Dominant cold paralytic mutations on the X‐chromosome of Drosophila melanogaster

Six new cold paralytic behavioural mutations on the X‐chromosome of Drosophila melanogaster are reported. All mutations map to a position of 1.7 map units to the left of f where also a previously found cold paralytic mutant has been located. On the basis of complementation tests and behavioural studies the new mutants were all considered to be mutations of the same locus as the previously found cold paralytic mutant, Ocd *, and therefore called Ocd ks‐2 to Ocd ks‐7 . Only minor differences were found in the cold paralytic behaviour of Ocd ks‐2 to Ocd ks‐6 when compared to Ocd ks‐1 . The critical temperature of Ocd ks‐7 was found to be 2°C lower than for the other mutants. The Arrhenius activation energy of succinate‐cytochrome c reductase exhibited a change at about 18°C in mitochondria from mutants Ocd ks‐2 to Ocd ks‐6 . In Ocd ks‐7 this change had been shifted to 16°C. These data confirm the correlation between the cold paralysis and the change in activation energy which has previously been established for Ocd ks‐1 .