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Feature: 50 years of DNA discovery
Fifty years ago, Man took the first step in what would be an exhilarating but angst-tinged trek into the unknown, a journey of discovery into life itself.
Just as political turmoil can be triggered by apparently minor events, so the biological revolution which buffets our lives today began with a whimper.
On April 25, 1953, Britain’s Francis Crick and James Watson of the United States published in the British journal Nature their model of the structure of deoxyribonucleic acid (DNA), an intriguing molecule found in the nucleus of cells.
They described a double helix, joined together by rungs comprising pairs of four chemicals, and humbly suggested it could be the means for copying genetic material.
The implication was stunning: DNA was nothing less than the inherited template for creating and sustaining life.
It took several years for the community to understand that DNA’s strand has stretches, called genes, that are the inherited codes for making proteins, the building blocks of life.
Then, to make some practical use of this knowledge, scientists had to work out how the helix unzips to replicate itself during cell division and to create proteins, the substance which living things are mostly made up of.
Today, we are in the throes of a change likely to place the iron and silicon revolutions in the shade. If the early 21st century requires an icon, it is a twisted ladder.
In the past decade, the biotech tide has swept into almost every corner of the human experience.
It includes DNA forensic tests to clear up paternity cases and tools to diagnose inherited diseases. Research into new medicines or lab-grown transplant organs to halt or reverse those ailments. Novel crops which include genes spliced from other species. There are early DNA computers, which uses the ladder’s rung pairings as living chips to crunch data. And there is the lure of “nano” technology tools on a molecular scale.
But the genetic era is also more far-reaching than previous technical revolutions.
For it touches on the core questions of human identity: Who are we? Where did we come from? Is it our genes which determines who we are? Or is it the way we are brought up?
Knowledge of DNA has already prompted rogue scientists to attempt to clone humans, something laden with dangers for the child but also reeking with the stench of Nazi eugenics.
As for the time-worn Nature vs. Nurture debate, the pendulum has clearly swung away from social influence and back towards one’s genetic legacy as the big factor in shaping human nature.
But, says British science author Matt Ridley, we should not be afraid by the power of our genes.
“If freedom is what we prefer, then it is preferable to be determined by forces that originate in ourselves and not in others... Everybody has a unique and different, endogenous nature. A self.”
Richard Ingham Source: AFP
Genetic research: A historical timeline
1869: Swiss scientist Friedrich Miescher discovered that the nuclei of pus cells contain an acidic substance, which he named “nuclein.” He later found that nuclein comprises a protein and a sugar and phosphate compound to which the name nucleic acid — subsequently changed to deoxyribonucleic acid (DNA) — was given.
1928: Pneumonia vaccine researcher Frederick Griffith of Britain found that bacteria have a substance that causes heritable changes. He calls the phenomenon “transformation.”
1944: Canadian-US scientist Oswald Avery and others established that the substance causing Griffith’s “transformation” was DNA and suggested DNA may carry genetic information.
1949: Austrian-born US biochemist Erwin Chargaff gained insights into the pairing of four chemicals (adenine, thymine, cytosine and guanine) that make up the base composition of DNA.
1951-52: Groundbreaking technical work by British biologist Rosalind Franklin who took X-ray images of DNA.
1953: The double helix structure of DNA was described by Francis Crick of Britain and James Watson of the United States. They and another British scientist, X-ray imager Maurice Wilkins, won the 1962 Nobel Prize for Medicine for their work.
1955-61: Further work in Britain and the United States established DNA’s role in making proteins and how the molecule self-replicates and laid the foundation for gene sequencing.
1972: Dawn of genetic engineering with the creation of first recombinant DNA molecules.
1976: Genentech, the world’s first gene-engineering company was found.
1981: Scientists at Ohio University produced the first transgenic animals by transferring genes from other animals into mice. Three research teams discovered human cancer genes.
1982: First gene-engineered drug (human insulin) developed
1984: DNA fingerprinting was developed. Huntington’s disease pinned to gene on Chromosome 4.
1986: First genetically-engineered crops (tobacco plants) were authorized for release.
1990: First gene therapy performed successfully on a four-year-old American girl suffering from an immune disorder.
1994: First breast cancer gene was discovered.
1996: Birth of Dolly the Sheep, the world’s first cloned mammal. Discovery of first gene associated with Parkinson’s disease.
1998: Discovery that embryonic stem cells can be used to regenerate tissue.
2000: Publication of rough draft of the human genome. Other organisms whose genetic code had been sequenced include the mouse, the fruitfly, rice and bacteria and viruses including HIV, anthrax and the plague.
2001: First gene linked to language found.
2002: Claims, so far unsubstantiated, by alien-worshipping sect called the Raelians to have created the first cloned humans.
2003: Completed draft of the human genome published.
DNA: A genetic glossary
DNA: Deoxyribonucleic acid, the molecule that is the hereditary template for creating, repairing and ending life, whether human, plant or animal. Located in the nucleus of each cell, DNA comprises a long chain of phosphate and sugar in the shape of a double-helix ladder. The ladder’s two sides are connected by rung-like compounds, called bases, that are paired together.
GENES: Sections in the DNA chain that determine the synthesis of proteins, which govern all the life processes. The term gene derives from the Greek word “genos,” for birth or origin.
CHROMOSOME: A thread of DNA which comprises genes and sections of repetitive DNA that, so far as is known, do not have a purpose. Humans have 23 pairs of chromosomes and around 30,000 genes.
PROTEINS: Substances controlled by genes that make up virtually all of the body’s ingredients and are also responsible for switching genes on and off.
SEQUENCING: Describing the series of DNA base pairs in order to unravel the genetic code. There are four bases, each denoted by the letters A, C, G and T (for adenine, cytosine, guanine and thymine). They form around three billion base pairs in the human genome.
GENOME: The name for the genetic code that is derived from sequencing.
CLONE: A duplicate of an adult organism. In mammals, clones are created by removing the nucleus of an egg, replacing this core with DNA from the donor and fusing the egg and new nucleus together. Several barnyard species have been cloned this way, starting with Dolly the Sheep in 1996. But for reasons that remain obscure, many clones suffer from crippling health problems or, like Dolly, die prematurely.
GENETIC MEDICINE: Malfunctioning genes have been linked with a thousand disorders, ranging from heart disease, diabetes and asthma to cancer, obesity and Alzheimer’s. Doctors hope to use the human genome to devise medicines that block the working of a flawed gene, thus causing a disease to be stopped or reversed.
GENE THERAPY: An experimental approach in which a baulky gene is replaced with a correct one, delivered into cells by a disabled virus. The treatment is mired in controversy after the death of a young US volunteer with a liver disorder and after two French babies, treated for a severe disorder of the immune system, fell sick with leukemia. This has shown how much is still to be learnt about how genes interact and the importance of slotting the replacement gene at the right spot in the chromosome.
GENETICALLY MODIFIED ORGANISMS (GMOs): Plants that have had a gene inserted to them to alter their characteristics. A corn commonly grown in America, for instance, has a gene that causes it to exude a natural toxin that kills insect pests, thus offering the farmer savings in chemical insecticides. Farm animals and fish are among the next generation of GMOs. Critics say GMOs are potentially dangerous for health and the environment, but there is scant evidence, at this early stage, to support those claims.
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