Princeton University
Department of Molecular Biology

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Tiger Talks


Understanding development: From genetics to genomics

Thu, Nov 12, 2009
Location - TBA


Professor of Molecular Biology


On a crisp fall evening, Professor Eric Wieschaus welcomed over 550 enthusiastic students and teachers for his TIGER Talk titled "Understanding development: From genetics to genomics". His research career has been centered on a profound truth: that we all started out our existence as a single cell. He shared with the audience how the extraordinary process of one cell becoming a complicated organism fascinated him as a young scientist. To demonstrate his wonder, he showed video clips of the early divisions in a human and sea urchin embryo. Prof. Wieschaus then explained that the same process also occurs in Drosphila, but at a much faster pace so they are ideal model organisms. As a scientist he asked "How do cells know what to do and when to do it? Are there specific genes involved?" He and his colleague, Christiane Nüsslein-Volhard (see ) decided to answer the question by adopting a genetic approach. They made random mutations using X-rays or mutagens and set up crosses for three generations. When they were planning the experiments, they soon realized that this would involve at least 40,000 tubes of flies! They were young, energetic scientists and fortunately no one discouraged them from their quest. Eventually, while searching for visible lethal mutations, they narrowed the search to 586 mutant lines of Drosophila. From these they identified 139 genes that are essential for embryogenesis. This same experiment can be approached today using microarrays, since the Drosophila genome has been sequenced. Microarrays can tell us how many genes are being expressed. Results show about 6,000 RNAs are expressed in the embryo. How many are transcribed? The answer is 1200. Unlike the 139 genes detected by the genetic approach of 30 years ago, the vast majority of the 1200 genes, detected by microarray, do not have visible effects. Therefore a small number of genes produce easy to recognize phenotypes and play a central role in controlling development. Two of these mutants are expressed in embryonic mesodermal cells immediately prior to movement into the furrow. They were named "twist" and "snail". In humans these same genes are associated with certain birth defects and are mis-expressed in some human tumors during metastasis. Professor Wieschaus stressed that we can learn about human genes by analyzing fly genes and we can learn about fly genes by comparing what they do in other organisms. Genes are shared across all animals and even plants. During the exciting last few minutes of his talk, Prof. Wieschaus shared memories and video clips of his Nobel Prize award and ceremony on December 10, 1995.

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