When a series of 50 tubes of broth containing 0.5% sodium ribonucleate (Schwartz) is inoculated with strain B/r of Escherichia coli, the cultures obtained after 48 hours of incubation contain, on the average, a significantly higher number of mutants resistant to bacteriophage T 1 than a similar series of cultures grown without nucleate

Witkin,  Evelyn M.

Cold Spring Harbor Laboratory Institutional Repository

141 of males  produced c r o s s o v e r s  a l so  in a nonrandom manner  appropriate to spermatogonial  c ross ing  over.  data for  s tandard maps  a r e  considered. The implications to the collection of WHITTINGHILL, MAURICE, University of North Carol ina,  Chapel Hill ,  N. C.: f r o m  Curly inversion heterozygotes of Drosophila melanogaster .  - Eighteen Cy It L 4  heterozygotes having 7,477 offspring in  two-day coded cul tures  produced 28 spontaneous c r o s s o v e r s  non-randomly. too many similar p a i r s  and t r iplets .  Considering only famil ies  missed  and one family having four region-one c r o s s o v e r s ,  a joint  probability of 1.6 X 10 -8 was computed. Recombinations decreased great ly  with age indicating that the age effect is c rea ted  in oijgonial cel ls  ra ther  than during meiosis .  The non-random distribution of spontaneous c r o s s o v e r s  --- --There  w e r e  WITKIN, EVELYN M., Carnegie Institution of Washington, Cold Spring Harbor ,  N. Y.: ichia coli. - When a s e r i e s  of 50 tubes of broth containing 0.5% sodium ribonucleate (Schwartz) is inoculated with s t ra in  B/r of Escherichia  col i ,  the cul tures  obtained after 48 hours  of incubation contain, on the average,  a significantly higher number of mutants res i s tan t  to bacteriophage T 1 than a similar s e r i e s  of cul tures  grown without nucleate. The higher number of mutants is not due to an increased rate of mutation during growth in nucleate. Nucleate cul tures  and broth controls  do not differ in frequency of phage-resistant mutants a t  the end of the logarithmic growth phase. "stationary" phase.  the division of phage-resistant mutants ,  nor to m o r e  active total  division of the nucleate cul tures .  Analysis of the data suggests that  nucleate brings out the phenotypic expression of spontaneous delayed mutations,  which would ordinar i ly  be detected as res i s tan t  only af ter  passing through one o r  m o r e  divisions. This hypothesis is supported by experiments  using ultraviolet-irradiated populations known to contain la rge  numbers  of in- duced delayed mutations.  Under cer ta in  conditions, nucleate can  take the place of division in bringing out the phenotypic expression of ul t ra-  violet-induced delayed mutations. Similar  resu l t s  have been obtained with high concentrations of casein hydrolysate. Effect of nucleic acid on phenomic lag in  Escher -  ----- --The difference appears  only as the cul tures  a r e  incubated in  the The effect is not due to differential st imulation of 

Effect of nucleic acid on phenomic lag in Escherichia coli

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