Section 15 — Human Genetics 



to use blood-groups and haptoglobines. The 

 blood-groups and haptoglobines were deter- 

 mined in 200 twin-pairs. All of 56 monozygotic 

 twins were concordant, while only three of 81 

 twins with the same sex were concordant. 



somatic cells preserved by freezing. An increase in 

 abnormalities of progeny has not accompanied 

 the use of frozen-stored bovine and human sper- 

 matozoa. The current view is that there is no 

 such genetic damage. 



1. Fertil. & Steril 14, 49-64, 1963. 



15.9. Disparity of Colour Vision in Uniovular Twins. 



J. Zanen and A. Meunier (Brussels, Belgium). 



The authors relate two cases of uniovular 

 twins. The colour vision normal for one of them, 

 is wrong for the other and belongs respectively 

 to protanopia or deuteranomaly group. 



They add a third case where the twins are both 

 deuteranomalous, but the disparity was so slight 

 that it was not significaat. 



15.10. Banks for Frozen-Stored Human Spermato- 

 zoa. J. K. Sherman (Little Rock, U.S.A.). 



Feasible applications of frozen-stored human 

 spermatozoa include: clinical treatment of in- 

 fertility with donor or husband's semen, main- 

 tenance of husband's fertility in absence of 

 testes, in old age and in death; ready availabi- 

 lity of spermatozoa bearing desired genetic 

 characteristics for unusual blood types, etc; 

 protection from radiation induced genetic alter- 

 ations on earth and in space; and eugenically 

 directed population control and selection. 

 Successful banking of human spermatozoa pre- 

 served by freezing is dependent upon several 

 considerations. In addition to simplicity and 

 efficiency, methods employed must favor mini- 

 mal loss of spermatozoal motility, retention of 

 fertilizing capacity, and absence of genetic 

 alteration. Superiority of the author's combined 

 freezing and storage method using liquid ni- 

 trogen-vapor( 1 ) is shown in comparison with 

 earlier dry-ice method. After an average freeze- 

 thaw survival of 70 per cent, no further motility 

 loss occurred during storage at — 196°C for three 

 years, the longest period observed, while 10-20 

 per cent was lost at — 75°C. Retention of fertiliz- 

 ing capacity of human spermatozoa preserved 

 by nitrogen-vapor method is reported. Possibility 

 of freeze-thaw induced genetic damage is re- 

 cognized. Integrity of normal and malignant 

 cells for research is maintained in frozen-storage 

 and frozen bovine semen is used routinely to 

 breed millions of dairy cattle. No alteration in 

 chromosomal structure or reflected cellular 

 function has been reported with mammalian 



15.11. Selection Relaxation in Man. R. H. Post 

 (Ann Arbor, U.S.A.). 



The relaxation of selection pressures against 

 deleterious traits resulting from cultural growth 

 can be demonstrated by the markedly higher 

 frequencies of red and green "colorblindness" 

 among populations in Europe and the Far East, 

 contrasted with the lower frequencies prevalent 

 among populations living in hunting habitats, 

 such as Australian aborigines, Eskimos and 

 certain American Indians. Frequencies are 

 approximately four times higher in the former 

 populations than the latter, i.e. some 6 and 1.5 

 per cent, respectively, for the mutant alleles at 

 the deuteron locus, and some 2 and 0.5 per 

 cent respectively, at the protan locus. 



The demonstration depends upon certain 

 assumptions which appear reasonable, although 

 they are not yet proven. Evidence is presented 

 for the selective disadvantage of "colorblindness" 

 in hunting habitats and its relative unimportance 

 in most walks of life among non-hunters. 



The two loci are quite closely linked on the 

 X-chromosome. Diagnosis is fairly facile and 

 reliable at early ages, environmental effects and 

 age changes are negligible, and published data 

 are sufficient to permit comparisons among 

 populations which vary in habitat or cultural 

 history. 



Rough estimates of mutation rates can be 

 made by dividing the difference in gene frequen- 

 cies between hunters and non-hunters by the 

 number of generations which have elapsed since 

 the ancestors of the latter relinquished their 

 hunting habitats, under the assumption that 

 relaxation has been complete since that time. 



Analysis of the frequencies of "colorblindness" 

 among geographic areas within several countries 

 together with their cultural histories gives 

 further support to the relaxation hypothesis, 

 viz. Britain and France, Japan and China. 



Population differences in vision acuity and 

 hearing acuity offer less satisfactory opportuni- 

 ties for demonstrating selection relaxation. 

 Frequency data for several different populations 

 are presented, with discussion. 



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