The Possible, Combinations ProdiLcwL by fertilisation in an, 

 Organism the Cittscf which Contain Four Chromosomes. 



TTie Four- 



PcisU'stc the Qamefes, 



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Contain any cf tk&Jcll/cwiny Combinations. 



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Wke,rv fertilisation; tallies place-, tu-o Q&me tts J"u,sc^. Tti&Joilcwu-Lg Combination's aj'&f> 

 and are. probnkte ct,cccrd(,ng Co th.ofre*fu*ncy tvMv tvhicA ttwy ecc4ir(/n/tti,cuiara,m/. 



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FlG. 16. The diagram shows that in an organism the cells of which contain four 

 chromosomes, six different combinations of two chromosomes are equally pro- 

 bable in the gametes. It also shows that in fertilisation these pairs contained 

 in the gametes may be combined in thirty-six different ways. In six of these 

 the chromosomes are the same as in the parent organism. Thus in an organism, 

 the cells of which contain four chromosomes, there is one chance in six that the 

 original combination will be reproduced in the offspring, and this only when 

 it is assumed that the chromosomes in both parents are the same. In man, 

 where there are thirty-two chromosomes in a cell, the number of different sets 

 of sixteen is enormously large, and the chance of the original combination being 

 reproduced in fertilisation is only one in over six hundred million. 



