272 



CELL HEREDITY 



Narrowed lumen 

 of trachea 



Anomaly of cartilage 



Abnormal sternum 

 Thickened ribs 



Fixation of thorax 

 in inspiration 



Slight changes in 

 larynx, nose, and 

 other cartilages 



Kyphosis 



Abnormal situs of 

 thoracic viscera 



Retardation of 

 lung development 



Spur of deltoid 

 ridge of humerus 



Compensating 



increase of 



red cells 



and Hi 



Slow 

 suffocation 



Coma 

 Exposure 

 Inanation 



Increased 



resistance in 



pulmonary 



circulation 



Compensatory 



hypertrophy of 



right ventricle 



of heart 



Decompensation 



Capillary 



pulmonary 



haemorrhages 



DEATH 



General 



arrest of 



development 



Blunt 

 snout 



Faulty 

 occlusion 

 of incisors 



Difficulties 

 in feeding 



Blocked 

 nostrils 



Inability 

 to suck 



Starvation 



FIGURE 10.1. Pedigree of causes of death from a single lethal gene in the rat from 

 Grijneberg, 1947, Animal Genetics and Medicine, New York, Hoeberl. 



pigment is present in the flowers of BB and Bb plants, while in bb plants, 

 the flowers are ivory or white. In the snapdragon, plants of the genetic 

 constitution XY or Vi/ have yellow flowers containing tw o antho.xanthins, 

 both of which are absent (or undetectable) in white-flowered plants 

 w hich are ijy. 



In the primrose, evidently a single gene mutation has resulted in the 

 alteration or loss of a single pigment. Specific biochemical differences 

 between wild-type and mutant organisms have been demonstrated in 

 many isolated instances in higher plants and animals. More frequently. 

 however, the analysis has indicated that a single gene mutation has 

 given rise to more than one change in the phenotvpe. This phenomenon, 

 called pleiutwpism, is a reflection of the highlv integrated state of 

 metabolic and developmental pathways. The snapdragon example, in 



