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.

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.

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.

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.

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.

A case is described of pseudo-pseudo-hypoparathyroidism, with the following symptoms: round face, large forehead, relative backwardness, short stature, relative obesity, congenital muscular torticollis, cervical fused vertebrae, spina bifida occulta cervicalis, bifid rib, bilateral brachymetacarpy IV. Some of these also occur in the basal-cell nevus syndrome. The patient does not however show a basal-cell carcinoma, nor mandibula cysts.

A pair of MZ twins with diagnoses of chronic simple schizophrenia has been studied from the genetic, social, medical, and psychiatric standpoint by members of the several professions. Clinical psychologists studied the patients independently and on the basis of psychometric and projective tests found a remarkable similarity in personality profiles. An in-depth family study failed to reveal any evidence of psychiatric disease in other relatives. Consanguinity was absent. The family unit is typical of that described frequently for a schizophrenogenic household, i.e., dominant mother, passive father. Genetic etiologies are discussed in context with occurrence of schizophrenia in MZ twins in this particular family setting.

A twin pair, discordant for congenital spinal cervical anomalies, is described. Zygosity chances are calculated on the basis of initial dizygosity chance, sex likeness, red cell antigens, serum types, red cell enzymes, and dermatoglyphic data. The chance for monozygosity adds up to 0.9992. Literature data on cervical anomalies in twins are reviewed.

It is concluded that, although the inheritance of spinal anomalies, such as hemivertebra, is still an open question, this twin pair supports the present trend of ideas that most of these anomalies are caused by peripheral, nongenetic factors.

The first case of MZ twins concordant for oculo-auriculo-vertebral dysplasia is reported. In the light of the data from the literature concerning the etiology of the syndrome, this observation does not allow an absolute conclusion but points towards the possible existence of a genetic form of this syndrome.

Sixteen anthropometric measurements were performed on each of 48 MZ and 51 DZ adult twin pairs. The largest amount of diversity between MZ and DZ was observed in relation to stature which was in average about three-and-a half times more different in the latter. Forehead and nasal height were also three times more variable among DZ twins, while head and nasal breadth, morphological face height, and lip thickness were twice as variable. The heritability estimates and F ratios yielded significant values in both sexes for twelve traits. The exceptions were mandibular and minimum frontal breadth, calf and chest circumference. The largest heritabilities were observed for stature, head breadth and lip thickness. Correlation matrices were obtained for all measurements; those showing significantly positive coefficients, however, did not show similar heritability values.

Adenosine deaminase (ADA) isoenzymes in a Swedish population of 342 unrelated individuals have been determined according to the method of Spencer et al. (1968). The gene frequencies found were 0.9357 and 0.0643 for ADA 1 and ADA 2 respectively. These frequencies are in good accordance with previous investigations.

The application of an ammoniacal silver procedure to the staining of human metaphase chromosomes is described. A map based on the differential staining characteristics of chromosome segments is presented.

A survey has been carried out (using Quinacrine stain) on the frequency and position of an intensely fluorescent body (F-body) in the nuclei of leukocytes from peripheral blood smears in normal individuals and in the main syndromes from numerical alteration of sexual chromosomes.

Instead of the random activation and/or inactivation of the X-chromosome in sex determination, as suggested by the Lyon's hypothesis, a proposal is made here that crossingover between the sister- and/or nonsisterstrands at the sticky or nonsticky loci, at heterochromatinizing regions and at the inactivating centers of the centromère, be responsible for the heterochromatinization and/or heteropyknotization of the X-chromosome. (This proposal will be called the Mustafa hypothesis.)

Such would be the basis for the activation and/or inactivation of the X-chromatid(s), which would then replicate into a normal or a heterochromatic X-chromosome respectively. The heterochromatic X-chromosome may be transformed into a heteropyknotized mass of sex chromatin (Barr body). Translocation of the Y-chromosome and of some of the autosomes could also result in the same effect. Hence, the number of heterochromatinized X-chromosomes, and/or of heteropyknotized masses (Barr bodies), in each daughter-cell is directly proportional to half the number of chromatids involved in crossingover and/or translocation in the mother-cell.

On account of the dermatoglyphic findings in gonosomal aberrations, sex differences in dermatoglyphic structures, studied in the normal population, are interpreted on the basis of the respective gonosomal constitution.