Newmeyer, D.

Fungal Genetics Reports

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D. Newmeyer

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Altered phenotype of phen

Kansas State University

Fungal Genetics Reports Volume 4 Article 8 Altered phenotype of phen D. Newmeyer Follow this and additional works at: https://newprairiepress.org/fgr This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License. Recommended Citation Newmeyer, D. (1963) "Altered phenotype of phen," Fungal Genetics Reports: Vol. 4, Article 8. https://doi.org/10.4148/1941-4765.2153 This Research Note is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Fungal Genetics Reports by an authorized administrator of New Prairie Press. For more information, please contact cads@k-state.edu. Altered phenotype of phen Abstract Altered phenotype of phen This research note is available in Fungal Genetics Reports: https://newprairiepress.org/fgr/vol4/iss1/8 Newmeyer, D. Altered phenotype of phen (H6196) was originally reported to grow essentially phen. Gild type on phenylalonine, and slightly more slowly on other aromatic amino acids, or leucine, or ethyl- ocetoacetote (Borratt and Ogota, A. J. Bat. 41, 763 (1954)). H owever, several workers hove noticed that isolates of this mutant often lose their amity to respond well to phenylolanine (Borratt, Perkins, Barry, St. Lawrence, and Maling, personal communications). Wh’l I e such isolates ore still clearly mutant, being unable to grow on minimal, their occurrence presents o scoring problem in crosses in which other nutritional or slow-growing types are segregating. The following results were obtained during on attempt to solve the scoring problem. They ore based on tests in 3” tubes at 25”; no quonti- tative tests have been done. I. “Fat” phen isolates (the original phenotype) regularly give fair to good growth in 2 days on minimal plus phenylolanine. Growth on leucine is somewhat slower. 2. “Slow” phen isolates (the altered phenotype) give negligible growth in 2 days on minimal plus phenylolanine;fairgrowth moy occur in 3 days but usually takes 4 to 7 days. Increasing the phenyl- alanine concentration from .I to .5 mg/cc does not help. On leucine, fair to good growth usually occurs in 3 days but occasionally takes 4 to 7 days. A combination of leucine plus phenylalanine is perhaps slightly better than leucine alone. On all 3 media, the length of the lag period is quite variable in re- peated tests with the some isolate. Scoring is possible (although tedious) because no slow phen has yet been found to grow on minimal in 7 days. Preliminary tests indicate that growth of slow phen’s on ethyl ocetoacetate is not impoired. 3. The growth of slow phen’s on glycerol corn-s strongly inhibited by the addition of I% sucrose. This inhibition is usually outgrown after o variable lag. With fast phen’s, the inhibition is usually (but not always) considerably weaker. Of eight other biochemical mutants tested, none has shown such on inhibition. A series of 45 isolates from o cross of phen x org-I, previously scored for phen by grwth on _- phenylalanine and leucine, gave identical results when scored by sucrose inhibition. 4. Since it seemed that the delayed growth on phenylalonine might be due to inhibition by the sucrose in the medium, sever01 isolates were tested on minimal plus phenylolonine with various carbon sources. It was found that using dextrose, or lowering the sucrose concentration to 0.25%, did not help, but that using glycerol caused a much more rapid response. The substitution of glycerol for sucrose in minimal medium reduces the growth rate slightly even for wild type; however, all slow and fast phen’s tested grew ot least os fast os the wild type controls on glycerol minimal plus phenylolonine. It thus seems that the difference between fast ond slow phen’s may be (I matter of differing sensitivity to sucrose. It is not known why this sensitivity should be mOreserious when the supplement is phenyl- olanine rather than leucine or ethylacetwcetate. The question arises whether these compounds ore needed solely to combat the sucrose inhibition; preliminary tests indicate that this is not the case. 5. It has not been determined whether the change from fast phen to slow phen is due to o modifier or to o change ot the phen locus itself. --Deportment of Biologicxciences, Stanford University, Stanford, California. Prakash, V. Changes in cross-over During recent years, o number of workers have recorded frequency in Neurospora crosso mediated modifying effects on the frequency of genetic exchanges by by chelating agents. employing primarily one chelating agent, ethelenediamine tetroocetic acid (EDTA). It is presumed that this ogent facilitates in breaking the linear continuity of the chromotids incidental to crossing-over os it chelates metallic ions, especially calcium and magnesium, essential to the maintenance of structural integrity of chromosomes. In the present study, EDTA ond another chelating agent, 8-hydroxy quinoline were used. To screen the effects of different concentrations of EDTA and 8-HQ on the frequency of crossing-over, ascospores, representing the pop,xlation of meiotic prc&cts of the crosses made in Neurospora cro:so, were plated on o selective medium in whish o,~ly particular recombinonts could grow. After heat shock, the plates were incubated ot 25’ C. Depending on the approximate size of colonies from the germinated oscospores, the initial score was done after I6 to I8 hours of incubation, and to store ascospores with delayed germination 

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Altered phenotype of phen

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