Stadler proposes to study the rate at which reccessive lethal mutations arise in neurospora. Neurospora is an ideal organism for this type of investigation since it is coencytic (i.e., multinucleate). Previous studies that used a variety of other organisms have suffered from the appearance of rare variants that outgrow other members of the culture and thus make it difficult to establish true growth and mutation rates. The presence of the lethal mutations can be detected by screening the offspring of uninucleate asexual spores (conidia). The use of appropriately marked laboratory stains will facilitate the somewhat tedious process of screening. He will also examine mutations that give rise to drug resistance, which can be detected by selective techniques. For the latter, wild isolates of the fungus can be used. Stadler hopes that some of these drug resistance mutations will result from insertion of a transposable element, and has devised an appropriate scheme to recover the element if observed. There are a variety of known causes for heritable alterations (mutations) in the genomes of all organisms. These include errors committed during the replication of normal DNA, as well as damage resulting from exposure to chemicals (natural and man-made) and radiation. In the last few years, a great deal has been learned about the effects of exposure to relatively high levels of chemicals and radiation. However, the extrapolation of this data to form conclusions about the effects of exposure to the low levels likely to be encountered under natural conditions has been a subject of considerable controversy. The proposed work, by providing information about rates of spontaneous mutation will help to remedy this situation, and may help to evaluate the relative importance of the natural causes of mutation mentioned above.
