Y chromosome analysis reveals a sharp genetic boundary in the Carpathian region.

Nine single nucleotide (SNP) or indel binary polymorphisms were used to determine the frequencies and phylogenetic relationships of 12 Y chromosomal haplogroups in 289 males from Romania and the Republic of Moldova. Our data indicated a low but not null rate of the homoplasic appearance of the DYZ3 (-) allelic state. All other markers confirmed the previously proposed phylogeny. Based on the affinities between populations in terms of haplogroup frequencies, this work identified the geographical region of the Carpathians as a break point in the gene geography of Eastern Central Europe, providing a finer definition of one of the possible sharp genetic changes between Western and Eastern Europe.

Population structure in the Mediterranean basin: a Y chromosome perspective.

The Mediterranean region has been characterised by a number of pre-historical and historical demographic events whose legacy on the current genetic landscape is still a matter of debate. In order to investigate the degree of population structure across the Mediterranean, we have investigated Y chromosome variation in a large dataset of Mediterranean populations, 11 of which are first described here. Our analyses identify four main clusters in the Mediterranean that can be labelled as North Africa, Arab, Central-East and West Mediterranean. In particular, Near Eastern samples tend to separate according to the presence of Arab Y chromosome lineages, suggesting that the Arab expansion played a major role in shaping the current genetic structuring within the Fertile Crescent.

Natural selection associated with birth weight. V. The secular relaxation of the stabilizing component.

The secular trend of stabilizing selection on birth weight has been studied during the last decades in 17 countries, representative of America, Asia and Europe. A relaxation of the intensity of selection is regularly observed, which can probably be attributed to a progressive reduction of the environmental component of birth weight variance.

Stabilizing selection in man: the effect of mother's age on birthweight variance.

In order to study the effect of mother's age on birthweight variance, data were collected from Official Vital Statistics of the USA, Japan and Italy. Birthweight means and variances were calculated for all single births and for live births only. The results demonstrated that birthweight variance regularly increases in babies born to mothers of increasingly older age (with the exception of the youngest mothers). Moreover, the higher the variance in all births, the more the variance diminishes after late fetal selection. Therefore, a feedback phenomenon takes place in the stabilizing component of selection, i.e. the difference between the variance of all births and that of live births. As a consequence, at least part of the higher number of fetal losses experienced by older mothers can be attributed to the increased birthweight variance of their children.

Secular trend of twin concordance in late fetal death.

In the present paper the secular trend of twin concordance for late fetal death rate has been analysed. The results show that, while the correlation remains unchanged in MZ twins, it is greatly reduced in DZ twins. This renders untenable the assumption of comparable secular trends in the intrauterine environment of the two types of twins. An appropriate model is given for the estimation of the environmental (intrauterine) factors in late fetal concordance, under the assumption of a wide range of frequencies for unconditional lethals.

Natural selection associated with birth weight. VI. Towards the end of the stabilizing component.

The secular trend for stabilizing selection on birth weight has been analysed in Italy from 1954 to 1985 in order to study changes in the forces of natural selection which have occurred as a consequence of progress in health care. In previous papers we demonstrated a very rapid relaxation of stabilizing selection on birth weight. In this paper we show that in the last few years this kind of selection has been coming to an end for the vast majority of Italian newborns.

Genotype-environment relationships: an analysis of stature distribution curves during the last century in Italy.

The secular trend of stature in Italy from 1874 to 1960 has been examined using military records concerning nearly complete samples of males born in Italy in given years. The national mean value increased by nine cm (about one cm/decade) and the averages of the different Italian regions tend progressively to aggregate towards higher values (the north) and lower ones (the south). The rate of increase of stature was more or less constant up to subjects born in 1945, but in the period 1945-55 a very steep increase was observed. In more recent times, a clear slowing down has taken place both at national and regional level. The following moments around the mean were investigated: (1) variance--the national value has remained more or less constant and regional values pass from very diverse figures to very similar ones; (2) skewness--the initially negative national value has become slightly positive; in the regions, from very diverse negative values a close aggregation around zero is recently attained; (3) kurtosis--initial national hyperkurtosis has reduced to values typical of the Normal distribution; the same is true for regional figures which, moreover, have become closely aggregated. The increasing fit of stature distribution to the Normal distribution agrees with the hypothesis of an increasing expression of the genetic endowment in consequence of a progressive improvement in living conditions.

Effects of environmental changes on the phenotypic expression of human polygenic traits.

The very large increase in adult stature during the last century is well documented for many countries and this phenomenon has been associated with the rapid improvement of environmental conditions. In the case of Italy, data relative to its regions and drawn from the military records of the last century showed a rapid normalization (i.e. elimination of both negative skewness and hyperkurtosis) of the distribution (1874-1938), followed by acceleration of the average increase (1938-57), which is now approaching a plateau (1957-64). Two different interactions between genotype and environment are hypothesized: the curve normalization is interpreted as being due to the elimination of extremely unfavourable conditions which inhibit growth, while the rapid stature increase is possibly due to the achievement of an environmental threshold, such as to permit a complete expression of the genetic potential. In fact, under the multifactorial model, a perfectly normal distribution is expected, unless there is differential selection before age 18.

Breakpoint distribution in constitutional chromosome rearrangements with respect to fragile sites.

In an attempt to investigate possible relationships between fragile site bands and chromosome abnormalities, we have analysed the distribution of 6391 breakpoints found in constitutional rearrangements. Were relative band lengths to be ignored, a general trend for breaks to be located in fragile site bands would be confirmed. On the other hand, no difference was detected between bands with or without fragile sites if the probability of breakage for each single band is assumed to be proportional to its length. Nevertheless, a number of bands with a great excess of breakage events were identified.

