Snake leg loss genes found, according to reports in Science (AAAS) News 20 October 2016, Current Biology doi: 10.1016/j.cub.2016.09.020, published online 20 October 2016 and Cell, Vol. 167, p633–642.e11, doi: 10.1016/j.cell.2016.09.028 20.
The most characteristic features of snakes are their long body form and lack of legs. Pythons and boas have tiny bony limb remnants ending in small claw-like projections on their bodies, but most other snakes have no limb structures at all. Previous studies have shown the snakes’ long body with its multiple ribs, is the result of an overactive growth enhancer gene that makes the spine and ribs keep growing during embryonic life.
Two groups of scientists have now found gene mutations that result in loss of limbs in snakes. Martin Cohn and Francisca Leal of University of Florida studied genetic activity during embryonic development in pythons. Like other reptiles python embryos start to develop a hind limb bud but this fails to grow into a leg. Cohn and Leal found the failure was due to three DNA deletions in the genetic switch that enhances the activity of a gene called Sonic hedgehog (SHH). The Sonic hedgehog gene is needed for proper limb development and the damaged gene switch means it is only turned on for a brief time, not long enough to form a proper limb. In completely legless snakes the genetic switch has even more deletions, which probably means the Sonic hedgehog gene is never turned on.
They wrote in their report: “Our results suggest that degenerate evolution of the SHH limb enhancer played a role in reduction of hindlimbs during snake evolution”.
Another group of scientists have also studied the Sonic hedgehog enhancer. Axel Visel and colleagues from Lawrence Berkeley National Laboratory, California and University of Basel, Switzerland, used a gene editing technique named CRISPR-Cas9 to replace the SHH enhancer in mice with a snake version containing deletions and mutations. These transgenic mice had severely reduced limbs. The scientists then replaced the mutated gene enhancer with a normal version and the mice grew normal limbs.
The research team wrote in their report: “Our results demonstrate changes in a regulatory sequence associated with a major body plan transition and highlight the role of enhancers in morphological evolution”.
Science. Also see video summary of research on Current Biology, click on “video abstract”.
Editorial Comment: The more we study snakes the more we find that the characteristic long body form and lack of legs is due to garbled growth controlling genes. This is degeneration and loss – the opposite of evolution. The fact that snakes can function with these characteristics is not evolution either. It is simply survival. All reptiles with legs move with S shaped body motion and the snake has merely maintained this already existing form of motion.
Previous studies have also shown a hox-type gene link between reptile leg loss and body lengthening, which put altogether means there should be no problem for anyone believing that God could condemn a short bodied creature that originally walked on four legs to becoming a long bodied gliding creature with no legs. All it takes is for its growth control genes to degenerate, which is exactly what has been found by these genetic studies of snakes. The more we get to know about how genes are controlled, and how they have gone wrong, the more scientists are truly without excuse for ignoring their Creator and Saviour.
Evidence News vol. 16, No. 20
2 November 2016
Creation Research Australia
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