Questions and Problems 185 



b and d, 40 per cent. What percentage of crossing over would be expected 

 between a and dl 



23. If a new gene, e, was found and if it showed 50 per cent crossing 

 over with all four of the genes mentioned in question 22, could you state 

 with certainty that it was not on the same chromosome with the other 

 genes? 



24. If linkage was complete in both sexes (as it is in the male Dro- 

 sophila), could you plot the genes on the chromosomes? 



