California researchers using a type of electron microscope and a computer that creates three-dimensional images were able to create a direct visual image of the DNA molecule, an accomplishment they say will enable scientists to speed up efforts to map the human genetic code.

The image collected by the microscope shows the double helix coil that is the molecule of DNA, or deoxyribonucleic acid, magnified one million times. A report on the study was published Friday in Science, the journal of the American Association for the Advancement of Science.Rod Balhorn, a biologist at the Lawrence Livermore National Laboratory, said Thursday the development is a major advance in the study of genetics because scientists for the first time will be able to actually see extremely small molecules that perform key functions in the cell.

"This is a major new tool that will enable us to actually visualize molecules and atoms, something that has not been possible before," he said in a telephone interview.

Balhorn said the image enables scientists to clearly see the major and minor grooves between strands of the helix coil and to pick out specific protein pairs within the helix. The DNA molecule is made up of paired proteins whose sequence determines the genetic traits of each cell.