Heredity 



185 



RP 



SPERMATOZOA 

 Rp rP 



rp 



RP 



Rp 



rP 



rp 



Diagram to illustrate the nature of the F 2 generation from the cross of 

 rose comb X pea comb. (After Punnett.) 



All the resulting zygotes containing both rose and pea 

 (RP) will be walnut ; those containing rose only (R) and 

 not pea (p) will be rose and those containing pea only (P) 

 and not rose (r) will be pea-combed. But all individuals 

 containing neither rose nor pea will have single combs. 

 This was found to be a pure recessive and to breed true. 

 The character of singleness seems to underlie all the types 

 of comb and appears whenever allowed to do so by the 

 absence of something representing the other kinds. 



Mendelian inheritance of color. Colors of plants or 

 animals are generally very complex and often consist of 

 many units of different kinds. Very rarely a certain color 

 may be said to be due to a single unit acting alone. A 

 knowledge of the kinds of color and the constitution of 

 each is necessary to understand their inheritance. 



