caption: Detailed chromosome descriptions, together with other biological resources, software, and instrumentation generated in the first seven years of the DOE Human Genome Program (HGP), are enabling researchers to begin focusing on their most challenging goal: Determining the sequence of DNA subunits (the bases A, T, C, G) found in the 24 different human chromosomes. Differences in DNA sequence underlie much of life's diversity.

The image depicts the progress of human genome research, beginning with a microscopic view of a duplicated chromosome (left). Genome researchers begin with a very small chromosomal fragment (asterisk), using enzymes to cut it into the smaller pieces (red bars) required for DNA sequencing. Automated technology determines the DNA sequence of all or part of each fragment (graph with color-coded peaks).

Another HGP goal is to identify the estimated 30,000 genes, which account for only about 5 percent of human DNA. Computer analysis of DNA sequences is one way investigators identify gene features in DNA sequences (solid line with tick marks). In a living cell, individual gene segments from DNA molecules are assembled into short-lived intermediary molecules (short red line), and the information is translated by the cell's machinery into three-dimensional proteins (black globular structure at right). All organisms are made up largely of proteins that provide the structural components and specialized enzymes required by cells and tissues.

Public resources and technologies arising from the HGP and other genome efforts worldwide are laying the foundation for future explorations into the functions of each protein encoded by the genes. This research, which also will investigate how proteins work together in systems and pathways and react to external cues, will extend far into the future.

For more on the science behind the Human Genome Project, see our Genetics 101 Website.

This image originally appeared on the cover of the 1997 DOE Human Genome Program Report.