The switching of genes from the silent to the operating condition following a rigorous temporal sequence may be called “chronology of the gene”. The succession of times and its biocybernetic mechanism are peculiar to each species, but the duration of information exhibits wide intraspecific variations between populations, families, and individuals. The highly isochronic behavior of MZ twins is proof of the existence of an individual temporal constitution.

Our previous studies have proved that the duration of each information is a property of the corresponding genotype, depending on its potential time of activity (chronon), which depends in its turn on the same genotype's energy of stability (ergon).

In terms of molecular genetics, the stability against mutation of each gene, governing its Ergon/Chronon (E/G) system, is a function of three factors:

(1) Code degeneracy, i.e., the different stability of synonyms coding for the same information through different ratios of GC and AT bases, the former being the more stable.

In the complex interactions of genetic and environmental factors, time represents a coordinate. Thus, it is only logical to consider biological phenomena and features in the three dimensions of space and in the dimension of time. Gedda and coworkers devoted much attention to the genetic aspects of various chronobiological events in man, and performed an extensive series of experiments to probe the many ramifications of gene-related timing phenomena.

Time factors in cytogenetics and neoplasia are discussed by considering chronobiological events as manifestations of interconnecting oscillatory phenomena in living systems. These phenomena, in turn, are regarded as the products of negative feedback control processes.

Subjects under discussion include satellite association, nondisjunction, C-mitotic duplication, endomitosis, endoreduplication, and delayed fertilization. The different theories of carcinogenesis are briefly reviewed and the time factor, as it applies to postulated mutational changes in neoplasia, is discussed.

Genetics deals with ordered and directed biological change in time; psychiatry with the development or the breakdown over the human life span of thought, feeling, and social adaptation. With the growing acknowl-edgement of the contribution of the genotype to mental and emotional uniqueness, it is appropriate to con-sider chronological parameters of mental disease in a genetic framework. These parameters include age of onset of illness (in turn affecting clinical characteristics), sequence of morbid signs and symptoms, length of illness, periodicity of illness, and temporal relation of clinical episodes to other biological events. Data are reviewed from twin and family studies, retrospective and ongoing, that relate such time phenomena to genetic factors in psychiatric disorder. Among the conditions to be considered are schizophrenia, manic-depressive psychosis, Huntington's chorea, karyotype abnormalities, presenile and senile disease, and the psychobiological ageing process itself.

Ten (eight MM and two FF) MZ twin pairs, with one or both schizophrenic members, have been examined. The disease was concordant in four pairs, discordant in one pair, and partly concordant in five pairs.

The time of onset was simultaneous in five pairs, but showed differences of three years in two pairs, and of one-two years in two more pairs. Concordance in the time of onset was not related to severity of the disease.

A total of 45 twin pairs (19 MZ and 26 DZ), with one or both members affected by essential Generalized Epileptic Attacks, have been drawn out of the Mendel Institute's twin file. Concordance was observed in 18: 19 MZ, but only in 3: 26 DZ twin pairs.

Analysis of the 18 MZ concordant twin pairs has shown (1) concordance of clinical form in 17 pairs, (2) concordance in the age of onset in 15 pairs, and (3) concordance of expression (frequency of generalized attacks) in 13 pairs.

Sexual development may be influenced by geographic factors (temperature, humidity, altitude, light), socioeconomic factors (nutrition, public health, family size), and genetic factors (population, familial heredity). Most of them are largely interrelated and difficult to define.

An anamnestic study has been carried out in Israel on Ashkenazi, non-Ashkenazi, and Arab women aged 19 to 60. The age of menarche appeared to be significantly different for Ashkenazi vs. non-Ashkenazi, while no significant difference was found between Arabs and either of the two Jewish groups. Highly significant differences were found for the length of the menstrual cycle, although this finding should be considered with caution. No significant relationship was found between age of menarche and length of the menstrual cycle.