The Genetic Control of Mutability 223 



Sandler, L., Hiraizumi, Y., and Sandler, I., "Meiotic Drive in Natural Populations of Dro- 

 sophila Melanogaster. I. The Cytogenetic Basis of Segregation-Distortion," Ge- 

 netics, 44:233-250, 1959. 



van Schaik, N. W., and Brink, R. A., "Transpositions of Modulator, a Modifier of the 

 Variegated Pericarp Allele in Maize," Genetics, 44:725-738, 1959. 



QUESTIONS FOR DISCUSSION 



25.1. How is the precision of the mitotic and meiotic processes related to the mutability of 

 the genetic material? 



25.2. Defend the statement that meiosis and mitosis are not intrinsic properties of genes. 



25.3. If whole genome changes represent a class of mutation, should the changes in ploidy 

 which occur in gametogenesis and fertilization be considered mutations? Why? 



25.4. Does Dissociation itself provide evidence for the genetic control of mutability? Ex- 

 plain. 



25.5. What evidence can you present that variegation is not due to the effect of a single 

 pair of genes, one of whose alleles is unstable? 



25.6. Could you detect the transposition of a transposed Modulator to a locus near f"? 

 Explain. 



25.7. Why does a light variegated individual of maize, that has a transposed Modulator on 

 the same chromosome as P"^ Mp, produce more than one quarter of F, offspring that 

 are lights and less than this that are mediums, when this individual is backcrossed to 

 nonred (/»" P")? 



25.8. Could Modulatorlike genes be the cause of relatively rare "mutants" of amorphic, 

 hypomorphic, or neomorphic types? What is the basts for your opinion? 



