Chimps and Humans

Biological anthropologist often repeat the mantra that chimps and humans share a large portion of their genomic content (between 95-99% depending on who you ask and what types of markers you are looking at). So if we share this much DNA then why do chimps and humans look so different (depends on your point of few, case in point pictures below). Well Science Daily has an interesting little article how Canadian researchers are investigating how these differences might arise due to gene splicing. This indicates that while the actual nucleotide sequences are similar the proteins being produced are different. The abstract from the article is below and here.

This is actually important from an evolutionary standpoint. A common misconception of the public is that evolution is linear (la scala naturae) with humans at the top of the ladder. Technically, were a rung down from angels and that original G fellow but who's counting. This also extends to the idea that we somehow evolved from a chimpanzee without realizing we share a common ancestor with chimps in our species evolutionary journey. Since that time we have gone our separate ways and natural selection has often acted on different traits in each species. This article goes a long way in helping us better understand how even though genes may look the same the way they are spliced and put together may result in completely different organisms.

Global analysis of alternative splicing differences between humans and chimpanzees

John A. Calarco^1,2,8, Yi Xing^3,4,8, Mario Cáceres^5,6,8, Joseph P. Calarco¹, Xinshu Xiao⁷, Qun Pan¹, Christopher Lee³, Todd M. Preuss^5,10, and Benjamin J. Blencowe^1,2,9

Alternative splicing is a powerful mechanism affording extensive proteomic and regulatory diversity from a limited repertoire of genes. However, the extent to which alternative splicing has contributed to the evolution of primate species-specific characteristics has not been assessed previously. Using comparative genomics and quantitative microarray profiling, we performed the first global analysis of alternative splicing differences between humans and chimpanzees. Surprisingly, 6%–8% of profiled orthologous exons display pronounced splicing level differences in the corresponding tissues from the two species. Little overlap is observed between the genes associated with alternative splicing differences and the genes that display steady-state transcript level differences, indicating that these layers of regulation have evolved rapidly to affect distinct subsets of genes in humans and chimpanzees. The alternative splicing differences we detected are predicted to affect diverse functions including gene expression, signal transduction, cell death, immune defense, and susceptibility to diseases. Differences in expression at the protein level of the major splice variant of Glutathione S-transferase omega-2 (GSTO2), which functions in the protection against oxidative stress and is associated with human aging-related diseases, suggests that this enzyme is less active in human cells compared with chimpanzee cells. The results of this study thus support an important role for alternative splicing in establishing differences between humans and chimpanzees.