Farnham, Peggy J. Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California.
- What has been learned from ENCODE?
- About 60% of the genome is transcribed into some form of RNA
- About 95% of the genome lies within 8 kilobases of a protein--DNA interaction
- The genome has a highly complex interactive structure
- Insights into human health
- Further exploration
- Links to Primary Literature
- Additional Readings
Many human diseases are caused by changes in the abundance or activity of proteins, and proteins are encoded by segments of DNA called genes. Therefore, a logical assumption is that identifying all the human genes could help in understanding human disease. The Human Genome Project was launched in 1990 with this specific goal in mind. This led to a push for sequencing the entire genome, which began in 1996, with a draft version of the human genome being published in 2001. One of the first big surprises that came from this era of human genomics had to do with the number of genes that was found. Based on the fact that genomic sequencing of a worm (which has only 959 cells and 1 × 108 nucleotides of DNA) had identified approximately 20,000 genes, it was assumed that humans would have approximately 150,000 genes (after all, a human is much more complicated than a worm). However, after the human genome was sequenced and “read” by computational programs that compared the results to known proteins and RNAs (the intermediary nucleic acids from which proteins are encoded), the results suggested that humans might have at most 30,000 genes; refinement of the analyses has since reduced this number to 20,000. In other words, a human has the same number of genes as a worm. In fact, only 5% of the 3 × 109 nucleotides in the human genome is covered by exons (DNA segments that encode proteins). This realization led to an intriguing question: If 95% of the genome is not involved in coding for proteins, then what does it do? A large international consortium called ENCODE (Encyclopedia of DNA Elements), funded by the National Human Genome Research Institute, began to address this question in 2004, and a pilot project was undertaken to study 1% of the human genome. However, ENCODE quickly advanced to studying the entire genome by 2007 because of technological improvements. The assays chosen by the ENCODE consortium focused on identifying regions of the genome that are “in use”—for example, regions that are transcribed into RNA or regions that control whether a gene is turned on or off. Since 2007, 442 scientists from 32 different institutes have studied 147 cell types and collected more than 1640 data sets; these efforts from the ENCODE consortium have shed light on several important questions in human biology.
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information