GENERAL RELATIONS IN INHERITANCE 30I 



same and nearly homozygotic, members of the same family 

 are genetically closely alike. If the two parents differ greatly 

 in their genes and are in a high degree heterozygotic, mem- 

 bers of the same family are genetically very diverse, having 

 very different combinations of genes and characteristics. 



Relation of Gene Recombinations to the Transformation 

 of Organisms in the Passage of Generations 



The recombinations of genes and of characteristics that 

 we have been considering have important consequences in 

 transforming organisms as time passes. There are three 

 main types of such consequences : 



First, in this way there are produced combinations of 

 genes, and therefore of characteristics, that have not before 

 existed. 



Second, in this way single qualities, powers and dimen- 

 sions may be increased beyond the degree in which they 

 formerly existed. 



Third, as a result of the recombinations of genes, char- 

 acteristics may appear in the descendants that have not oc- 

 curred in the ancestors. 



These three types of consequences we may consider 

 separately: 



/. As we have already seen, by biparental reproduction, 

 any quality or peculiarity of any individual or stock may 

 become combined with any characteristics of any other indi- 

 vidual or stock with which it can unite in parenthood. In 

 this way may be produced combinations of characteristics 

 that have never before been brought together. Illustrations 

 of such changes have been given in preceding paragraphs. 

 Such recombinations play a great role in relation to the 

 fitness or adaptiveness of organisms. Thus, one stock may 

 have strength and agility, but also poor sight and hearing. 

 Another may have acute senses, but be weak and slow. By 



