[Parental effects of conditional mutations and their explanations].

A study of the properties of conditional dominant and recessive lethals in Drosophila melanogaster has demonstrated parental effects in the inheritance and manifestation of these mutations. Maternal and paternal effects are present when conditional mutations interact with (1) one another, (2) the Y chromosome, or (3) chromosomal rearrangements, as well as (4) when the visual expression of a conditional mutation is inherited or (5) during the formation ofmorphoses (monstrosities) in mutant offspring. The maternal and paternal effects do not exclude one another: the same mutation can display both patterns. The characters manifesting themselves at late developmental stages (morphoses) are inherited according to a parental effect pattern. A general concept of the parental effect is proposed and its types are classified.

[Changes in the energy status of Drosophila as a result of genetic mutation].

Conditional dominant lethals (CDL) represent a special class of genetic mutations observed in Drosophila. Mutation manifests as a dominant allele in one genotype, but lethality is not expressed in another genotype. CDL mutants exhibit a set of traits discriminating them from classic mutations. We observed unusually high mobility of flies and high sexual activity of males carrying these mutations. We used special tests for evaluation of energy metabolism of CDL mutants. Indirect calorimetry (CO2 excretion measurement) has been used for estimation of energy exchange in four mutant and two control fly lines. A Special device has been used for evaluation of locomotor activity of these fly lines. Energy exchange and locomotor activity in CDL mutants were significantly higher than in control lines. We conclude that some genetic mutations are capable of increasing energy dissipation in their carriers.

[Conditional lethal mutations shift the genome from stability to instability].

The phenomenology of genomic destabilization is described in Drosophila melanogaster mutants containing radiation-induced conditional dominant lethals in the X chromosome and in autosome 2. Destabilization manifests itself as (1) the loss or decrease of lethality of previously lethal mutations; (2) the loss of expression of visible dominant mutations in an opposite homolog; (3) chromosomal instability resulting in the loss of the X chromosome in germline and somatic cells; (4) the occurrence of novel mutations (secondary mutagenesis); (5) the occurrence of single and mass modifications; (6) disturbances in individual development (formation of morphoses). The key event for the shift of the genome from the stable state into the unstable one is the occurrence of a conditional dominant lethal mutation.

A novel type of gene interaction in D. melanogaster.

The genes interact according to classical mechanisms, namely, complementation, modification, polymery, and epistasis, in the cells and organisms carrying these genes. Here we describe a novel type of gene interaction when the interacting genes reside in parents, whereas the interaction event takes place in their progenies lacking these genes. The conditional mutations in the D. melanogaster male X chromosome caused the "prohibition on producing daughters" in its offspring. The chromosomal rearrangements in chromosomes 2 and 3 of its female partner removed the prohibition. The phenomena of "prohibition" and "removal of prohibition" appeared as a parental effect in both the male and female. Both phenomena ensued from the presence of the studied mutations in parents rather than their unviable or survived progenies. Thus, the gene interaction when the genes themselves are absent at the site of interaction and during the interaction event takes place in drosophila.

[Genes controlling ontogenesis: morphosis, phenocopies, dimorphs, and other visible expressions of mutant genes]. / Geny, upravliaiushchie ontogenezom: morfozy, fenokopii, dimorfy i drugie vidimye proiavleniia mutantnykh genov.

We studied facultative dominant lethal mutations obtained earlier in Drosophila melanogaster. In some genotypes, these mutations were expressed as lethals, but in other genotypes they lacked this expression. The mutations were maintained in the following cultures: (1) females Muller-5 heterozygous for the mutation; (2) males crossed to attached-X females; and females and males homozygous for the mutation. During culturing, many mutations were found to give rise to phenotypically abnormal progeny. Generally, these abnormalities were morphoses involving various body parts; they were mostly asymmetric and non-heritable. Maternal and paternal effects in the formation of morphoses were observed. In four cases, dimorphic mutations were recorded: a female homozygous for the mutation had mutant phenotype whereas its male counterpart was phenotypically normal. The mutations were recessive with regard to the norm. New phenotypes behaving as mutations with incomplete penetrance arose during culturing. In cultures of mutant homozygotes phenocopies would appear en masse; they would persist for one or two generations and disappear. One wave of phenocopies succeeded another. Visible phenotypes appeared, which further behaved as ordinary recessive mutations. We concluded that these visible manifestations are characteristic for regulatory mutations controlling ontogeny. Their appearance is explained by the activation of new regulatory scenarios caused by blocking standard regulatory pathways.

[The main effect of chromosomal rearrangement is changing the action of regulatory genes]. / Glavnoe deistvie khromosomnoi perestroiki--izmenenie raboty reguliatornykh genov.

Effect of chromosomal rearrangements on the expression of mutations was studied in Drosophila melanogaster regulatory genes. These were facultative dominant lethals and recessive lethals on the X chromosome obtained by the classical Muller-5 method. Chromosomal rearrangements drastically changed the expression of regulatory gene mutations. Rearrangements either caused the lethal effect of mutations or suppressed the already present lethality. The action of rearrangements exhibited the maternal or paternal effect. Irrespective of the presence in the genome of mutations at regulatory genes, a rearrangement acted as a factor decreasing fertility of the organism. The rearrangement effect is identical to the expression of regulatory genes per se. It is concluded that the chromosomal rearrangement affects the examined regulatory genes indirectly through a change in the operation of regulatory genes located within the rearrangement. Thus, rearrangements gain great importance for the definition of the pattern of genome functional activity. Widespread distribution of rearrangements in individual genotypes and their effectivity in the process of speciation are thus explained.

[From genetics of intraspecific differences to genetics of intraspecific similarity]. / Ot genetiki vnutrividovykh otlichii k genetike vnutrividovogo skhodstva.

Based on the Mendelian approach to heredity, modern genetics describes inheritance of characters belonging to the category of intraspecific difference. The other large category of characters, intraspecific similarity, stays out of investigation. In this review, the genome part responsible for intraspecific similarity is considered as invariant and regulatory. An approach to studying the invariant part of the Drosophila melanogaster genome is formulated and the results of examining this genome part are presented. The expression of mutations at genes in the invariant genome part is different from that of Mendelian genes. We conclude that these genes are present in the genome in multiple copies and they are functionally haploid in the diploid genome. Severe abnormalities of development appearing in the progeny of mutant parents suggest that the mutant genes are genes regulating ontogeny. A hypothesis on an elementary ontogenetic event is advanced and the general scheme of ontogeny is presented. A concept on two types of gene allelism (cis- and trans-allelism) is formulated. This approach opens a possibility for studying genetic material responsible for the formation of intraspecific similarity characters at different taxonomic levels on the basis of crossing individuals of the same species.