by Angela WongRecent discoveries may help shed light on what makes us all unique, and why even identical twins can be so unlike (Salk, 2016). These findings have large implications on not only what distinguishes us from one another, but also on what sets Homo sapiens apart from other eukaryotes. In a sense, these factors simultaneously define and unite us. LINE-1 retrotransposons (L1s), also called “jumping genes,” are small pieces of DNA that have been known to insert genetic information throughout the genome. “Jumping” around the genome, they amplify themselves which lead regulatory DNA to be copied and shuffled (Ivancevic, Kortschak, Bertozzi et al., 2016). Present in most healthy neurons, L1s are a source of genomic diversity on the brain. Variations between neurons within the same brain suggest that they “function slightly differently from each other,” says the study’s senior investigator, Rusty Gage. Due to L1s and other factors, each neuron contains around 1,500 unique mutations (Yong, 2015). Diversity of neurons, which process and transmit information in the brain, impacts one’s brain functionality (Salk, 2016). Additionally, at least a third of the 20,000 different genes in the human genome are expressed in the brain—the highest proportion of genes expressed in the human body. According to latest studies, L1s can also remove large chunks of DNA, affecting the genome even more significantly than previously thought. Evidence has shown that neurons from those with schizophrenia and Rett syndrome have above-average levels of L1 variations within their genomes. Researchers at the Salk Institute believe that these findings indicate will further the understanding of the role, and they plan to continue exploring the role of L1 variations and how they impact both brain function and illness (Salk, 2016). Other scientists conducted a “comprehensive phylogenetic analysis of elements from over 500 species from widely divergent branches in the tree of life” to examine the diversity of L1s, which are thought of as “tightly constrained, homologous, and ubiquitous elements with well-characterized domain organization.” They found that in recent times, the growth of L1 elements in mammalian species have diverged from lineages in other plants and metazoans, animals with cell differentiation. Illustrating that “both long-term inherited evolutionary patterns and random bursts of activity in individual species can significantly alter genomes” (Ivancevic et al., 2016). These two studies highlight the significance of L1s in the expression of characteristics that make each one of us unique, as well as uniquely human. Sources: Ivancevic, A. M., Kortschak, D., Bertozzi, T., & Adelson, D. (2016, September 26). LINEs between species: Evolutionary dynamics of LINE-1 retrotransposons across the eukaryotic tree of life. Genome Biology and Evolution. Retrieved from http://gbe.oxfordjournals.org/content/early/2016/09/30/gbe.evw243.abstract The brain’s stunning genomic diversity revealed - Salk ... (2016, September 9). Retrieved October 21, 2016, from http://www.salk.edu/news-release/brains-stunning-genomic-diversity-revealed/ Yong, E. (2016, October 1). The Surprising Genealogy of Your Brain - The Atlantic. Retrieved October 21, 2016, from http://www.theatlantic.com/science/archive/2015/10/the-genealogy-of-your- brain/408232/
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AuthorsThe authors of these blog posts are staff writers of The Triple Helix at Georgetown University. Archives
November 2016
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