{"73656":{"#nid":"73656","#data":{"type":"news","title":"Fishing for the Origins of Genome Complexity","body":[{"value":"\u003Cp\u003EBiologists at Georgia Tech have provided scientific support for a controversial hypothesis that has divided the fields of evolutionary genomics and evolutionary developmental biology, popularly known as evo devo, for two years. Appearing in the December 2005 issue of Trends in Genetics, researchers find that the size and complexity of a species\u0027 genome is not an evolutionary adaptation per se, but can result as simply a consequence of a reduction in a species\u0027 effective population size. \u003C\/p\u003E\n\u003Cp\u003E\u0022As a general rule, more complex organisms, like humans, have larger genomes than less complex ones,\u0022 said J. Todd Streelman, assistant professor in the School of Biology at the Georgia Institute of Technology and co-author of the study. \u0022You might think this means that animals with the largest genomes are the most complex - and for the most part that would be right. But it\u0027s not always true. There are some species of frogs and some amoeba that have much larger genomes than humans.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ETo help explain this paradox, a pair of scientists from Indiana University and the University of Oregon published a hotly-contested hypothesis in 2003. It said that most of the mutations that arise in organisms are not advantageous and that the smaller a species effective population size (the number of individuals who contribute genes to the next generation), the larger the genome will be. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022We agreed with some of the criticisms of the hypothesis - that one had to remove the effects of confounding factors like body size and developmental rate,\u0022 said Streelman. \u0022We were able to remove the effects of these confounding factors and test whether genome size is adaptive.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ETheir test consisted of analyzing data from 1,043 species of fresh and saltwater ray-finned fish. Previous data on genetic variability had established that freshwater species have a smaller effective population size than their marine counterparts. If the hypothesis was correct, the genome size of these freshwater fish would be larger than that of the saltwater dwellers. It was. \n\u003C\/p\u003E\n\u003Cp\u003EThen they matched the data with estimates of heterozygosity, a measure of the genetic variation of a population. Again they found that species with a smaller effective population had larger genomes.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We see a very strong negative linear relationship between genome size and the effective population size,\u0022 said Soojin Yi, assistant professor in the School of Biology and lead author of the study. \u0022This observation tells us that the mutations that increase the genome tend to be slightly deleterious, because population genetic theories predict such a relationship.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u0022The interesting thing here is that biological complexity may passively evolve,\u0022 said Yi. \u0022We show that at the origins, it\u0027s not adaptive mutations, but slightly bad ones that make the genome larger. But if you have a large genome, there is more genetic material to play with to make something useful. At first, maybe these mutations aren\u0027t so good for your genome, but as they accumulate and conditions change through evolution, they could become more complex and more beneficial.\u0022\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Deciphering a paradox of evolution"}],"field_summary":[{"value":"Biologists at Georgia Tech have provided scientific support for a controversial hypothesis that has divided biologists for two years.","format":"limited_html"}],"field_summary_sentence":[{"value":"Research results bolster a controversial hypothesis"}],"uid":"27310","created_gmt":"2005-12-15 01:00:00","changed_gmt":"2016-10-08 03:00:59","author":"David Terraso","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2005-12-15T00:00:00-05:00","iso_date":"2005-12-15T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"73657":{"id":"73657","type":"image","title":"Mola Mola","body":null,"created":"1449178002","gmt_created":"2015-12-03 21:26:42","changed":"1475894385","gmt_changed":"2016-10-08 02:39:45"}},"media_ids":["73657"],"related_links":[{"url":"http:\/\/www.earthwindow.com\/","title":"Photo courtesy of earthwindow.com"},{"url":"http:\/\/www.biology.gatech.edu\/faculty\/todd-streelman\/","title":"Todd Streelman"},{"url":"http:\/\/www.biology.gatech.edu\/faculty\/soojin-yi\/","title":"Soojin Yi"}],"groups":[{"id":"1214","name":"News Room"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EGeorgia Tech Media Relations\u003C\/strong\u003E\u003Cbr \/\u003ELaura Diamond\u003Cbr \/\u003E\u003Ca href=\u0022mailto:laura.diamond@comm.gatech.edu\u0022\u003Elaura.diamond@comm.gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-894-6016\u003Cbr \/\u003EJason Maderer\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-660-2926\u003C\/p\u003E","format":"limited_html"}],"email":["david.terraso@comm.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}