CHAPTER II 



THE INHERITANCE OF 

 BIOCHEMICAL CHARACTERISTICS 



I. CONTROL OF BIOCHEMICAL CHARACTERISTICS BY GENES 



Beadle has expressed in the following terms the generally held views today 

 on the transmission of biochemical characteristics : 



"In order to exist as such, genes obviously must be capable of inducing 

 the formation of exact copies of themselves. ... In addition to catalysing 

 formation of more units like themselves, genes in general have hetero- 

 catalytic properties, that is they catalyse the formation of other substances. 

 ... In determining the specific chemical and perhaps physical configuration 

 of protein molecules, genes directly determine enzyme specificities and 

 thereby control in a primary way enzymatic synthesis and other chemical 

 reactions in the organism. ..." 



The colour of the fruit of the tomato Lycopersicon esculentum results from 

 the presence of a series of carotenoids whose existence depends on at least 

 three genes (T, R, B,). As far as the two genes T and R are concerned, 

 Table XVIII shows the carotenoid pattern in four pure strains of Lyco- 

 persicon of the four genotypes RT, Rt, rT and rt. 



Table XVIII 



The carotene content of four strains of tomato 



(Mackinney and Jenkins, 1952) 



304 



