Section 4 — Gene action 



occur independently at a and (3 each having its 

 own particular frequency and character. 



From these observations it is clear that a type 

 of instability of obscure origin is able to appear 

 at a compound locus and then to move back and 

 forth between the components of this locus, 

 affecting each as though it were a separate gene. 



4.26. Variegation following Hybridization between 

 Nicotiana tabacum and N. otophcra. 

 D. U. Gerstel, and Joyce A. Burns (Raleigh, 

 U.S.A.) 



Different mechanisms seem to cause chloro- 

 phyll, bud anthocyanin and flower anthocyanin 

 variegations obtainable after hybridization of 

 TV. tabacum with N. otophora. The first two types 

 can be recognized only in later generations after 

 recombination has taken place. Carmine-coral 

 flower variegation occurs as a rule in first gener- 

 ation hybrids between coral N. tabacum and 

 N. otophora: this type has been sufficiently in- 

 vestigated for a preliminary report. It differs as 

 follows from the variegations described in the 

 literature: Coral spots on carmine background 

 are not due to chromosome loss since chromo- 

 some numbers in variegated and self-coral petals 

 of the same plant are identical; furthermore, 

 coral branches on a variegated plant produce 

 variegated test-cross progeny. Certain similarities 

 with v-type position effect can be noted, but 

 structural rearrangement is not required for 

 coral spotting to occur. Paramutation is obli- 

 gatory in certain heterozygotes of maize and the 

 changed allele is passed on to the progeny while 

 carmine-coral variegation seems to occur hapha- 

 zardly and the changed form is not transmitted 

 sexually, as stated. As yet incomplete genetic 

 studies indicate that a single factor, co v , from 

 N. otophora is involved which is dominant over 

 coral (co) of N. tabacum and which thus far 

 appears to be autonomous since no controlling 

 element could be separated by backcrossing and 

 stable carmine types could not be obtained. One 

 may hypothesize that there exists in N. tabacum 

 (chromosomes or cytoplasm) a repressor element 

 which at times inactivates co v in somatic cells. 

 During the reproductive cycle the potentiality of 

 co v for pigment formation is restored. 



4.27. Studies on Amylase in Drosophila meianogaster 

 by Agar-electrophoresis. Hideo Kikkawa and 

 Zenichi Ogita (Osaka, Japan). 



It has been found by the senior author (1960) 

 that the amylase activity in D. meianogaster is 

 controlled by a semidominant gene located at 



about 80 on the second chromosome. However, 

 the amylase activities differ from one another 

 according to the strains used. 



By using an agar-electrophoretic method 

 modified by the junior author, amylases in 

 various strains have been analysed. Seven amy- 

 lase bands were found as a whole on a zymogram. 

 But each strain showed a characteristic pattern in 

 amylase bands. For instance, Amy + strain showed 

 only one clear band (No. 1), whereas Amy" 

 strain showed two clear bands (No. 2 and No. 6). 



Fi individuals between any two strains which 

 showed different patterns in amylase bands, gave 

 a mixed type of parental patterns on a zymogram. 

 No additional band has been detected except the 

 parental ones. This result suggests that each 

 allelic gene produces its own amylase protein in 

 the cytoplasm, and also that no hybridization 

 occurs between components of the enzyme 

 proteins. 



4.28. Studies on the Genetic Control of Xanthine 

 Dehydrogenase in Drosophila meianogaster. 

 R. P. Kernaghan and A. Chovnick (Storrs, 

 U.S.A.). 



Xanthine dehydrogenase activity in Drosophila 

 meianogaster is controlled by at least three 

 functional units (ry, ma-1, and bz). Mutation in 

 any of these units produces a pleiotropic phe- 

 notype including absence of xanthine dehydro- 

 genase activity (Forrest, Classman, and Mitchell, 

 1956; Glassman and Mitchell, 1956; Glassman 

 and Pinkerton, 1960; Hadorn and Schwinck, 

 1956; Nawa, Taira, and Sakaguchi, 1958). The 

 inactivation of antibody specific to xanthine 

 dehydrogenase suggests that ma-1 1 contains 

 greater amounts of cross reacting material 

 (CRM) than ry' 2 (Glassman, and Mitchell, 1958). 

 The data on the fine structural organization of 

 rosy (Chovnick et ah, 1962) and the description 

 of ma-1 2 (Schaiet, 1962), which complements 

 neither ma-1 1 nor bz, requires a re-examination 

 of the CRM question. 



Extracts of wild type and mutant stocks were 

 partially purified with Sephadex. Enzyme ac- 

 tivity was determined as the increase in optical 

 density at 395 mu due to the reduction of added 

 thionicotinamide — adenine dinucleotide mediat- 

 ed by the conversion of 2-amino, 4 hydroxpteri- 

 dine to isoxanthopterin. Mutant extracts were 

 tested for their ability to remove specific anti- 

 enzyme activity from antibody preparations. 

 Ma-1 x and bz are positive while ma-1 2 is negative 

 with respect to CRM activity. Several rosy 

 mutants (ry 1 , ry 2 , ry 8 , ry 9 , and ry 23 ), were sub- 

 stantially negative. An anti-ma- 1 1 antibody 



45 



