288 



INTRODUCTION TO CYTOLOGY 



r^ 



T T 



PAREMT5 



r^ 



XX 



/\ 



/\ 



00 00 



CAMtTLS 



F, 



Tt 



T t 



GAMtTES 



/ \ /\ 



0000 



Fig. 165. — A typical example of simple Mendelian heredity. In a cross between pure 

 tall and pure dwarf peas, tallness is dominant over dwarfness in the first filial generation 

 (Fi). In the second filial generation (Fi) tall plants and dwarfs occur in the ratio 3:1. 

 At the right is shown the distribution of factors for tallness (T) and dwarfness (t) through 

 these generations. The letters T and t may also be considered as representing a homolo- 

 gous pair of chromosomes. 



