The Function of Genes
Year of Discovery: 1934
What Is It? Beadle discovered how genes perform their vital function.
Who Discovered It? George Beadle
Why Is This One of the 100 Greatest?
Genes are strung along chromosomes and contain directions for the operation and
growth of individual cells. But how can a molecule of nucleic acid (a gene) direct an entire
complex cell to perform in a certain way? George Beadle answered this critical question and
vastly improved our understanding of evolutionary genetics.
Beadle discovered that each gene directs the formation of a particular enzyme. Enzymes then swing the cell into action. His discovery filled a huge gap in scientists’ understanding of how DNA blueprints are translated into physical cell-building action. Beadle’s
groundbreaking work shifted the focus of the entire field of genetics research from the qualitative study of outward characteristics (what physical deformities are created by mutated
genes) to the quantitative chemical study of genes and their mode of producing enzymes.
How Was It Discovered?
George Beadle was supposed to be a farmer. He was born on a farm outside Wahoo,
Nebraska, in 1903. But a college study of the genetics of hybrid wheat hooked Beadle on the
wonder of genetics. Genetics instantly became his lifelong passion.
In 1937, at the age of 34, Beadle landed an appointment with the genetics faculty at
Stanford University. Stanford wanted to develop their study of biochemical genetics. The
study of genetics was 80 years old. But biochemical genetics, or the molecular study of how
genetics signals were created and sent to cells, was still in its infancy. Beadle teamed with
microbiologist Edward Tatum to try to determine how genes exercise their controlling
influence.
In concept their work was simple. In practice it was painstakingly tedious and demanding. They searched for the simplest life form they could find, choosing the bread mold
Neurospora because its simple gene structure had been well documented. They grew trays
upon trays of colonies of Neurospora in a common growth medium. Then Beadle and
Tatum bombarded every colony with X-rays, which were known to accelerate genetic mutations. Within 12 hours most colonies continued to grow normally (they were unmutated),
a few died (X-rays had destroyed them), and a precious few lived but failed to thrive (gene
mutations now made them unable to grow).
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