovered. The drug Oltipraz has been shown to protect this gene from the disease and stop people from developing cancer. This has been particularly important in China where many people suffer from liver cancer due to a mould which grows on rice.
- Genetic screening of parents and babies can lead to early identification of hereditary diseases which can now be treated much earlier, giving the child a better chance of survival.
- Genetic screening of embryos can allow the birth of ‘saviour siblings’ who are born as a perfect genetic match to an older brother or sister who has a serious illness. Stem cells from the younger sibling can be used in the treatment of their older brother or sister.
Genetic engineering is a controversial subject and there are several objections raised by different groups
in the modern world:
‐ Religious groups are concerned that genetic engineering is messing with God’s creation.
‐ Other people worry about the unknown long‐term side effects of tampering with the DNA of
plants, animals and humans. For example, there are worries about the impact of genetically
modified crops on the environment.
‐ The cost of developing drugs based on genetic information is a problem.
The Development of New Drugs
Since the Second World War there has been an explosion in the development of new drugs. Large drugs
companies invest huge amounts of money into developing new medicines. Most of these new drugs are
very effective at curing diseases. However, there have been problems:
‐ A few drugs have had very bad side effects. The most famous is the drug Thalidomide which
was given to pregnant women to ease morning sickness in the 1950s. Unfortunately, many of
the babies these women gave birth to had seriously deformed arms and legs.
‐ The cost of new drugs is a problem for the NHS but also for poorer countries in the Third World.
This means that many people struggle to get hold of drugs which could save their lives.
‐ The over‐use of antibiotics has led to the evolution of ‘superbugs’ such as MRSA which are
resistant to modern drugs.