MENDELIAN INHERITANCE 



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allelomorphs which are separated from one another during the 

 maturation divisions (Fig. 90). Two kinds of spermatozoa 

 and two kinds of eggs result. On self-fertilization one kind 

 of sperm may unite with an egg containing its like kind, or it 

 may unite with an egg containing its allelomorph. Or the other 



o 



FIG. 97. Diagram illustrating Mendelian inheritance when two character- 

 istics are involved. A yellow-round and a green-wrinkled pea are crossed. The 

 FI generation gives only yellow and round peas, these being dominant over green 

 and wrinkled. These when inter-bred segregate out in the proportion of 9 : 3 : 3 :i. 

 (From Morgan.) 



sperm may unite with its allelomorph or its like, the result 

 would be the Mendelian proportion of three to one. 



B. HEREDITY OF Two PAIRS or CHARACTERS. Mendel 

 worked out the principles of heredity in cases where two or 

 more pairs of characters are involved and found the same under- 

 lying principles of dominance and segregation as in the case of a 

 single pair. He crossed a pea producing yellow and round seeds, 

 with one producing green and wrinkled seeds. The Fi genera- 

 tion or hybrid seeds were yellow and round, showing that the 



