In his recent book Dr. Roy J. Schepherd states that:“Further information of genetic effects is likely to be derived from comparisons of identical (monozygotic) and fraternal (dizygotic) twins. Gedda (1961) has already shown that identical twins are more likely to have a similar interest in sports than are fraternal twins. It would be interesting to carry out comparisons of maximum oxygen intake and other objective measurements of endurance fitness on the two classes of twins, but this crucial experiment has yet to be completed”.We are very glad to be able to announce here that Dr. Schepherd's wish is being fulfilled within the scope of a wider research project undertaken jointly by the Gregor Mendel Institute for Medical Genetics and Twin Research and the Italian Olympic Committee's Institute of Sports Medicine under the auspices of the Italian Sports Medicine Federation.The studies we have undertaken aim to assess the respective roles of genetic and environmental factors as related to selection and training in sports and physical education.The twin method affords, through a comparison of MZ and DZ within-pair concordances, an assessment of the degree of genetic conditioning in any individual trait.It is quite obvious that the possible influence of training on any given trait is inversely proportional to the degree of genetic conditioning of the same trait.If a given trait, required for a certain type of activity, is completely or almost completely conditioned by the genotype, we should seek those who have inherited it from their parents without wasting time and effort in useless training sessions.As we can see, the scientific information we are seeking has great practical importance in the selection and training of athletes in every single field of sports and physical education.

SUMMARYThe Authors have analyzed the data concerning length of gestation and neonatal weigth and length measurements in 2,440 living twin pairs (from the files of the Mendel Institute), in order to verify the frequent assumption that all twins should be considered as prematures and, as such, affected by congenital debility.Comparing their findings with the standard values for prematures, they reach the conclusion that the majority of twins who have survived the perinatal period were not prematures. Furthermore, the less developed among such twins differ from single-born prematures by reason of their subsequent normal auxologic development, whereby the Authors propose that they should rather be considered as “premature-like”.

SummaryThe Authors report on the steps involved in the computerization (coding of data, card punching and tape recording) of a Twin Register initiated in 1942 and currently approaching 11,000 cases of multiple births.The Register is permanent in that it involves continued updating of information and addition of new cases. It includes twins of any age, sex, zygosity and health condition.The experience gained in the reported project can be usefully shared in wiew of international cooperation and standardization.

Zygosity determination is generally carried out by different methods in small or large twin samples. The probability method based on sex and genetic markers is limited to relatively small samples, as a consequence of its cost. The empirical questionnaire method is applied in several large twin registers. Its margin of error is low enough for population studies, its cost is negligible, but its accuracy is insufficient when zygosity of twin pairs included in definite samples must be individually assessed. Efforts to bridge the distance between the two methods should be made, and they may take either direction: (1) find new, inexpensive genetic markers, or (2) increase the number and accuracy of empirical methods. The accuracy of a number of empirical methods applied to a twin sample of established zygosity has been compared. One modification of the “two peas in a pod” method, originally called “equivocalness method”, appears to warrant inclusion in questionnaire methodology. Also, compound probability as expressed by several empirical methods may reach an acceptable level of accuracy in zygosity assessment.

Several studies have appeared in the literature to support the hypothesis of a differential incidence of twin births according to the antigenic structure of maternal erythrocytes (Gedda, 1961).Osborne and DeGeorge (1957) wrote that twin births exhibit a higher incidence when mothers belong to group O, as compared to other groups within the ABO system; a similarly increased incidence of twin births was indicated for rh-negative mothers within the Rh-Hr system.The availability of a large number of immunohematological data concerning twin pairs and nontwin individuals examined in our Institute have encouraged us to verify whether this material could reveal some a posteriori effect of the selective tendencies that have been related to the parental level.Limiting our study in this phase to the ABO system, we have collected data on 1190 twin individuals and 1454 nontwin individuals, for all of whom the ABO blood group had been recorded.The first step in our analysis was the perequation of the nontwin distribution to the twin distribution, obtaining the figures reported in the column “controls” in Tab. I.