The levels of ABO plasma agglutinins were studied in 47 MZ and 30 same-sex DZ pairs of twins having the same blood group. The degree of genetic determination of this characteristic, as ascertained by the comparison of average titers and titration scores, does not seem to be high; despite the fact that the correlation coefficients were always lower among DZ, the F ratio was significant in relation to the anti-B of A persons only. The presence of these antibodies was also investigated in the saliva of 30 MZ and 26 DZ pairs. Since about the same degree of discordance was observed among these two types of twins, the role of inheritance in the variability of this trait must be low.

Fifty MZ and 51 same-sex DZ twins were studied for ABH salivary secretions and the amount of these substances measured in those with the same A1A2BO blood groups. Using the classical, manual inhibition test we verified: (a) Levels for the H antigen in A2 and B persons similar to, but in O and A1 lower than those obtained in other places; (b) Low averages for the A and B substances; (c) Mean intrapair differences for A and H, which were the double in DZ as in MZ twins, the estimated degree of genetic determination being 0.86 and 0.69 respectively; in both cases the F-ratio was significant at the 0.01 level; (d) If one discrepant family is disregarded the correlation coefficient between O parents and DZ children for the H antigen (0.48) is of the order of magnitude expected under a simple additive model of polygenic inheritance.

Tests were also made using a fully automated method. The intraclass correlation coefficients thus obtained in MZ and DZ were similar to those reached using the data obtained with the classical technique. The degree of concordance arrived at by the two methods was only fair, but this may have been due to extraneous factors related to the way the samples were handled.

On the basis of the parameters of gene stability suggested by Gedda-Brenci's model on the Ergon/Chronon System, a mathematical and a stochastic model of gene decay are worked out.

The present paper reviews the research lines which have been explored to evaluate to what extent genetic factors are intervening on the mechanism of resistance and susceptibility to leprosy.

It presents a critical discussion of the investigations on the familial association of leprosy, familial association of leprosy types, intrafamilial contagion of leprosy, concordance of leprosy in twinpairs, racial differences on leprosy prevalence and lepromatous rate, pedigree studies, association of leprosy to genetic markers, Australia antigen, and dermatoglyphic patterns. Space was also allotted to review family and twin-pair studies on the Mitsuda reaction, as well as to the investigation on the in vitro behaviour of blood macrophages against killed M. leprae.

Some areas in which further research on leprosy and genetics may be considered as prioritary are outlined with some detail.

Primidone and its metabolites Phenobarbital and Phenylethylmalondiamide were tested in cultures of human lymphocytes on possible effects of inducing chromosome aberrations. The substances examined ranged from concentrations lower than the therapeutic serum level to 10-75 times this value, which differed with the various substances. Phenylethylmalondiamide shows, besides an increase of spiralization defects at higher concentrations, which was typical for all three substances, no reaction on the chromosome structure.

By using the Friedman-test a statistically significant difference (P < 5%) could be found between the average aberration rates of the controls and the cultures which had been treated with Primidone and Phenobarbital. The test according to Wilcoxon and Wilcox shows that there is a statistically significant (P < 5%) difference between the aberration rates of controls and the respectively treated cultures. The higher values for percentage of aberrant mitoses are caused by the increase of gaps and breaks. There was, however, no proof for a linear dependence of the percentage of aberrant mitoses on the increasing concentrations of the substances. The number of tetraploid mitoses, endoreduplications and hyperploid cells was within the normal range.

Since in these investigations the number of chromosome exchanges was not increased, it can certainly be said that Primidone and Phenobarbital are not highly mutagenic substances.

The models of gene decay, previously worked out on the basis of Gedda-Brenci's Ergon/Chronon System, now undergo an analytic simulation, in order to verify how the mathematical model fits the stochastic one.

The acridine orange staining of metaphases previously treated with hot salt solutions, exhibits a differential banding pattern of the chromosomes. According to the physicochemical interpretation of the stained structures, the green and red fluorescent segments of the chromosomes should be considered as constituted respectively by double-stranded DNA and single-stranded DNA. The banding pattern is relatively consistent in different metaphases, although some occasional variations of the bands may be referred to the interference of chromosomal acid proteins. In general, the sequence of the bands is compatible with the picture of the reverse banding.

