STM Article Repository

The independent hereditary factors, such as Mendelian genes, are not sufficient for the existence and operation of genetic systems. The hereditary factors of a different type were searched for. A new class of mutations, referred to as conditional mutations, was discovered in Drosophila melanogaster. Such a mutation dies in a restrictive genotype but survives and reproduces in a permissive genotype. Besides their conditional nature, mutations in a permissive genotype display a set of specific features that drastically distinguish them from conventional mutations, namely, they are (1) dominant; (2) as a rule, lethal; (3) drastically decrease fertility; (4) interact with chromosomal rearrangements; (5) switch the genome from a stable to an unstable state; (6) increase the basal metabolism; (7) induce modifications and morphoses; (8) their manifestation is inherited in a parental manner. The total number of experiments was performed from 2000 to recover conditional mutations in D. melanogaster is 8. As a result, 60 conditional dominant lethals were identified in the X chromosome, 10 in chromosome 2, and 4 in chromosome 3. Six mutations had visible phenotypes.

Four properties of these mutations—conditional manifestation together with (1), (4), and (8) suggest that the mutant genes (1) are segments of DNA, (2) their products are RNA duplexes (3) active in germ cells and (4) repeated in the genome. The emergence of morphoses in mutants suggests that the genes are involved in the control of ontogeny. Correspondingly, these genes were named ontogenes. Thus, the genetic system comprises the genes working according to a DNA–RNA–protein script and the ontogenes following a DNA–RNA script. The first entity is engaged in the production of the "building material" for the organism, proteins, while the second entity controls this process during the preparation of the individual developmental program. These different functions of genes depend on the type of transcript formed from DNA as well as the time and place of its origin in DNA. In conclusion, three independent lines of evidence suggest that an enigmatic class of non-Mendelian genes (ontogenes) is present in the genome: first, efficient screening tools and the resulting collections of mutants; second, highly unusual properties of the obtained mutations; and third, unusual temporal and tissue specificities of when these mutations work.