When James Watson and Francis Crick deciphered the structure of DNA in 1953, their discovery answered a crucial question in biology: How is genetic information passed from parent to child?
However, their work also created puzzles. They and others have shown that every cell in an organism contains all of its genetic material. How, then, does an individual cell know which genes to use and when? And how does the information from DNA get to the cell’s protein-making mechanism?
The fundamental understanding of these questions came from three biologists at the Institut Pasteur in Paris – Dr FranÃ§ois Jacob, Jacques Monod and AndrÃ© Lwoff. They identified messenger RNA which, as the name suggests, carries the pattern of a protein from cellular DNA to the ribosome, where proteins are built. They also identified the complex system of regulatory genes that turn protein-producing genes on and off.
PHOTOS: Notable deaths in 2013
Their achievement ushered in the modern era of molecular biology. It also earned them the Nobel Prize for Medicine or Physiology in 1965, just five years after Watson and Crick received theirs.
Jacob died in Paris on Friday at the age of 92. His death was announced by the French government, but no details were released.
The inspiration for Jacob’s accomplishments came in the early 1950s, when he was working in Lwoff’s lab studying bacteriophages, viruses that infect only bacteria. They studied a bacteriophage, or phage, which infected the common bacteria Escherichia coli. They observed that the phage could infect bacterial cells and remain dormant in its genes until something triggered explosive replication that caused the cell to separate.
In similar experiments with male and female bacteria, they found that male DNA infected with a dormant phage could be transferred into a female cell, but not the other way around. They concluded that something in the cells suppressed the activity of phage genes.
This led Jacob and Monod to study E. coli who normally live on glucose sugar. But if the bacteria are starved of glucose and placed in a medium containing the more complicated lactose sugar, they suddenly start to produce three enzymes which: 1) bring lactose into the cell; 2) break it down into its constituents glucose and galactose; and 3) breaking down galactose into glucose.
Through an elegant series of experiments, the researchers have shown that the genes that serve as blueprints for these three enzymes are each accompanied by another gene called the operator. In this system, glucose acts as a repressor, binding to the operator and physically preventing the plane gene from being copied into messenger RNA.
In other words, when the gene is not needed, it is turned off.
But when lactose is present, it binds more strongly to the operator than glucose, repelling the latter and allowing the structural gene to be copied. The researchers called this system of two genes an “operon” and the specific lactose system the lactose or the lac operon. They submitted their findings to the Journal of Molecular Biology on Christmas Eve in 1960 and it was published the following year.
In a review of the journal Science, molecular biologist Gunther S. Stent called it “one of the landmarks in the literature on molecular biology.” Introducing the three biologists at the Nobel Prize-giving ceremony, Sven Gard of the Royal Caroline Institute proclaimed that French workers “have opened up a field of research which, in the truest sense of the word, can be called molecular biology”.
FranÃ§ois Jacob was born on June 17, 1920 in Nancy, France, the son of a merchant. He began studying medicine at the University of Paris with the intention of becoming a surgeon, but the war intervened after his first two years. At the age of 20 he caught one of the last ships in England, where he joined the Free French Forces.
With his two years of medical training, he was a medic in the Free French Armored Forces throughout North Africa. After the Allied invasion of Normandy in 1944, as his armored brigade approached Paris, Jacob was seriously injured in a German attack when he used his own body to protect his lieutenant. He spent seven months in a hospital, missing the big re-entry of the Free French forces into the city. Damage to his hand ended his hopes of becoming a surgeon.
For his service, he received the Companion of the Liberation, the country’s highest decoration during World War II for his bravery. He also received the Legion of Honor and the Croix de Guerre.
After graduating from medicine in 1947, he joined a company that was trying to make a French version of penicillin and helped develop a related antibiotic called tyrothrycine. In 1950, at the age of 30, he decided to take an interest in cell genetics and obtained a scholarship at the Institut Pasteur, obtaining his doctorate in science in 1954.
He then studied the mechanisms of cell division and the early development of the mouse embryo.
In addition to his extensive research work, he is the author of four books, including the 1988 autobiography âThe Statue Withinâ.
He married pianist Lysiane “Lise” Bloch in 1947, and they had four children. After his death, he married GeneviÃ¨ve Barrier in 1999. Information on the survivors was not available.