To complete their work, the research team aligned 7,442 genes from the python and cobra with genes sequences available in the Ensembl Genome Browser from other amphibians, reptile, bird and mammals. They used a statistical method called "branch site codon modeling" to look for genes that had been positively selected (or evolutionarily changed due to natural selection) in the python, the cobra, and early in snake evolution in the common ancestor of these two snakes. They found changes in hundreds of genes. They believe the results demonstrate that natural selection-driven changes in many genes that encode proteins contributed substantially to the unique characteristics of snakes.
Analyses showed a remarkable correspondence between the function of the selected genes, and the many functionally unique aspects of snake biology such as their unique metabolism, spine and skull shape and cell cycle regulation, Castoe said. Many of the altered genes the team observed also have prominent medical significance. For example, the python genome showed some changes to the gene GAB1, which other research suggests plays a role in breast cancer, melanomas and childhood leukemia.
In addition to changes to individual genes and their expression, researchers also found that the extreme characteristics in snakes could also be linked to duplications or losses in multigene families. Some of those include ancient loss and more recent re-evolution of high resolution vision, and their ability to detect chemical cues from the environment. Researchers also observed that, while most assume that reptile genes and genomes change
|Contact: Traci Peterson|
University of Texas at Arlington