Section 10 — Developmental Genetics 



exist, with none or one dominants; males would 

 belong to three genotypes, with two, three or 

 four dominants. The variability of sex iatio and 

 the results of different crosses are thus explained 

 by a relatively simple oligogenic hypothesis, 

 without introduction of modifying genes, 

 cytoplasmic factors, etc., as has been implied by 

 other authors in other species. The selective 

 value of this situation versus a clear cut 1 : 1 

 mechanism is investigated and discussed. 



10.55. (D) Genetic Analysis of the True Slime Mould, 

 Physarum polycephalum. Jennifer Dee (Lon- 

 don, Great Britain). 



The true slime mould (Myxomycete) Physarum 

 polycephalum undergoes simple morphogenetic 

 changes during its life-cycle and passes through 



a uninucleate phase and an acellular multinu- 

 cleate phase, either of which can be indefinitely 

 prolonged in culture. It should be a highly 

 suitable organism in which to combine genetical 

 and biochemical approaches to the problems of 

 morphogenesis. Biochemical investigations are 

 becoming advanced, but very little genetic 

 analysis has been done. The demonstration 

 illustrates an attempt to develop genetic analysis 

 of P. polycephalum. 



Simple techniques are shown for culturing the 

 organism through its life-cycle in two-membered 

 culture. Stages of the life-cycle are illustrated by 

 living cultures or photographs. The uninucleate 

 phase ("amoebae") can be handled by the usual 

 techniques of microbial genetics including 

 plating, which is demonstrated. The mating-type 

 system, methods of isolation of genetic markers 

 and the results of a cross showing recombination 

 between genetic markers are also described. 



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