The Molecular Basis of Mutation 403 



31.8. How permanent must a change in a nucleotide be before it can be considered 

 a mutant? 



31.9. Would you consider the substitution of P 1 -' for P in the phosphate of a nucleo- 

 tide a mutation? Why? 



31.10. What do you think of the statement that the only way we have of detecting 

 changes in individual genes is by the phenotypic changes they produce? 



31.11. E. coli contains a locus capable of conferring resistance to c/>Tl irradiated with 

 ultraviolet light. Substituting 5-bromodeoxyuridine for the thymidine in the 

 phage, however, removes this protection. What do you suppose is the product 

 and mechanism of action of the bacterial locus involved? 



