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But now, a century and a half later, scientists from 11 different institutions have joined forces to amass all of that information, plus new data, to create the most comprehensive version of the tree so far. As detailed in a recent article in Proceedings of the National Academy of Sciences, the new Tree of Life
shows how 2.3 million different types of animals, plants, fungi and microbes are interconnected, and how those relationships have diverged since life began on Earth more than 3.5 billion years ago.
This case study centers on symbiotic relationships between insects and bacteria using Drosophila melanogaster, the common fruit fly, and the recently discovered bacterial species Sodalis praecaptivus. Until recently, the only known Sodalis species of bacteria were symbiotically associated with several different species of insects. However, free-living non-symbiont Sodalis species are being tested in several different insect species to determine if they can transition into symbiotic relationships. A pre-class assignment (see Supplemental Materials) directs students to read an open access research journal article providing a comprehensive review of S. praecaptivus and describing an experimental weevil model that parallels that of the fruit fly. A PowerPoint presentation shown in class (see Supplemental Materials) provides further background before students work in small groups to complete the case study focusing on results from D. melanogaster and S. praecaptivus model experiments. Although developed for a genetics course, this interrupted case is appropriate for an upper-level biology course. It can be completed within a 75-minute class meeting, or adapted for shorter time periods.
The behavior of a person's genes doesn't just depend on the genes' DNA sequence - it's also affected by so-called epigenetic factors. Changes in these factors can play a critical role in disease.
LifeMap Discovery® is a compendium of embryonic development for stem cell research and regenerative medicine, constructed by integrating extensive molecular, cellular, anatomical and medical data curated from scientific literature and high-throughput data sources.