Genome complexity: telling which cells to develop. (Introduction)

by David Turell , Friday, December 23, 2016, 21:49 (2892 days ago) @ David Turell

In embryology early generalized cells have to b e told which final type of cell they should. Specific chemical are produced to control this:

http://medicalxpress.com/news/2016-12-embryonic-fate-skin-cells-sweaty.html

"A team of researchers with the Rockefeller University has identified the signals and timing that are involved during embryonic development controlling whether skin cells grow to be sweaty or hairy.

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"Mice are unique because they have skin cells on their backs that only allow for the development of hair follicles and skin cells on their feet that only allow for the development of sweat glands. This allowed the researchers an opportunity to learn more about such development by comparing the two. They found that stem cells that led to skin development in mice had differences in RNA expression of proteins that were involved in controlling which type of cell structure would develop—one type, called mesenchymal-derived bone morphogenetic proteins, were, for example, more plentiful in cells found in the feet—one in particular, Bmp5, was found to play a particularly important role. When it was blocked, the number of sweat glands that developed in mice feet was greatly reduced. The team also found other mechanisms involved, such as WNT and FGF proteins, which, when switched in mice, resulted in cells developing swapped end results, e.g. hair follicles instead of sweat glands.

"The team compared these results with human skin cell samples and found that BMP and FGF proteins were expressed at higher levels during week 17 of fetal development than during week 15, which prior research has shown is a period when skin cell progression moves from hair to sweat-bud formation."

Comment: Note the complexity here. In the development of the embryo, timing is everything so parts form in proper sequence and relationship to all other parts. Chemical signals must appear on time to create the proper cells in the proper place. Cells become either hair or sweat glands, but there are also oil glands not mentioned in this article. All start from the same progenitor cell. How the chemicals listed in the article teach the DNA in each cell to differentiate the cell into the exact type needed is currently unknown. There is also the issue of proper placement of oil and sweat glands and the hair follicles. And evolution developed all of this process by chance. No way! This biology alone negates Darwin's thoughts about evolution. His only contribution is the concept of evolution by common descent, nothing of the methodology of how it happened.