CHAPTER VI 



THE CORRESPONDENCE BETWEEN THE 



DISTRIBUTION OF THE CHROMOSOMES 



AND OF THE GENETIC FACTORS 



Attention has been called to the fact that paired 

 factors are distributed in the same way as are 

 homologous chromosomes, and that factors which 

 are assorted independently are distributed in the 

 same way as non-homologous chromosomes. In 

 proof of the latter point there is Wilson's evidence 

 for a Metapodius with three homologous m-chromo- 

 somes. It was found that the extra m goes to the 

 gamete that receives X as often as to the other 

 gamete. Miss Carothers describes a somewhat 

 similar case in certain grasshoppers, in which the 

 distribution of a pair of unequal chromosomes is 

 independent of the distribution of the X chromo- 

 some. Not only are the pairs of factors assorted 

 independently, as are the chromosomes, but in 

 Drosophila, where the number of independently 

 assorting groups of factors has been determined, it 

 has been found that the number is identical with the 

 number of chromosome pairs. Moreover, even the 

 relative sizes of the groups both as determined by 

 the number of factors they contain and by the fre- 

 quency of crossing over within them are the same 



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