Genes, Environment, or Chance?

Despite identical genes and a shared environment, only some mutant nematode embryos develop a gut, which appears violet in this photomicrograph. (Credit: Arjun Raj and Scott Rifkin) Biologists attribute variations among individual organisms to differences in genes or environment, or both. But a new study of nematode worms with identical genes, raised in identical environments, has revealed another factor: chance. It's another source of variation for scientists to consider. 'Researchers have been exploring whether organisms evolve different ways to cope with genetic and environmental variation,? said author Scott Rifkin, an assistant professor of biology at UC San Diego. 'This study adds random variation to that mix.' Rifkin, who joined the UCSD faculty this fall, completed the study while working at MIT. The paper, co-authored by Arjun Raj, who contributed equally to Rifkin and his colleagues looked at the development of the gut in C. elegans. In many, but not all worms with mutations in a gene called skn-1 , the gut failed to develop, even when the embryos were genetically identical and incubated together. ?Often when people look at variation in a trait among organisms they try to trace it back to genetic differences or differences in environmental conditions or some combination of the two. In our study there were no such differences, and so we hypothesized that the only other source for the variation could be differences that arose at random during the process of development,?