XII THE CHROMOSOME THEORY 143 



went to form the F^ female, Further, if we suppose 

 that the point of junction may occur with equal 



Fig. 42. 



Diagram illustrating the process of " crossing-over." between paired chromosomes'. 

 When the point of junction is situated as in A or .S, the gametes formed are 

 "non-crossover "gametes in respect of the factors G and N. When the point of 

 junction is situated as in C, the gametes formed are "cross-over" gametes in 

 respect of G and N, ^ 



likelihood at any point along the chromosomes it 

 is clear that the chance of two factors becoming 



o 



