Corn  

 
Group3~Honors Biology~Fall 2006
The University of Arizona
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CONCLUSIONS

There are two arguments to the theory about the domestication of maize.  One theory is from Mangelsdorf and Reeves stating that the teosinte could not be the ancestor of maize.  This was because the differences between maize and teosinte are so great that it would have taken thousands of years to evolve.  So, they argue that it had evolved in nature over a great length of time.  The second theory is argued by Beadle.  He challenged Mangelsdorf and Reeves stating that even the slightest change in a gene can cause a significant difference in the plant. 

In the experiment involving tga1, it was confirmed that the simple mutations in genes can cause a major change in the plant's phenotype.  The change in this gene could result in the soft casing of the maize, or could be the hard casing of the teosinte.  Thus, this paper proves the second theory, that the teosinte can be the ancestor of the maize.  The tga1 gene is expressed in the ear, but not elsewhere in the maize.   So it will not affect any other part of the plant.  This is the only genetic difference between the maize and the teosinte.

If the maize evolved from the teosinte it would have literally been turned inside out and it is more than ten times the size.  The teosinte has about ten kernels and each is surrounded by a hard casing.  The typical ear of corn has about 800 kernels.  Each kernel is held in place by a glume, and each ear is protected by a soft casing.  This makes the corn most accessible for food.  Humans unintentionally domesticated the maize plant through artificial selection.  This is so because corn has been widely used for nutritional purposes, therefore it was chosen over the teosinte because of the accessibility.  Because this is so, it was replanted more often and in large numbers and it was domesticated.