Mendel's Law % 39 



typically and phenotypically, that is, with the same 

 germinal constitution and the same appearance. By in- 

 breeding these F! individuals, it will be seen that four 

 kinds of gametes are involved. Crossing these four kinds 

 of gametes the resulting combinations are indicated in 

 fig. 5 . The resultjs four phenotypes. as follows : nos. i, 2} 

 3, 4, 5, 77~<^~K> 13 are tall smooth individuals; n 

 15 are dwarf smooth; nos. 6 K 8, 14 are tall wrinkled; 

 no. 1 6 is dwarf wrinkled* Tus_js_Jiei 



It will be noticed that nos. i^ 6, n, 16 

 zygotes and therefore will breed true; but the Test are 

 heterozygotes, either for ^one pair of characters or for 

 both, and these would split into various types upon 

 further breeding. 



The next step is the trihybrid ratio. MENDEL found 

 yellow seeds dominant over green seeds, and if thispair 

 of characters is included with those used above the tri- 

 hybrid result can be observed. The experiment would 

 consist in crossing tall, smooth, yellow individuals 

 with dwarf, wrinkled, green individuals; and it is 

 obvious that the hybrid progeny would all be tall, 

 smooth, yellow, since these three characters are domi- 

 nant. Inbreeding the hybrids gives the following 

 result in the_F 2 generation : 27j:all smooth yellow, o_talL 

 smooth green, g^tall wrinkled yellowy^ dwarf 



yellow, 3 tall wrinkled greeai^^ x dwarf smooth green, 

 3 ^iwarf^wmikled yellowg)i dwarf wrinkled 

 The tflbybrid ratio therefore is .27:0:0:0:3 



This involves 64 individuals and 8 phenotypes. 



1. JOHANNSEN, W., Elemente der exakten Erblichkeitslehre. 

 Jena. 1909. 



2. MENDEL, G., Versuche iiber Pflanzen-Hybriden. Verb. Naturf. 

 Vereins in Briinn 4: 1865. 



