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Unit Chapters
The Human Genome Project
Sequencing a Genome
Finding Genes
Is the Eukaryotic Genome a Vast Junkyard?
The Difference May Lie Not in the Sequence but in the Expression
Determining Gene Function from Sequence Information
The Virtues of Knockouts
Genetic Variation Within Species and SNPs
Identifying and Using SNPs
Practical Applications of Genomics
Examining Gene Expression
Proteins & Proteomics
Evolution & Phylogenetics
Microbial Diversity
Emerging Infectious Diseases
Genetics of Development
Cell Biology & Cancer
Human Evolution
Biology of Sex & Gender
Genetically Modified Organisms
The Human Genome Project

" ...the acquisition of the sequence is only the beginning. The sequence information provides a starting point from which the real research into the thousands of diseases that have a genetic basis can begin."
- J. Craig Venter 1

In 1986 Nobel laureate Renato Dulbecco laid down the gauntlet to the scientific community to sequence the complete human genome. "Its significance," he said, "would be comparable to that of the effort that led to the conquest of space, and it should be carried out with the same spirit." 2 Dulbecco also argued that such a project should be "an international undertaking, because the sequence of the human DNA is the reality of the species, and everything that happens in the world depends upon those sequences."

Like the conquest of space, sequencing the human genome required the development of wholly new technologies. The human genome, containing more than three billion nucleotides, is vast. In 1986 DNA sequencing had yet to be automated and, consequently, was slow and tedious. Moreover, computer software for sequence analysis was just being developed. Similar to the Apollo project that met President Kennedy's goal of a manned lunar landing by 1970, the genome project also succeeded — beyond the dreams of the scientists who proposed it.

During the 1990s rapid progress was made in developing automated sequencing methods and improving computer hardware and software. By 2003 biologists had sequenced genomes from about one hundred different species. These species included dozens of bacteria and other microbes, as well as the model systems: yeast, fruit fly, nematode, and mouse. The capstone, of course, was the completion of the human genome sequence. In 2001 two rival teams jointly announced the completion of a draft sequence of the entire human genome, consisting of more than three billion nucleotides.

Is human DNA "the reality of the species"? Do we now have all the information we need to define human life? Perhaps surprisingly, the answers are no. Genetics is more than just DNA. While DNA is the blueprint for life, proteins carry out most cellular functions; DNA just codes for RNA, which codes for protein.

One major surprise emerged from the sequencing of the human genome. Although some scientists expected to find at least 100,000 genes coding for proteins, only about 30,000-35,000 of such genes appear to be in the human genome. These genes comprise only about two percent of the entire DNA. What is the rest of the DNA doing? Biologists once thought that this noncoding DNA was just junk, and hence called it "junk DNA." As we will see below, evidence now suggests that some junk DNA may have functions.

The quest to understand the workings of human cells will not be over until we understand how this genetic blueprint is used to produce a particular set of proteins - the proteome - for each type of cell and how these proteins control the physiology of the cell. (See the Proteins and Proteomics unit.) We should think of the human genome as a database of critical information that serves as a tool for exploring the workings of the cell and, ultimately, understanding how a complex living organism functions.

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