Benjamin Stark (Biology Department, IIT)
Ben did these two miniteach presentations at this first class of the semester:
^ | Increasing | 2CH2 + 3O2 | Energy | | | | | | (heat and light released) | | | \ / | | 2H2O + 2 CO2 |Karlene Joseph [Lane Tech HS, Biology] then discussed how a very similar chemical reaction
... \\ || // ..... \\ || // ... \\ || // .. \\||// \\// Speckled StripedSuch speckled or striped kernels helped Barbara McClintock discover "mobile genetic elements" or "jumping genes". She received the Nobel Prize in Medicine in 1983 for this discovery. Each kernel is an individual embryo derived from a single cell. The genes in such a progenitor cell can be set to give one color. However, in a cell that is created after several cell divisions have occurred, a "jumping gene" can move and change the genetic makeup so as to change the color of that cell, and all cells subsequently derived from it. This leads to a patch (speckle or stripe) of cells of the new color on the background of cells with the original color. Here is a schematic to illustrate the process:
0: cells of original color X:: cells of new color due to movement of jumping gene ® Cell Divisions ® 0 ® 00 ® 00 ® 000 ® 000 ® 00000 ® ® ® ® ® "blob" 00 000 00000 000000 00X 00XXX 000000 XXXXXX original jumping speckled cell event regionSee the websites http://www.ndsu.nodak.edu/instruct/mcclean/plsc431/transelem/trans1.htm and http://www.profiles.nlm.nih.gov/LL/Views/Exhibit/narrative/nobel.html.
1902-1992 Barbara McClintock. Though American botanist
Barbara McClintock conducted the research that led to her discovery of
mobile genetic elements in the 940s, it was not until decades later that
scientists began to take her work seriously. McClintock experimented with
variation in the colors of corn kernels on a single cob. She tracked pigmentation
changes in the corn and observed through microscopic evidence that two
transposable genes called "controlling elements" were influencing the corn's
pigmentation according to where their ever-changing position was on the corn's
chromosomes. Whichever enes became the genetic neighbors of these controlling
elements in a given generation of corn accounted for the changes in pigmentation
McClintock observed. In 1983, McClintock became the first female recipient of
the Nobel Prize for Physiology or Medicine. Scientists today believe "jumping genes,"
or transposons, may be linked to some genetic disorders such as hemophilia, leukemia,
and breast cancer, and may have played critical roles in human evolution.
Notes provided by Ben Stark