388 CHARACTER EXPRESSION OF GENES 



of plants in which there are six shades of red besides 

 white. Without going into detail it may be said that 

 this result depends on the fact that the red grandparent 

 has three pairs of genes for red and all are practically 

 equivalent. They reconibine in the second generation so 

 that some plants have 6 red genes, some 5, some 4, some 

 3, some 2, some 1, and some none, thereby giving rise to 

 as many color types. The way this works out is shown 

 in the accompanying Punnett square (Fig. 115). 



Fio. 115. — The Ft of a Certain WTieat Cross where the red parent 

 (RREEDD) diflFers from the white one (rreedd) in respect to three 

 separate and independent pairs of genes, all of which are capable 

 of producing some red color. The F| is about half as red as the red 

 parent. When this half-red hybrid (RrEeDd) is self-iwllinated it pro- 

 duces the genot>TX» combinations shown in the Punnett square. 

 Note that since each of the genes R, E, and D are equivalent and 

 their eflfects cumulative, there will be 1 plant with 6 doses of red, 

 6 plants with 5 doses, 15 with 4 doses, 20 with 3 doses, 16 with 2 

 doses, 6 with 1 dose, and 1 with no red, i.e. white. 



