What We Have Learned In June 2000, scientists announced that a working copy of the human genome was complete. The first details appeared in the February 2001 issues of the journals Nature and Science. The full reference sequence was completed in April 2003, marking the end of the Human Genome Project—two years ahead of the original schedule. Coincidentally, that was also the fiftieth anniversary of Watson and Crick's publication of DNA structure that launched the era of molecular biology!

FIGURE 14–14 Announcements The first details of the human genome appeared in two well-known scientific journals in February 2001.

Besides finding that the human genome in its haploid form contains three billion nucleotide bases, the Human Genome Project uncovered a wealth of interesting, and sometimes surprising, information. For instance, only about 2 percent of our genome encodes instructions for the synthesis of proteins, and many chromosomes contain large areas with very few genes. As much as half of our genome is made up of DNA sequences from viruses and other genetic elements within human chromosomes. During the project, investigators completed the genomes of several other organisms, including unicellular ones. They found that more than 40 percent of the proteins coded for by our genome have strong similarity to proteins in many of those organisms, including fruit flies, worms, and even yeast. Figure 14–15 compares the human genome with these and other model organisms.

By any standard, the Human Genome Project has been a great scientific success. The Human Genome Project pinpointed genes and associated particular sequences in those genes with numerous diseases and disorders. It also identified about three million locations where single-base DNA differences occur in humans. This information may help us find DNA sequences associated with diabetes, cancer, and other health problems. The Human Genome Project also transferred important new technologies to the private sector, including agriculture and medicine. By doing so, the project catalyzed the U.S. biotechnology industry and fostered the development of new medical applications.

FIGURE 14–15 Genome Size Comparisons The gene numbers in this table are not final. Some estimates include only protein-coding genes, while others include genes that code only for RNA. The discovery of small interfering RNAs (siRNAs) has complicated the definition of a gene. Propose a Solution How could you find updated information on genome sizes?

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