Cornflakes have more genes than people do
ON JUNE 26, 2000 two geneticists, Craig Venter and Francis Collins, triumphantly announced that the research teams they headed had completed the first survey of the three billion base pairs of DNA that make up the human genome.
As Mukherjee’s sweeping history of genetics shows, this was an achievement that deserved all the praise lavished on it.
If the human genome were published as a book with a standard size font, it would run to more than a million and a half pages — 66 times the size of Encyclopaedia Britannica — and contain just four letters (AGCT) which refer to the four bases found in DNA.
It encodes about 20,700 genes, only 1,700 more than worms and 25,000 fewer than rice or wheat. Humblingly, our breakfast cereal has more genes than we do, but thankfully it’s not the numbers that are important but the sophistication of the gene networks.
The discovery of the gene was the work of an Augustinian friar in mid-19th-century Brno, now in the Czech Republic, named Gregor Mendel.
Earlier thinkers had wondered about human heredity: the Ancient Greek philosopher Pythagoras believed all the information was carried in the sperm, and medieval and Renaissance alchemists envisaged little mini-humans curled up within it. Some of the first users of the microscope even claimed to have spotted these under their lenses.
Such ideas had long been dismissed by Mendel’s day, but no satisfactory theory of heredity had replaced them. In his abbey, Mendel began to experiment. He wanted to use mice, but his abbot objected. So Mendel turned to peas instead.
He crossed tall peas with short peas, wrinkled ones with smooth, green ones with yellow.
As generation succeeded generation, Mendel began to detect a pattern. He realised there were corpuscles of hereditary information moving from one generation to the next — he’d discovered the essential features of the gene.
He published his findings — which were ignored by the scientific world. Between 1866 and 1900 Mendel’s paper was cited only four times.
Tantalisingly, Darwin nearly heard about it. In the early 1870s he read a book on plant hybrids and made extensive notes on pages 50, 51, 53 and 54. For some reason he skipped page 52, on which Mendel’s peas were discussed. As it was, it was left to English biologist William Bateson to rediscover Mendel’s work in 1900, coin the word ‘genetics’ and initiate the great strides the science took in the 20th century.
Mukherjee describes the path from Mendel to the Human Genome Project and beyond with energy and panache. His story of Francis Crick and James Watson’s unravelling of the structure of DNA is concise and illuminating.
Aware of the perils of genetics, he calls his book ‘the story of the birth, growth, and future of one of the most powerful and dangerous ideas in the history of science’ and he pays due attention to its misuse in Nazi eugenics.
This is a brilliantly readable celebration of the science and scientists who have transformed our understanding of what it means to be human.