THE GENE AND BIOCHEMISTRY 



Foiling (14) and Penrose (35) have shown that the genetically 

 determined failure to oxidize phenylpyruvic acid in man is invariably 

 associated with subnormal mentality. Here again there appears to be 

 an intimate relation between a particular gene and a specific chemical 

 reaction. Because of its obvious importance to an understanding of 

 the mechanisms underlying mental processes, this case is of particular 

 interest. It is of course related metabolically to alcaptonuria in so far 

 as phenylalanine is concerned in both. Other abnormalities in 

 phenylalanine-tyrosine metabolism are also known (15,19). 



Most remarkable progress has recently been made in under- 

 standing the genetic and chemical mechanisms of sex determination 

 and differentiation in the green alga, Chlamydomonas, by Moewus, 

 Kuhn, and co-workers. From the carotenoid pigment, protocrocin, 

 there is derived through cleavage the motility hormone, crocin, and a 

 female-determining hormone known as gynotermone. This cleavage 

 is known to be genetically controlled. In genetically male individuals 

 gynotermone is hydrolyzed to a male-determining hormone known as 

 androtermone. Under the direction of specific genes the cis and trans 

 forms of the motility hormone, crocin, are converted into the corre- 

 sponding cis and trans dimethyl esters of crocetin. In various specific 

 mixtures, these serve as gamones, i. e., they render individuals of the 

 specific genetic constitutions capable of conjugation. The relations 

 between genes and chemical reactions disclosed by this work support 

 the thesis that genes act in directing specific processes. The work on 

 Chlamydomonas is so spectacular and its importance so great that inde- 

 pendent confirmation is desirable (see 7,28,41). 



The splitting of specific di- and trisaccharides by yeasts is under 

 genetic control, as shown by Winge and Laustsen (54) and Lindegren, 

 Spiegelman, and Lindegren (25). It appears that the genes concerned 

 determine whether or not specific enzymes are present in active form. 

 Somewhat similar situations are known in the rabbit, where Sawin 

 and Glick (37) have shown that the activity of the enzyme, atropine 

 esterase, is dependent on the presence of the normal allele of a par- 

 ticular gene, and in white clover, where an enzyme responsible for 

 hydrolysis of specific cyanogenetic glucosides is known to show a similar 

 dependence on a gene (2,9). 



In the bread mold, Neiirospora, Srb and Horowitz (44) have 

 shown that there is present an ornithine cycle essentially similar to 



