The Disappearance of Snake Legs

Snakes have lost their legs about 150 million years ago due to a DNA composition change that created a mutation to get rid of legs. This has been confirmed two separate times by two separate groups of scientists. We know that snakes used to have legs because through dissection experiments of boas and pythons and other snakes, we can find tiny receded bone groups that seemed to be used as legs before.

"Mutations in DNA located near a gene key to limb formation keep that gene rom ever turning on"

The snakes at first were looked at under the mutation of the hedgehog gene that we learned about before in class. So they analyzed the sonic the hedgehog gene and they noticed that there were three deletions and a modified enhancer within snakes. In order to study this enhancer a special technique called CRISPR-Cas9 was used.

"CRISPR-Cas9 is a unique technology that enables geneticists and medical researchers to edit parts of the genome by cutting out, replacing, or adding parts to the DNA sequence"

When the snake enhancer was put into a mouse, the issue was that the mouse grew very stubby legs. When the snake enhancer was repaired with the missing deletions and then put into the mouse, it grew normally. This is molecular genetic evidence for snakes that used to have legs.

I am very excited to see how genetics is now affecting the idea of phylogenies and relationships between animals because for a long time scientists have been using taxonomy in order to project phylogeny, but the only way to truly study relationships is on the genetic and molecular level. Studies like this will continue amending the phylogenies we have developed thus far to be more accurate in telling us how things tacked back to their common ancestors and evolved.

What Turns Genes On and Off?

     A team of researchers from Perelman School
of Medicine at University of Pennsylvania have
shed light on how structure of regulatory sequences in DNA is packaged in a cell. The research gives a better understanding of how gene sequences, contribute to gene activity. Enhancers are what influences genes in each cell to be turned on or off. The ultimate purpose of this is to dictate the quality of an encoded protein that is made in response to a physiological change. The following link gives further insight to gene expression and how they can be turned on and off. One reason this research is so important is that many studies have shown errors in enhancers lead to disease or cancer.

      Nucleosomes are a protein that DNA winds around in every cell, and in the past it was believed that when nucleosomes are present the surrounding genes are turned off; therefore not playing a role at enhancer sites. This study provides data to dispute this recently believed theory, and nucleosomes are present at enhancer sites.

     The team of researchers found that certain stretches of DNA were bound to nucleosomes and could be modified to have genes turned on. They removed linker histones from DNA, and allowed enhancers to activate that a single gene which caused the cell to function normally. The team believes this is very promising, because with these techniques cancers and disease can be fought. Also it can be useful in embryo therapy.

      I agree that this study shows very promising results. If scientist can learn to completely turn genes on or off it will cause medical break throughs. It will gives doctors a new angle on fighting disease and forms of cancer. These advancements can also help correct errors in developing embryos or fetuses.

Engineers Gain Control of Gene Activity

Charles Gersbach

Researchers at Duke University in North Carolina have developed a new technology to manipulate proteins that package our DNA, and by doing so are able to turn on specific gene promoters and enhancers - DNA sequences that influence the activity of their corresponding genes. The ability to do this allows for control of gene activity. The combination of all molecules responsible for the activity of genes in the genome is known as the epigenome, and is the main subject of attention for this current research. The ability to alter the actions of the epigenome allows researchers to see what roles the promoters and enhancers play in many biological contexts, including cell fate, risk of diseases, and stem cell research.

Assistant professor of biostatistics and bioinformatics at Duke University Timothy Reddy teamed up with Charles Gersbach to modify the previously established system called CRISPR to alter DNA packaging at specific sites. This process allowed not only for activation of gene promoters but also for the activation of adjacent genes. The developed method has worked better at accomplishing this task than other methods previously tried.

The true benefit to this research is the effect it may have on understanding and diagnosing modern day diseases such as neurodegenerative conditions and cancer. Many diseases are quite complex genetically, as there may be many enhancers and/or promoters that affect the activation of genes that cause the expression of a disease. Being able to isolate these enhancers and promoters in the epigenome may provide paramount insight into the treatment of modern diseases.