120 GENETICS 



there would result over a million possible kinds of 

 offspring among the hybrids of the second filial 

 generation, (3+l) 10 =l,048,576. 



From the foregoing it is apparent that in practical 

 breeding the only hope lies in dealing with not more 

 than one or two characters at a time. Since unit 

 characters usually behave independently of each other, 

 one may breed for a single character until it is segre- 

 gated out in a homozygous, that is pure, condition, 

 and then in the same way obtain a second character, a 

 third, and so on. 



This is not difficult if the character sought is a 

 recessive for, in that case it is already homozygous or 

 pure and consequently appears. When a character is 

 dominant it takes longer to determine whether the 

 individual is heterozygous (hybrid) or homozygous 

 (pure). 



14. CONCLUSION 



The Mendelian method is an attempt to analyze the 

 behavior of a particular characteristic in heredity 

 rather than to get at the lump performance of the in- 

 dividual as a whole. Herein lies the scientific control of 

 heredity which the trinity of Mendelian principles 

 namely, independent unit characters, segregation, and 

 dominance, has placed in human hands. Following this 

 method there can be obtained in a few generations of 

 properly directed crosses, combinations of characters 

 united in one strain that formerly were never obtained 

 at all or were only hit upon by the merest chance at 

 long intervals. 



