High School Biology-Chemistry SMILE Meeting
11 September 2001
Notes Prepared by Porter Johnson


Ben Stark (IIT)
Ben showed a copy of the human genome. He then explained how they cut up the base sequence of the chromosomes into pieces small enough to sequence. Bases that comprise the DNA sequence are  A, C, T, and G molecules, each gene corresponding to a different sequence. A computer was used to find gene sequences within the overall DNA sequence of the genome.

A primary feature of the genome is that there are places at which there are many genes, and some regions at which there are very few. There are thought to be about 35,000 genes in the human genome.

Some bacteria have up to 7000 genes, so it was expected that humans would have more than 35,000 genes.

The federally funded sequencing effort first ordered DNA pieces and then sequenced them.  The privately funded effort done by Celera Genomics Corporation http://www.celera.com/ sequenced randomly generated pieces, using a computer to order them by finding overlapping components.

The genome will be refined by comparing the federally funded and privately funded maps, and rectifying any differences. Then the problem of filling in missing genes (if any), will be addressed.

He then talked about butterflies, and the cells that make up all living things. All cells in any organism have exactly the same chromosomes with exactly the same genes.  The genes in all the cells are not active at the same time, so this is why certain butterflies develop wings with, say, black and orange colored patterns. This is analogous to a series of hotel rooms that all have the same number of lights, each with a different combination of bulbs turned "on" and "off".

Harmful bacteria can have their genomes sequenced within a few weeks. The smallest known bacterial genome, that of an obligate  intracellular parasite, has about 450 genes. 

Next he looked at a DNA model to see the bases on the inside and the outer parts. An actual DNA molecule is 19 = 1.9 nanometers [nm] in diameter, but the diameter of the model is 0.19 meters.  Thus, the model is larger than the actual molecule by a factor of 100,000,000; or 108.

Notes taken by Therese Donatello