INHERITANCE OF ALLERGY 



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line. Following out this line of reasoning and assuming that there is a 

 specific modifying gene for each allergy, we would expect these dominant 

 modifiers to cause new allergies in a fair percentage of the children. If the 

 negative parent were heterozygous for the modifying gene, only half the 

 children would have the new allergy. In any event we should never expect 

 complete dominance, since we have shown that the dominance is variable. 

 However, the new combinations in the F x are of various kinds; one indi- 

 vidual having one new allergy, another a second, and still others having 

 different combinations of them. Sometimes only a small percentage of 

 the progeny show the dominance of a particular type of allergy, and in other 



TABLE 1* 



*Note: A— asthma; B— bronchitis; E— Eczema; H— hay fever; M— migraine; 

 U — urticaria. 



cases the same allergy that has been shown in similar crosses to act as a 

 dominant does not appear in the Fi although it may be present in the parent. 

 As this chart shows, the allergy of the parent may not appear at all in the 

 Fi, although in other cases this same allergy acts as a dominant. Since 

 the person from the negative line, after crossing with the allergic line, pro- 

 duces various combinations of allergies, some present in the allergic parent, 

 some present in members of the family of the allergic parent, and others 

 entirely new in the family, and since these allergies, old and new to the 

 family, do not appear in any regular proportion, it seems illogical to con- 

 sider that the negative line has brought in modifying factors for a new set 

 of allergies. If such were the case these new allergies, being dominant as 

 we have shown, should appear in a fairly large proportion of the F x , a result 

 not found to be true. 



