Magic embryology: GPS for forms (Introduction)

by David Turell , Thursday, November 11, 2021, 18:12 (1239 days ago) @ David Turell

Well outlined:

https://theconversation.com/genetic-gps-system-of-animal-development-explains-why-limbs...

"While human body shape and appearance have clearly changed during the course of evolution, some of the genes that control the defining characteristics of different species surprisingly have not. As a biologist studying evolution and development, I have devoted many years to pondering how genes actually make people and other animals look the way they do.

"New research from my lab on how these genes work has shed some light on how genes that have remained unchanged for hundreds of thousands of years can still alter the appearance of different species as they evolve.

***

"Hox genes play an important role in setting up this body plan. This group of genes is a subset of genes involved in anatomical development called homeobox genes. They act like a genetic GPS system, determining what each body segment will turn into during development. They ensure that your limbs grow from your torso instead of from your head by controlling other genes that instruct the formation of specific body parts.

All animals have Hox genes and express them in similar body regions. Furthermore, these genes haven’t changed throughout evolutionary history. How can these genes remain so stable over such vast evolutionary time spans, yet play such pivotal roles in animal development.

***

"The next big question, then, was how exactly do these Hox genes determine the identities of different body regions?

"There have been two schools of thought on how Hox genes work. The first, called the instructive hypothesis, proposes that these shape-controlling genes function as “master” regulatory genes that supply the body instructions on how to develop different body parts.

"The second, proposed by McGinnis, hypothesizes that Hox genes instead provide a positional code that marks particular locations in the body. Genes can use these codes to produce specific body structures at those locations. Over the course of evolution, specific body parts come under the control of a specific Hox gene in a way that would best maximize the organism’s survival. This is why flies develop antennae rather than legs on their heads, and humans have collar bones below instead of above their necks."

Comment: Sexual reproduction always produces the same infant forms. Although the research is still ongoing, we still don't know exact mechanisms of control. But the instructional information always produces the same results with minor variations. This is a pure example of cellular automaticity. Automatic sameness is automaticity in fetal production.