Knight — 72 — Dictionary 



Heterozygote, Complex. — A heterozygote whose gametes 

 have numerous differences which segregate as a unit (Rennee; 

 Darlington). 



Heterozygotes, Proportion of. — In a population mating at 

 random, the proportion of individuals heterozygous for any 

 particular gene can be found from the equation p- :2pq :q- 

 where p- and q- are the proportions of the two homozygous 

 classes respectively, 2pq represents the proportion of hetero- 

 zygotes, and p + q =^ 1. 



Heterozygous. — Derived from the union of gametes of dis- 

 similar genetic constitution. 



Heterozygous Sex. — That sex in which the sex chromosomes 

 are dissimilar or in which the sex chromosome has no homo- 

 logue. Gametes produced by the heterozygous sex are of two 

 kinds with regard to their properties of sex determination. 

 See Y-chromosomes and \V -chromosomes. 



Hexad. — Unequal bivalent (not trivalent) formed by pairing 

 of one chromosome with its homologue which has fused with 

 a third non-homologous chromosome, in a fusion heterozygote 

 (McCluxg ; Darlington ) . 



Hexaploid. — Having six haploid sets of chromosomes in the 

 somatic cells. 



Hexoestrol. — This synthetic oestrogen is more active than 

 either oestrone or stilboestrol. See under Oestrogens. 



Hexuronic Acid. — Ascorbic Acid, vitamin C, CgHgOg, a 

 water-soluble anti-scorbutic vitamin. 



Hinny. — The offspring of a stallion and a she-ass. 



Histogenesis. — The formation or differentiation of spe- 

 cialised tissues. 



Hofacker & Sadler Law. — The theorv' that sex determination 

 is affected by the relative ages of the male and female parents. 

 An older male parent was supposed to give a predisposition 

 to male offspring and a male parent younger than the female 

 was thought to produce a higher proportion of females in the 

 offspring. 



Holandric. — Of a character : passing direct from male to male 

 through the Y-chromosome. 



Hologametes. — Gametes which are of similar size to typical 

 cells of the species, and which are not formed by meiosis. 



Hologamy. — Having gametes which are not formed by meiosis 

 and which resemble the ordinary somatic cells of the or- 

 ganism; the fusion of such gametes. 



Hologenic. — Of a sex -linked character : passing direct from 

 female to female. 



