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SS * 



Individuals of pure breed can produce only one com- 

 bination of chromosomes in their gametes 



IQ 



If they are not crossed, their gametes can result only 

 in pure individuals, having the same combinations of 

 recessive and dominant traits as the parents 



I 



When gametes from two strains combine, the zygote 

 receives chromosomes of different kinds 



Pure gametes can combine in two different ways: 



Parent type A eggs X B sperms 

 Parent type B eggs X A sperms 



The zygotes have the same chromosome combination 

 in either case, and in all the hybrid progeny each trait 

 is dominant in appearance 



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When hybrid individuals form germ cells, the pa- 

 rental chromosomes of each pair become separated in 

 the reduction division 



Four types of eggs and four types of sperms make 

 sixteen different zygotes possible 



The segregation agrees perfectly with the results of 

 Mendel's experiments: 



12 tall : 4 not-tall 



12 smooth : 4 not- smooth 



In appearance, they are 



9 TS : 3 Ts : 3 ts : 1 ts 



CHROMOSOME BEHAVIOR AND INHERITANCE 



In this type of succession, how many individuals resembling a grandparent can 

 transmit both the latter's distinctive traits? 



