I am going to explain to you why for snakes have no legs. Trained in genetics, I will explain really the aspect of “how” snakes have evolved to have no legs.
To begin, the genes that control the development of body parts in an organisms are known as the Homeobox genes normally referred to as HOX Genes. These genes are a magical set of genes that determine any appendage that developes; the digits of your hand, the limbless abdomens , the various feeding and walking and swimming limbs. These genes are in clusters in the genome and the interesting part is that they are found in DNA in the order to which they develop.
This part really is mindboggeling because from my current understanding scientist still can not find any evidence definitively proving why this is the case. In many other case genes that have to do with each other, sometimes involved in the same protein can be found thousands of basepairs away from each other, sometimes even on completely separate chromosomes. Nevertheless, this mystery has brought with it many interesting hypotheses.
Furthermore, because all animal come from a common ancestor the genes that code for a fly thorax(chest) is highly identical to any other creature. So if you look at a snakes genome, what you see in almost all of its cells the thorax hox genes being expressed. And their Leg and arm genes are not being expressed. Infact this picture below shows hows snakes actually used to have legs.
Also, just some humans are born with tails that have normally evolved away, some snakes are actually born with vestigial legs.
What we have all been waiting for! SO why do snakes no longer have legs? It is not like snakes no longer have the genes to make these appendages, it's simply that they no longer express those genes in development. Although snakes do not promote the expression of their limb genes scientists can splice in DNA enhancers that give them the protein that is used for activating thoes Hox genes. Although they could not continue to produce the protein all the way through development they did get some pictures while they were still developing in the egg. What scientists found was that this protein was like snake Viagra!!! Crazily enough it made them develop large penises.
When they took snake enhancer sequences and put them into developing mouse embryos; they found that the snake DNA segments did not activate the mouse legs. However, those genes did active penis growth in the mice as well! In other words this DNA enhancer was also a male enhancer! haha As the slow progression of snakes not needing to use their legs the DNA enhancer to promoter their growth found another function through evolution. A DNA reassignment if you will; something that is quite common in evolution.
I hope you all enjoyed that interesting adventure into snake genetics! As a reward I have this really cute 40sec snake video, of a snake playing with his new toy! The end is the best!! Dont forget to follow me for more interesting posts!! And please upvote so I can justify spending my time, I truly need and would appreciate everyone's support=(
If anything upvote for that cute snake head at the end=)