A full page illustration (in miniature below) can be easily converted into an overhead transparency to assist students in grasping the scale of the genome mapping project.
“Mapping” the human genome is a huge task which involves determining the sequence of some 3 billion base pairs in a single cell. The number of base pairs of DNA can be thought of as roughly equal to the total number of people on earth. Thus, if a physical map could be drawn showing the identity and location of each living person on earth, this mapping feat would be comparable in scale to what molecular biologists hope to accomplish in the next 15 years with the genome.
Using the single
(50 to 250 million base pairs each) are analogous to countries, and genes (thousands to millions of base pairs) to
. Between chromosomes and genes in size are chromosome fragments (1-50 million bp) and on the comparative scale a
is analogous to a
(figure available in print form)
FIGURE LP-1: Comparative Scale of Genome Mapping
(Courtesy of U.S. Congress, Office of Technology Assessment.
Mapping Our Genes — The Genome Projects: How Big, How Fast?
If students can begin to grasp the scope of the genome project in these terms, they may understand why it will take so long and why emerging technologies for automatic sequencing of portions of DNA are so useful. Questions should be raised for further exploration and discussion: Is the genome project “big science” in the classic sense of the Manhattan Project and Moon Landing of previous decades or the Superconducting Supercollider of this decade? Is the genome project worth the estimated cost of 3 billion dollars? A little research will quickly uncover strong arguments for either side of this question and an interested group of students might enjoy staging a debate on this topic for the class.