Section 15 — Human Genetics 



PKU case may account, at least in part, for 

 the higher frequency we are encountering with 

 this method. This possibility will be discussed. 



Work supported by grants from the National 

 Association for Retarded Children, Association 

 for Aid for Crippled Children, the National 

 Foundation, United States Public Health Ser- 

 vice, Grant Number B-1960, and the Children's 

 Bureau. 



1 . Proc . London Conf. Scientific Study of Mental 

 Deficiency, 1962, Vol. 2, pp. 672-677. 



2. New Eng. J. Med. 267, 1208, 1962. 



15.67. Pharmacogenetic Aspects of Taste. Roland 

 Fischer, Frances Griffin (Columbus, U.S.A.) 

 and A. R. Kaplan (Cleveland, U.S.A.). 



parents of children affected with Down's syn- 

 drome. In the maternal sample the antimode, 

 dividing the age of younger mothers from that 

 of older ones, coincides with the threshold anti- 

 mode dividing tasters from ("non"-)tasters of 

 PROP. In addition, all but one of the fathers in 

 the sample can be characterized as markedly 

 insensitive ("non"-)tasters of PROP. 



1. Fischer, R., Griffin, F., and Mead, E.: 

 Med. exptl. 61, 177 (1962). 



2. For taste testing procedure and criteria, 

 see Fischer, R. and Griffin, F. : Proc. Hlrd 



World Congr. Psychiat. June 1961, Montreal, 

 Vol. 1, p. 542). 



3. Nature 195, 362 (1962). 



4. Nature 179, 1074(1957). 



Very insensitive ("non"-)tasters of HN-c = S 

 type goitrogens, such as 6-n-propylthiouracil 

 (PROP), are also insensitive tasters( 1 ) of an 

 apparently unlimited series of chemically un- 

 related compounds* 2 ). Differential taste pro- 

 files for 34 such compounds, mainly drugs, 

 will be presented and the stereospecificity of 

 chemoreception described. Sensitive tasters of 

 PROP can taste 8-times less 1 -quinine (sulfate, 

 chloride, or free base) — concentrationwise — 

 than d-quinine, whereas the reverse is true only 

 for quinine chloride in the case of very insensitive 

 ("non"-)tasters of PROP who constitute about 

 10-12 percent of a Caucasian population. Taste 

 testing practice, extending for months, with 

 mixtures of PROP and quinine — under experi- 

 mental conditions described by Rubin, Griffin, 

 and Fischer( 3 ) — can abolish this difference and 

 make a "learned" taster from a very insensitive 

 ("non"-) taster. This phenomenon can be related 

 to Beckett and Anderson's model of "footprint- 

 ing" on stereoselective adsorbents. ( 4 ) 



If the human oral cavity is regarded as a 

 pharmacological preparation /'// situ, taste 

 thresholds for drugs — alone or in mixture — 

 and drug activity can both be treated as ana- 

 logous pharmacological responses. By plotting 

 the taste thresholds of certain molar ratios of 

 two drugs — in subthreshold concentrations — 

 isoboles can be obtained which may be inter- 

 preted as a characteristic systemic response of a 

 particular subject to a binary mixture of drugs. 

 Sensitive and insensitive taster (drug responders) 

 appear to produce different isoboles for the 

 same pair of drugs. 



Another pharmacogenetic aspect of taste is 

 illustrated by the following observation in 40 



15.68. Reexamination of Genetic Aspects of Taste 

 Thresholds for Thiourea-type Compounds. 



Arnold R. Kaplan, Wilma Powell, Ro- 

 land Fischer and Roger Marsters (Cleve- 

 land, U.S.A.). 



Monozygotic and same-sex dizygotic twins 

 have been classified according to their taste 

 thresholds for 6-n-propylthiouracil (PROP) and 

 various other compounds. Zygosity determina- 

 tions are based on combinations of morphologic 

 characteristics and blood types. 



A modified Harris-Kalmus testing procedure 

 has been employed — using distilled water for 

 the serial dilutions, placebo, and between- 

 sampling mouth rinses. Other taste-testing me- 

 thodologies have also been tested, and the 

 latter yield inconsistencies in the data which 

 did not occur with the modified Harris-Kalmus 

 procedure. 



Ninety-four monozygotic twins have thus far 

 manifested 1 00 percent concordance for the 'sensi- 

 tive taster' vs. 'insensitive ("non"-)taster' dichot- 

 omy. These data contrast significantly with the 

 low concordance observed in same-sex di- 

 zygotic twins. Furthermore, using a series of 

 fourteen dilutions, all the above monozygotic 

 twin pairs manifested taste threshold concord- 

 ance within a single serial dilution. One ex- 

 ceptional and discordant pair includes one twin 

 on hormone therapy, who is an insensitive 

 ("non"-)taster while her co-twin is a 'taster.' 

 Two other variables which evidently affect taste 

 threshold for PROP are aspirin medication, and 

 coincidence within the first three days of men- 

 struation. Threshold discordance coinciding 

 with either of the above variables disappeared 

 in each case upon controlled retest. 



292 



