Section 15 — Human Generics 



Cytologic studies of peripheral blood from 

 affected as well as normal members were per- 

 formed. A defect involving an extra chromosome 

 was found to be present. 



15.26. Deviations from the Mendelian Laws in 

 Human Families. The Action of Natural Selec- 

 tion on Blood Groups in Twins. L. E. Nijen- 



huis (Amsterdam, the Netherlands). 



Previous population studies gave evidence for 

 strong action of natural selection on blood 

 groups, which varies more together with the 

 genome composition than with environmental 

 factors! 1 ). The explanation could be that cer- 

 tain genomes provide more viability than others. 

 Other indications for this phenomenon might be 

 found in family studies, and especially in twin 

 studies, because the less viable partner may be 

 superseded by the other. Dizygotic twin partners 

 are more often double concordant of discordant 

 for factors belonging to two different blood 

 group systems than would be expected. 



As to the MN and Rh groups an excess of 

 10 per cent double discordance and concordance 

 is observed for the single gametes transferred by 

 the parents, independent of the way of combina- 

 tion, i.e. MN and Rh alleles from the same parent 

 or not. This gives rise to the conclusion that 

 selection takes place after fertilization. If in the 

 parents combination heterozygosis exists for 

 both systems, the excess is 22 per cent. This is 

 only 12 per cent if both parents are homozygous 

 for MN or Rh, which indicates that the selection 

 is exercised on genes linked with the blood group 

 loci. Excess of double discordance and con- 

 cordance can also be observed, though in a 

 lower degree, in non-twin family studies. 



1. Nijenhuis, 2nd Intern. Conf. Hum. Genet., 

 Rome, 1961. 



15.27. Genetics and Linkage Relations of the Lp 

 Serum Type System. Jan Mohr and Kare 

 Berg (Oslo, Norway). 



The discovery of a serum type system con- 

 cerning human ^-lipoproteins is reported. 



From a material of Norwegian unrelated 

 individuals and families a hypothesis of deter- 

 mination by a gene pair Lp a and Lp a is proposed, 

 the estimates of gene frequencies in the Nor- 

 wegian population being about 0.19 and 0.81 

 respectively. 



Linkage relations with other marker systems 

 are considered. 



15.28. Linkage Studies in Families with Pathological 

 Dominant Traits. Walter Scholz (Munster, 

 Germany). 



Linkage studies in man are made more pro- 

 mising by the availability of an increasing num- 

 ber of well-suited and well-defined marker genes, 

 especially in serology. Families showing regular 

 dominance of pathological traits are best suited 

 for such investigations. The following antisera 

 have been used in the present investigation, 

 anti-A, -B, -AB, -Ai, -A 2 , -M, -N, -S, -s, -P, -D, 

 -C, -O, -c, -E, -e, -K, -k, -Fy a , and Jk b .— 

 Haptoglobin types and gamma globulin groups 

 Gm(a) and Gm(x) were used as additional mar- 

 kers. Linkage data were received for families 

 with dominant characters as hereditary mul- 

 tiples exostoses, telangiectasia hereditaria (mor- 

 bus Osier), Polydactyly, syndactyly, ectrodactyly 

 and others. The results of these investigations 

 will be given in particulars and discussed. 



Details will be published in the Z. /. menschl. 

 Vererb.-u. Konst.-Lehre, 1963. 



15.29. Scoring for Linkage Between Several Loci. 

 Cedric A. B. Smith (London, Great Britain). 



The detection and estimation of linkage be- 

 tween two loci is most simply done by using 

 Morton's z scores. However, when tests are 

 made on three or more loci on the same chro- 

 mosome, as already happens on the X chro- 

 mosome, new problems arise. Families may be 

 investigated because of the presence of one 

 sex-linked character, and then used to deter- 

 mine the strength of linkage between two 

 others. This will require the use of new types of 

 score correction. 



15.30. Male and Female Recombination Fractions 

 in Man. J. H. Renwick (Glasgow, Great 

 Britain). 



The linkage data from 27 pedigrees of the 

 nail-patella syndrome have been analysed by 

 the computer programme of Renwick and Schul- 

 ze (1961). A search has been made for incon- 

 sistencies in the nail-patella: ABO linkage of the 



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