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Fact # 2) The Most Common Sequences in Our Genomes Have a Surprising Source.

• To a first approximation, most of our genes are NOT our own. In fact, only about 2% of the human genome seems to be made up of sequences that code for proteins or RNA. What about the remaining 98% of it? Well, fully half of it consists of highly repreated DNA sequences of the sort shown below:

A copy of this Figure is available from NATURE magazine at:
http://www.nature.com/nature/journal/v409/n6822/fig_tab/409860a0_F17.html

• Guess where these sequences come from? Ultimately, most of them come from viruses. In fact, there are so many copies of viral genes scattered around our DNA that the single most common protein sequence in our genome is the "recipe" for making Reverse Transcriptase (the "pol" sequence in the figure above). Reverse Transcriptase is an enzyme used by retroviruses to copy their genes into our own DNA. In a sense, you could say that most of our DNA actually comes from viruses. That might not be pleasant to think of, but it seems to be the case.

For More Information, visit the ORNL Genome Information Site:

http://www.ornl.gov/hgmis/project/journals/insights.html

 

The Human Genome Top Ten: 10 9 8 7 6 5 4 3 2 1

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(A web site developed by Ken Miller and Joe Levine to provide scientific and education support for teachers and students using our textbooks)