The work is important for medicine, because disturbances in that process are involved in illnesses like cancer, heart disease and various kinds of inflammation. And learning more about the process is key to using stem cells to treat disease.
Kornberg, 59, a professor at the Stanford University School of Medicine, had just spent two days traveling from Europe to his home in California when he learned of the honor.
"When the telephone first rang I was completely bewildered," he said in a telephone interview with journalists in the Swedish capital. "I'm still shaking. I hope I will be able to calm down shortly."
Kornberg said it wasn't his work alone that won the prize.
"I can accept this remarkable award on behalf of more than 50 coworkers who have done the work that is cited," he said. "This Nobel Prize, I think, is testimony to their extraordinary hard work and capabilities."
Kornberg's father, Arthur, shared the 1959 Nobel medicine prize with Severo Ochoa for studies of how genetic information is transferred from one DNA molecule to another.
The younger Kornberg said he remembered traveling to Stockholm with his father for the Nobel Prize award ceremonies.
"I have always been an admirer of his work and that of many others preceding me. I view them as truly giants of the last 50 years. It's hard to count myself among them," he said. "Something so remarkable as this can never be expected even though I was aware of the possibility. I couldn't conceivably have imagined that it would become reality."
The Kornbergs are the sixth father and son to both win Nobel Prizes. One father and daughter — Pierre Curie and IrGene Joliot-Curie — won Nobel Prizes in physics and chemistry, respectively. Marie Curie — IrGene's mother and Pierre's wife — won two Nobel prizes, for chemistry and physics.
Roger Kornberg's prize-winning work produced a detailed picture of transcription in eukaryotes, the group of organisms that includes humans and other mammals, the Royal Swedish Academy of Sciences said in its citation.
Kornberg shed light on how information is taken from genes and converted to molecules called messenger RNA. These molecules shuttle the information to the cells' protein-making machinery. Proteins, in turn, serve as building blocks and workhorses of the cell, vital to its structure and functions.
Since 2000, Kornberg has produced actual pictures of messenger RNA molecules being created, a process that resembles building a chain link by link. The images are so detailed that individual atoms can be distinguished.
"In an ingenious manner Kornberg has managed to freeze the construction process of RNA half-way through," the Nobel committee said. That let him capture the process of transcription in full flow, which is "truly revolutionary," the committee said.
Kornberg's team spent 10 years fine-tuning its lab procedures before they could be used to investigate transcription. "Many research groups would have given up much earlier, since several years went by without any actual results that could be published," the Nobel committee said.
Kornberg is the the fifth American to win a Nobel prize this year. So far, all the prizes — medicine, physics and chemistry — have gone to Americans.
Last year's Nobel laureates in chemistry were France's Yves Chauvin and Americans Robert H. Grubbs and Richard R. Schrock, who were honored for discoveries that let industry develop drugs and plastics more efficiently and with less hazardous waste.
Alfred Nobel, the wealthy Swedish industrialist and inventor of dynamite who endowed the prizes, left only vague guidelines for the selection committee.
In his will, he said the prize should be given to those who "shall have conferred the greatest benefit on mankind" and "have made the most important chemical discovery or improvement."
This year's Nobel announcements began Monday, with the Nobel Prize in medicine going to Americans Andrew Z. Fire and Craig C. Mello for discovering a powerful way to turn off the effect of specific genes, opening a potential new avenue for fighting diseases as diverse as cancer and AIDS. Their work dealt with how messenger RNA can be prevented from delivering its message to the protein-making machinery.
On Tuesday, Americans John C. Mather and George F. Smoot won the physics prize for work that helped cement the big-bang theory of how the universe was created and deepen understanding of the origin of galaxies and stars.
Each prize includes a check for $1.4 million, a diploma and a medal, which will be awarded by Sweden's King Carl XVI Gustaf at a ceremony in Stockholm on Dec. 10.