The effects of demographic transition on the opportunity for selection: changes during the last century in Italy.

The index of opportunity for selection proposed by Crow has been calculated for the Italian population during the last century. The evolution of its two components, the pre-reproductive mortality and the variance in fertility, has been also analysed and compared with similar data for the United States. The results clearly show the relevance of socio-economic changes to the evolution of selective patterns in our species; in particular the relative incidence of mortality and fertility to selection intensity: the total index has in fact been reduced by 75% during the last century, the relative amount due to fertility increasing from 57 to 89%. The probable different relevance of genetic factors in the two components has also been discussed.

Individual variability in the translational regulation of ribosomal protein synthesis in Xenopus laevis.

Ribosomal protein synthesis is regulated by controlling the fraction of mRNA associated with polysomes. It is known that this value changes in different developmental stages during Xenopus embryogenesis or, more generally, with changing cell growth conditions. We present here an analysis of the proportion of mRNA loaded on polysomes, carried out with probes for five different ribosomal proteins on several batches of Xenopus embryos obtained from different individuals. The results obtained indicate the existence of probe-dependent and individual differences, which reflect genetic variations in the cis- and trans-acting regulatory elements responsible for translational regulation. The fraction of ribosomal protein mRNA loaded onto polysomes can be used as an index of an individual's capacity for ribosome production.

A demographic investigation of the four Albanian communities living in Molise, Italy.

In a study of the four Albanian villages of Molise, Italy (Campomarino, Montecilfone, Portocannone and Ururi), demographic data have been obtained through national censuses and direct interviews of 382 subjects. The data demonstrate an increase of the population from 1700 to the middle of the twentieth century. From that time the population decreases in three villages, which now present a considerable degree of ageing. On the contrary, in the fourth village (Campomarino) the population continues to increase during the second half of the twentieth century, and now appears as a relatively young population. Immigration has proved to be somewhat elevated and shows a diminishing trend from the great-grandparents to the propositi. The endogamy decreases passing from the generation of the great-grandparents to that of the parents, and is higher along the paternal ascendence than along the maternal one. The exogamy, on the contrary, increases passing from the generation of the greatgrandparents to that of the parents, demonstrating a rather considerable mixture with the surrounding population. The percentage of Albanian surnames, or those of probable Albanian origin, has also been estimated in the parents of the propositi, and resulted to be higher in Montecilfone and Ururi, in comparison with Campomarino and Portocannone.

Natural selection associated with birth weight. I. Selection intensity and selective deaths from birth to one month of life.

Differential mortality as a function of birth weight was studied up to the 4th week of life in all single births in Italy in 1974. It was found that: (i) Both selection intensity and selective mortality are much higher with increasing immaturity. (ii) For babies born at term or after 8 months of pregnancy selection intensity tends to relax as early as one week after birth, while for those born after 7 months selection is at work for a longer period. (iii) Selective mortality, on the other hand, keeps increasing after birth but its relevance is relatively decreasing since average mortality after birth continues to decrease.

Natural selection associated with birth weight. II. Stabilizing and directional components.

The differences of birth-weight distributions before and after selection by the different components of perinatal mortality were studied for all single babies born in Italy in 1974. It was found that: (i) In mature babies the selection is mainly stabilizing while the directional type is almost negligible. (ii) In immature babies both stabilizing and directional selection are at work, greatly modifying the birth weight distributions.

The switch from haemoglobin F to A: the time course of qualitative and quantitative variations of haemoglobins after birth.

The time course of the transition from HbF to HbA production in the postnatal period has been studied. The description is based on the time-dependent pattern of total haemoglobin and of HbF observed in an 8 months follow-up of 25 premature newborns. The absolute amount of HbF decreases exponentially from birth to approximately 25 weeks (from 15.56 +/- 0.48 g/dl to 0.66 +/- 0.08 g/dl), at a weekly rate of approximately 16%. On the other hand, HbA shows a biphasic pattern: first it decreases slightly from birth to 6 weeks (from 4.09 +/- 0.32 g/dl to 2. 63 +/- 0.33 g/dl); afterwards it increases exponentially at a weekly rate of 5% up to a plateau value, until HbF is almost completely replaced by HbA. Therefore the total haemoglobin decreases exponentially from birth to approximately constant for the next 6 weeks, and thereafter it increases very slowly. From these data, two distinct phases of postnatal erythropoiesis can be identified: the first (from birth to 6 weeks) is characterized by a decrease in the total amount of haemoglobin produced whereas in the second there is an alteration in the relative proportions of HbF and HbA being synthesized.

Changes of selection opportunities with a changing environment: regional heterogeneity in Italy.

The mortailty and fertility components of the index of opportunity for selection (the Crow index) have been studied in the various Italian regions during the last century. To estimate the relevance of environmental factors on both components, their trends and those of their interregional variances have been compared with illiteracy. The results show that the selection opportunities due to mortality have decreased in a smiliar way in all the regions with a trend parallel to that of the national percentage of illiteracy, suggesting that this component is directly affected by the general socio-cultural level. As to the component due to fertility differentials, the regions, though scattered in the time scale, show a characteristic cycle of rise and fall. Moreover, the interregional variances of this component and of illiteracy are quite parallel, thus supporting the hypothesis that the reproductive pattern is strongly influenced by the individual cultural level.