ELABORATIONS OF MENDEL S LAW 



351 



Case of Paired Dominants and Paired Recessives. — A 



beautiful experiment was made by crossing a variety of pea with. 

 Round seeds and Yellow albumen (a pair of dominant characters) 

 with another variety with angular seeds and green albumen (a pair 

 of recessive characters). The result was offspring all like the 

 dominant parent. These hybrids were inbred, and the results 

 were some Round, and Yellow, some Round and green, some angular 

 and Yellow, some angular and green. (The dominants are 

 represented by italics and capitals.) 



RY ag 



RY(ag) 

 Suppose the germ-cells segregate into the four possible kinds (say 

 100 of each) : 



(1) 100 RY 



(2) 100 Rg 



(3) 100 aY 



(4) 100 ag 



^'J 



which in inbreeding unite with four similar 

 kinds ........ 



fRY 100 

 ' Rg 100 

 I aY loa 

 as 100 



What are the possible combinations (it being understood that 

 form and colour represent a i>aiY of characters — i.e. RR, Ra, etc., 

 are impossible). 



(I) 

 25 RY X 25 RY = 25 RY 



2sRYx 25 Rg =25RY(g) 



25 RY X 25 aY = 25 RY (a) 



25 RY X 25 ag = 25 RY (ag) 



100 RY 



(2) 

 25Rgx 25RY=25RY(g) 

 25 Rg X 25 Rg = 25 Rg 

 25 Rg X 25 aY = 25 RY (ag) 

 25 Rg X 25 ag = 25 Rg (a) 



(3) 



25 aY X 25 RY = 25 RY (a) 

 25 aY X 25 Rg = 25 RY (ag) 

 25 aY X 25 aY = 25 aY 

 25 aY X 25 ag = 25 aY (g) 



= 50 RY + 50 Rg 



(4) 

 25 ag X 25 RY ^ 25 RY (ag) 

 25 ag X 25 Rg = 25 Rg (a) 

 25 ag X 25 aY =25 aY(g) 

 25 ag X 25 ag = 25 ag 



= 25 RY + 25 Rg + 

 25 aY + 25 ag 



= 50 RY + 50 aY 



The characters in brackets may be disregarded, since they behave as 

 recessives to their correspondents. Thus the total is — 



225 RY + 75 Rg + 75 aY + 25 ag 

 or 9 RY + 3 Rg + 3 aY -r i ag 



This actually corresponds with results obtained. 



