226 BOTANY: PRINCIPLES AND PROBLEMS 



ence between these two colors is due to a single factor. If a plant 

 homozygous for white is crossed with a plant homozygous for yellow 

 fruit color, what will be the appearance of the Fi generation? of the 

 F2 generation derived by self fertiUzing one of these Fi ijlants? What 

 proportion of the white-fruited F2 plants will breed true if self-fertilized? 



579. What will be the fruit color of the plants produced by crossing 

 one of the Fi individuals, mentioned in Question 578, with its yellow- 

 fruited parent? with its white-fruited parent? 



580. Let the factor for white fruit color in the squash be represented 

 by W and that for yellow by Y. What kind of gametes, as far as 

 their factors for fruit color are concerned, will be produced by plants 

 having the following genotypes: WW, WY, YY? 



581. What gametes will be produced by the plants involved in 

 the four following crosses; and what will be the fruit color of the offspring 

 from each cross: 



WY X YY; WW X WY; YY X WW; WY X WY? 



582. A white-fruited squash plant when crossed with a yellow- 

 fruited one produces offspring about half of which are white and half 

 yellow in fruit color. What are the genotypes of the parent plants? 



583. If the white-fruited parent plant in the preceding question is 

 self-fertilized, what will be the fruit color of its offspring? 



584. If this same white-fruited parent is crossed with one of its white- 

 fruited offspring mentioned in Question 582, what chance is there of 

 obtaining from this cross a yellow-fruited plant? 



585. Two white-fruited squash plants when crossed produce about 

 three-fourths white and one-fourth yellow offspring. What are the 

 genotypes of these two parents, as to fruit color? What will each pro- 

 duce if crossed with a yellow-fruited plant? 



586. A cross between a white-fruited and a yellow-fruited squash 

 plant produces offspring all of which have white fruits. If two of these 

 F\ plants are crossed together, what will be the fruit color of Uidr 

 offspring? 



'Note. — In Four-o'clock flowers, red flower color is incompletely domi- 

 nant over white, the hybrids being pink-flowered. 



587. If a red-flowered Four-o'clock plant is crossed with a white- 

 flowered one, what will be the flower color of the Fi? of the F2? of 

 the Fi crossed back on the red-flowered parent? of the Fi crossed back 

 on the white-flowered parent? 



