Hybridization and Selection 301 



PROBLEMS 



Whj 



at kind of variations are brought about by cultivating and by adding 

 fertilizers to the soil? 



2. What kind of variations appear to have been most important in the pro- 



duction of the different kinds of plants that occur on the earth? 



3. How would you attempt to secure a new mutant? 



4. Why are there fewer variations when plants are propagated vegetatively 



than when reproduced b}^ seed ? 



5. Corn is propagated by seeds. Plow would you plant and care for a corn 



seed plot in order to secure loo per cent hybrid seed? 



6. If a plant has three pairs of different chromosomes, how many different 



kinds of sperms and eggs can it produce? 



7. If you were to cross a tall white-flowered pea with a dwarf purple-flowered 



pea, what would you obtain in the hybrid or Fi generation ? What per 

 cent or fraction of the Fo generation would be dwarf white-flowered peas> 

 What fraction of the Fo generation would be tall purple-flowered peas? 

 What fraction of these tall purple-flowered peas would be homozygous 

 for both characters? What per cent of the dwarf white-flowered peas 

 would be homozygous for both characters? 

 I. If you were to cross a pure tall purple-flowered pea with smooth seeds with a 

 pure dwarf white-flowered pea with wrinkled seeds, what chance would 

 you have of obtaining a pure tall white-flowered pea with wrinkled seeds 

 in the F2 generation? 