The results are presented of a method of generalized distances calculated by a noncentral χ2 test and applied to compare 63 twin pairs and 196 sib pairs. The advantage of this method in biometrical analysis lies in the fact that several measurements can be utilised simultaneously. Besides, it takes into account the distance of each relative to the centre of the population and also has the advantage of permitting the comparison of distances between pairs of relatives whatever their age or sex.

Generalized distances were calculated for four measurements of the head, five of the body and eleven of the face. For all three sets of measurements the influence of genetical factors was demonstrated. The body seems less influenced by environmental factors and more conditioned by genetic ones.

Comprehension of etiologic factors in cancer requires precise recording of tumor histology, genealogy, medical history, and potential environmental carcinogens. With this approach and in a prospective and retrospective survey, two cancer-prone and two cancer-resistant families are described. Genetic factors, in cancer predisposition and in cancer resistance are hypothesized.

The population of Andhra Pradesh has been considered ideal for the study of inbreeding effects in view of its high incidence of consanguinity. Information for the present investigation was obtained from 1,091 consecutive hospital single births to study the genetic load in the newborn in terms of mortality and malformation as a consequence of inbreeding. The nature of consanguinity was examined and the frequency of uncle-niece marriages was found to be lower than in other parts of Andhra Pradesh. The mortality load in the newborn was found to be two lethal equivalents per individual, while the malformation load at birth was half the mortality load.

Since the MNS blood group system does not exhaust the total degrees of freedom under the Wright's equilibrium law, it was felt that the peculiar problems facing the detection of F (the fixation coefficient of Wright's model) from ABO blood group data may not be totally relevant to the MNS system. To verify this, a short discussion on the detection of F from MNS blood group data is given here.

A chromosomal study has been carried out on 11 patients with otosclerosis. All caryotypes were invariably normal. Those group-D chromosomal anomalies of structure and number reported in the literature could therefore not be confirmed.

Two remarks on Rao's Two-Gene Hypothesis for the inheritance of hypertrichosis of ear rims are offered here. First remark provides justification for the particular location of NH- and H-loci on the sex chromosomes in man. A single-case longitudinal study is also reported, which gives rise to the possibility of testing the two-gene hypothesis on family data.

A scoring method for the diagnosis of Turner's syndrome (T.S.), based on five dermatoglyphic and four skeletal characteristics, showing significant frequency variations between patients and normal females, is presented. The dermatoglyphic characteristics include: total finger ridge count, ab ridge count, maximal atd angle, T line terminating in the second interdigital interval, and presence of hypothenar patterns. The skeletal characteristics include: carpal sign, metacarpal sign, phalangeal sign, and abnormally shaped distal phalanges. Arbitrary score numbers have been assigned to each characteristic, depending on the magnitude of the difference between patients and controls; the partial scores were added up to form the final T.S. score. The diagnostic value of T.S. score has been proved, since it is well separating the patients from normal females. The probability that an individual with a given T.S. score has the Turner's syndrome has been estimated.

Taste blindness for PTC has been studied in (a) 416 leprosy patients and 424 healthy subjects, and (b) 261 filarial patients and 136 normal individuals of both sexes. A significant difference was found between leprosy patients and the healthy control group in the proportion of nontasters (χ2 = 4.096, for 1 DF, P〈0.05). No significant difference could be observed between the filariasis and the control group (χ2 = 0.605, for 1 DF, P〉0.30).

A genetic study has been carried out on tongue pigmentation in man, based on 10 pedigrees and 39 Indian populations. It is concluded in favour of a genetic basis of the trait, which would be inherited as an autosomal recessive.

Two pairs of sisters are reported who showed clinical, morphologic, and hormone abnormalities, such as to be classified in the picture of the so-called Stein-Leventhal syndrome.

These cases, as other few similar observations, may suggest the possibility that, at least in some instances, the Stein-Leventhal syndrome can be governed by factors of a genetic order.

After a short review of the literature on this subject, it is pointed out that enough evidence supports the existence of predisposing genetic factors to the manifestation of the syndrome, although a true heredity of the disease cannot at the moment be entirely supported. Also some fraternal cases could find an explanation in lesional actions repeated during subsequent pregnancies.