FOUNDATIONS FOR SEX 



59 



nondisjunction at the second meiotic divi- 

 sion. 



If the hypothesis of crossing over is ac- 

 cepted, the color-blind locus separates freely 

 from its kinetochore and would suggest that 

 the position of the locus is at some distance 

 from the kinetochore of the X chromosome. 



A disturbed balance between the X and 

 the Y chromosomes alters the sexual type. 

 A single Y chromosome, contributing fac- 

 tors important to male development, is able 

 to alter the effects of two sets of female 

 influencing X chromosomes. Yet two Y 

 chromosomes in a complex of XXYY plus 

 44 autosomes seem to have little or no more 

 influence than one Y (Muldal and Ockey, 

 1960). The locations of the sex-influencing 

 genes in man are thus more like those of the 

 plant Melandrium than of Drosophila in 

 which the male-determining factors occur 

 in the autosomes. The relative potencies of 

 the male sex factors compared with those of 

 the female, however, are much less than 

 those in Melandrium. 



6. Turner Syndrome 



Turner's syndrome or ovarian agenesis 

 further substantiates the female influence 

 of the X chromosomes. The cases occur as 

 the developmental expression of accidents in 

 the meiotic or mitotic divisions of the chro- 

 mosomes. These accidents lead to adults 

 unbalanced for the female tendencies of the 

 X chromosome. The gonads consist of con- 

 nective tissue. The rest of the reproductive 

 tract is female. Growth stimuli of puberty 

 are lacking, resulting in greatly reduced fe- 

 male secondary sexual development. Pa- 

 tients are noticeably short and may be ab- 

 normal in bone growth. In its more extreme 

 form, designated as Turner's syndrome, the 

 individuals may show skin folds over the 

 neck, congenital heart disease, and subnor- 

 mal intellect, as well as other metabolic 

 conditions. Earlier work (Barr, 1959; Ford, 

 Jones, Polani, de Almeida and Briggs, 

 1959) shows that 80 per cent of the nu- 

 clear chromatin patterns are of the male 

 type. Evidence from families having both 

 this condition and color blindness suggested 

 that at least some of the Turner cases would 

 be found to have 45 chromosomes, the sex 

 chromosome being a lone X (Polani, Lessof 

 and Bishop, 1956). Work of Ford, Jones, 



Polani, de Almeida and Briggs, (1959) 

 has confirmed this hypothesis and added the 

 fact that some of these individuals are also 

 mosaics of cells having 45 and 46 chromo- 

 somes. The 45 chromosome cells had but one 

 X, whereas the 46 had two X's. This finding 

 may explain the female-chromatin cell type 

 observed in about 20 per cent of the cases 

 having the Turner syndrome. Such mosaics 

 of different chromosome cell types could 

 also be significant in reducing the severity 

 of the Turner syndrome and in increasing 

 the range of symptoms which characterize 

 this chromosome-caused disease as con- 

 trasted with those characterizing Turner's 

 disease. Further cases observed in other 

 investigations, Fraccaro, Kaijser and Lind- 

 sten (1959), Tjio, Puck and Robinson 

 (1959), Harnden, and Jacobs and Stewart 

 cited by Ford (1960) have all shown 45 

 chromosome cells and a single X chromo- 

 some. As with the XXX plus 44 autosome 

 super females, the Turner type, X plus 44 

 autosomes, also shows a rather wide range 

 in development from sterility with extensive 

 detrimental secondary effects to nearly nor- 

 mal in all respects. Bahner, Schwarz, Harn- 

 den, Jacobs, Hienz and Walter (1960) re- 

 port a case which gave birth to a normal 

 boy. Other cases have been described (Hof- 

 fenberg, Jackson and jVIuller, 1957; Stewart, 

 19601 in which menstruation was estab- 

 lished over a period of years. The XO type 

 in man and Melandrium is morphologically 

 female. In Drosophila on the other hand, 

 the XO type is phenotypically nearly a 

 perfect male. It is further to be noted that 

 the X chromosome of Drosophila appears to 

 have a less pronounced female bias than 

 that of man when balanced against its as- 

 sociated autosomes, inasmuch as the XO + 

 2A type in Drosophila is male as contrasted 

 with the XO + 2A type in man which is 

 female. At the same time it seems that the 

 autosomes in the human may be influential 

 in that the female gonadal development is 

 suppressed instead of going to completion 

 as it does in the XX type. 



7. Hermaphrodites 



Hermaphroditic phenotypes in man, to 

 the number of at least 74 (Overzier, 1955), 

 have been observed and recorded since 

 1900. Types with a urogenital sinus pre- 



