Molecular Development and The Arthropod Head Problem
The study of how developmental genes are expressed during embryogenesis has become an important new tool in the last twenty years for understanding the structure and evolution of morphology. The arthropod head problem has been tackled in three main ways in this regard, first by using genetic segmental markers to probe the obscure region in front of the mouth, especially in insects; second by looking at Hox gene expression patterns to detect patterns of homology between different arthropods; and third, by studying gene expression in particular features (especially the labrum) to determine its appendiculate or other status. Because all arthropods have the same complement of nine Hox loci, the morphological diversification observed is caused by these genes being expressed at different areas and times.
Read more about this topic: Arthropod Head Problem
Famous quotes containing the words development, head and/or problem:
“Other nations have tried to check ... the fulfillment of our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.”
—John Louis O’Sullivan (1813–1895)
“Therefore with idle hands and head I sit
In late December before the fire’s daze
Punished by crimes of which I would be quit.”
—Allen Tate (1899–1979)
“The problem of the novelist who wishes to write about a man’s encounter with God is how he shall make the experience—which is both natural and supernatural—understandable, and credible, to his reader. In any age this would be a problem, but in our own, it is a well- nigh insurmountable one. Today’s audience is one in which religious feeling has become, if not atrophied, at least vaporous and sentimental.”
—Flannery O’Connor (1925–1964)