MENDELISM 9 



This is the first of Mendel's results, and I hope it has 

 been made clear to you. It forms the foundation of what 

 follows. 



We require some short formula which will express the 

 fact of dominance. If we are considering stature, we can 

 employ the following formula — 



Tall x Dwarf (parents) 



Tall (offspring) 



which means that when a tall plant is crossed with a dwarf 

 all the offspring are tall. 



But it is desirable to use some formula which will 

 express the fact of dominance of any character, and this 

 can be done by using D to represent a dominant and R to 

 represent a recessive ; thus — 



D x R 



D 



You see this applies not only to stature, but to any of 



the characters above mentioned. 



Another formula very commonly employed is the 



following — 



• x o 



where the black circle stands for the dominant, and the 

 white circle represents the recessive. 



Both the diagrams show that the offspring of certain 

 crosses resemble one of the parents, and not the other. 

 The parent which is like the offspring is the dominant 

 parent. 



The next step was to breed from these hybrid plants 

 by allowing them to become self-fertilized (the usual method 

 of reproduction in peas). Mendel found that the two 



