DNA: what it all means

What is DNA?

All life on earth, from daffodils to blue whales, owes its form and substance to the genetic information carried within DNA. DNA is the most important molecule in the living world, the chemical messenger bearing the message of heredity down the generations. The letters stand for deoxyribonucleic acid.

Can you actually see DNA and what does it look like?

Although DNA is the longest molecule, you cannot see it with the naked eye. Scientists have recently taken blurred photographs of it with extremely powerful microscopes. Its double helix is just about visible. If all the DNA could be pulled out of each cell and unfurled it would be about two metres long. Human DNA contains enough information to fill 1,000 paperback books.

Who discovered it?

The German biochemist Friedrich Miescher in 1869; he found it in pus cells taken from discarded bandages. For the next 75 years, scientists thought DNA was a boring molecule. Then in 1945, Oswald Avery at the Rockefeller Institute in New York showed that DNA carried genetic material from one cell to another. Even then, biochemists found it hard to believe that DNA was interesting and Avery never won the Nobel Prize he merited.

Watson and Crick discovered the structure of DNA, from which scientists understood for the first time how genes are passed on. The discovery opened up a new and immensely powerful scientific discipline, now known as molecular biology.

So what is the structure?

DNA consists of two long chains entwined in the form of a double helix. The message of inheritance is written along the double helix, in the form of chemicals known as 'base pairs' which join the two strands rather like the steps of a spiral staircase. When a living cell divides to form two 'daughter cells', the double helix unzips and the base pairs separate, so that the two separate helices can carry genetic information to the 'daughter' cells. This was the insight denied to all previous scientists.

How was the double helix found?

Watson and Crick had access to X-ray pictures of DNA fibres taken by Maurice Wilkins and Rosalind Franklin at King's College London. The pictures were formidably difficult to interpret and personal antagonismbetween Wilkins and Franklin was hindering their research. Rather than working it out by sophisticated mathematical analysis as Franklin was trying to do, Watson and Crick decided it would be quicker to try building scale models of the molecule until they got a structure consistent with the X-ray data. It was a matter of inspired guesswork rather than logical deduction.

What does it mean for Darwinism and evolution?

Discovering the structure of DNA was the final vindication of Darwinism. The idea that living creatures were descended from common ancestors arose initially from observations of the anatomical similarity of their bodies. Analysis of DNA has since demonstrated this similarity at the level of genetic anatomy. For example, a human being's DNA differs from that of a chimpanzee by only about 2 per cent.

Can you recreate dinosaurs with it?

The idea that it is possible to recreate extinct animals from their preserved DNA is a myth. Scientists have been able to isolate preserved DNA from very old organisms, such as a termite 30 million years old fossilised in amber. But such DNA is only partially preserved, and the small fractions that can be analysed could only be used to gauge how evolution has changed the molecule over that period of time.

Have there been any practical uses of the discovery?

The technology of manipulating, splicing and amplifying DNA has spawned a multi-billion-pound biotechnology industry producing everthing from pharmaceutical products and non-squashy tomotoes to washing powders. Medicine is about to experience one of its greatest revolutions as a result. Doctors are now able to diagnose an increasing number of genetic diseases. Transplanting healthy genes into children with genetic disorders is under way. DNA fingerprinting, used by the police to identify murderers and rapists, was made possible by it.

Does every living thing contain DNA?

The only known lifeform not to have DNA is a group of viruses that use a close molecular cousin, RNA, to carry genetic instructions. The Aids virus, for instance, is an RNA virus. Like DNA, RNA can replicate itself with the help of certain enzymes. Some biologists believe that RNA evolved before DNA but it is probably too unstable to have been able to allow even organisms as simple as bacteria to exist and was supplanted by the more stable DNA.

Was it a Faustian discovery?

Crick's autobiography says:'The double helix is indeed a remarkable molecule. Modern man is perhaps 50,000 years old, civilisation has existed for scarcely 10,000 years, the United States for only just over 200; but DNA and RNA have been around for at least several billion years. All that time, the double helix has been there, and active, and yet we are the first creatures on Earth to become aware of its existence.'

The knowledge is one of the pinnacles of achievement of our civilisation. But all knowledge can be used for good or for ill. Developments stemming from Watson's and Crick's discovery have given humanity the power to alter its own genetic composition. Is this a power with which we can be trusted?

Sport
Premier League Live
footballLIVE Follow all the Premier League action as it happens
News
The slice of Prince Charles and Princess Diana's wedding cake and the original box from 29 July 1981
newsPiece of Charles and Diana's wedding cake sold at auction in US
Life and Style
3D printed bump keys can access almost any lock
gadgets + echSoftware needs photo of lock and not much more
News
James Argent from Towie is missing, police say
peopleTV star had been reported missing
PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
News
ebooksAn evocation of the conflict through the eyes of those who lived through it
Arts and Entertainment
Gregg Wallace in Summer's Supermarket Secrets
tv All of this year's 15 contestants have now been named
News
i100(and it's got nothing to do with the Great British Bake Off)
Arts and Entertainment
Inside the gallery at Frederick Bremer School in Walthamstow
tvSimon Usborne goes behind the scenes to watch the latest series
Life and Style
A picture taken on January 12, 2011 shows sex shops at the Paris district of Pigalle.
newsThe industry's trade body issued the moratorium on Friday
Arts and Entertainment
Could we see Iain back in the Bake Off tent next week?
tv Contestant teased Newsnight viewers on potential reappearance
Life and Style
Silvia says of her famous creation: 'I never stopped wearing it. Because I like to wear things when they are off the radar'
fashionThe fashion house celebrated fifteen years of the punchy pouch with a weighty tome
News
i100
Voices
The Ukip leader has consistently refused to be drawn on where he would mount an attempt to secure a parliamentary seat
voicesNigel Farage: Those who predicted we would lose momentum heading into the 2015 election are going to have to think again
Arts and Entertainment
Cara Delevingne made her acting debut in Anna Karenina in 2012
film Cara Delevingne 'in talks' to star in Zoolander sequel
Sport
Mario Balotelli pictured in his Liverpool shirt for the first time
football
News
i100
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Clinical Negligence Solicitor

Highly Competitive Salary: Austen Lloyd: HAMPSHIRE MARKET TOWN - A highly attr...

Network Engineer (CCNP, CCNA, Linux, OSPF, BGP, Multicast, WAN)

£35000 per annum: Harrington Starr: Network Engineer (CCNP, CCNA, Linux, OSPF,...

Commercial Property Solicitor - Bristol

Highly Attractive Package: Austen Lloyd: A VERY HIGH QUALITY FIRM A high qual...

DevOps Engineer (Systems Administration, Linux, Shell, Bash)

£50000 per annum: Harrington Starr: DevOps Engineer (Systems Administration, L...

Day In a Page

Ukraine crisis: The phoney war is over as Russian troops and armour pour across the border

The phoney war is over

Russian troops and armour pour into Ukraine
Potatoes could be off the menu as crop pests threaten UK

Potatoes could be off the menu as crop pests threaten UK

The world’s entire food system is under attack - and Britain is most at risk, according to a new study
Gangnam smile: why the Chinese are flocking to South Korea to buy a new face

Gangnam smile: why the Chinese are flocking to South Korea to buy a new face

Seoul's plastic surgery industry is booming thanks to the popularity of the K-Pop look
From Mozart to Orson Welles: Creative geniuses who peaked too soon

Creative geniuses who peaked too soon

After the death of Sandy Wilson, 90, who wrote his only hit musical in his twenties, John Walsh wonders what it's like to peak too soon and go on to live a life more ordinary
Caught in the crossfire of a cyber Cold War

Caught in the crossfire of a cyber Cold War

Fears are mounting that Vladimir Putin has instructed hackers to target banks like JP Morgan
Salomé's feminine wiles have inspired writers, painters and musicians for 2,000 years

Salomé: A head for seduction

Salomé's feminine wiles have inspired writers, painters and musicians for 2,000 years. Now audiences can meet the Biblical femme fatale in two new stage and screen projects
From Bram Stoker to Stanley Kubrick, the British Library's latest exhibition celebrates all things Gothic

British Library celebrates all things Gothic

Forthcoming exhibition Terror and Wonder: The Gothic Imagination will be the UK's largest ever celebration of Gothic literature
The Hard Rock Café's owners are embroiled in a bitter legal dispute - but is the restaurant chain worth fighting for?

Is the Hard Rock Café worth fighting for?

The restaurant chain's owners are currently embroiled in a bitter legal dispute
Caribbean cuisine is becoming increasingly popular in the UK ... and there's more to it than jerk chicken at carnival

In search of Caribbean soul food

Caribbean cuisine is becoming increasingly popular in the UK ... and there's more to it than jerk chicken at carnival
11 best face powders

11 best face powders

Sweep away shiny skin with our pick of the best pressed and loose powder bases
England vs Norway: Roy Hodgson's hands tied by exploding top flight

Roy Hodgson's hands tied by exploding top flight

Lack of Englishmen at leading Premier League clubs leaves manager hamstrung
Angel Di Maria and Cristiano Ronaldo: A tale of two Manchester United No 7s

Di Maria and Ronaldo: A tale of two Manchester United No 7s

They both inherited the iconic shirt at Old Trafford, but the £59.7m new boy is joining a club in a very different state
Israel-Gaza conflict: No victory for Israel despite weeks of death and devastation

Robert Fisk: No victory for Israel despite weeks of devastation

Palestinians have won: they are still in Gaza, and Hamas is still there
Mary Beard writes character reference for Twitter troll who called her a 'slut'

Unlikely friends: Mary Beard and the troll who called her a ‘filthy old slut’

The Cambridge University classicist even wrote the student a character reference
America’s new apartheid: Prosperous white districts are choosing to break away from black cities and go it alone

America’s new apartheid

Prosperous white districts are choosing to break away from black cities and go it alone