The Evolving Definition of the Term "Gene".

This paper presents a history of the changing meanings of the term "gene," over more than a century, and a discussion of why this word, so crucial to genetics, needs redefinition today. In this account, the first two phases of 20th century genetics are designated the "classical" and the "neoclassical" periods, and the current molecular-genetic era the "modern period." While the first two stages generated increasing clarity about the nature of the gene, the present period features complexity and confusion.

[New possibilities will open up in human gene therapy].

Gene therapy is divided into somatic and germ line therapy. The latter involves reproductive cells or their stem cells, and its results are heritable. The effects of somatic gene therapy are generally restricted to a single tissue of the patient in question.

The Development of Genetics in the Light of Thomas Kuhn's Theory of Scientific Revolutions.

The concept of a paradigm is in the key position in Thomas Kuhn's theory of scientific revolutions. A paradigm is the framework within which the results, concepts, hypotheses and theories of scientific research work are understood. According to Kuhn, a paradigm guides the working and efforts of scientists during the time period which he calls the period of normal science.

A comparison of biological and cultural evolution.

This review begins with a definition of biological evolution and a description of its general principles. This is followed by a presentation of the biological basis of culture, specifically the concept of social selection. Further, conditions for cultural evolution are proposed, including a suggestion for language being the cultural replicator corresponding to the concept of the gene in biological evolution.

The birth and development of the DNA theory of inheritance: sixty years since the discovery of the structure of DNA.

The development of the DNA theory of inheritance culminated in the publication of the molecular structure of DNA 60 years ago. This paper describes this development, beginning with the discovery of DNA as a chemical substance by Friedrich Miescher in 1869, followed by its basic chemical analysis and demonstration of its participation in the structure of chromosomes. Subsequently it was discovered by Oswald Avery in 1944 that DNA was the genetic material, and then Erwin Chargaff showed that the proportions of the bases included in the structure of DNA followed a certain law.

Evidence based on studies of the mus309 mutant, deficient in DNA double-strand break repair, that meiotic crossing over in Drosophila melanogaster is a two-phase process.

The mus309 gene in Drosophila melanogaster encodes a RecQ helicase which is involved in DNA double-strand break (DSB) repair and specifically in the choice between the different pathways of the repair. In a brood pattern analysis of mus309 and wild type females which either had or had not experienced a temperature shock, different parameters of meiotic crossing over including map distances and crossover interference in the X chromosome were measured. The results suggest that, like in other eukaryotes studied, the control of meiotic crossover formation also in D.

The effect of the mus309 mutation, defective in DNA double-strand break repair, on crossing over in Drosophila melanogaster suggests a mechanism for the centromere effect of crossing over.

The mus309 gene in Drosophila melanogaster encodes a RecQ helicase which is involved in DNA double-strand break (DSB) repair. In a brood pattern analysis, it was observed that in mus309 mutant females, the frequency of single crossovers in the central cv-v interval of the X chromosome was reduced in young females but returned to the level of the wild type control as the females aged. In the proximal v-f interval, the frequency of single crossovers was increased during the entire experimental period.

The effect of the mus309 mutation, defective in DNA double-strand break repair, on crossing over in Drosophila melanogaster suggests a mechanism for interference.

The mus309 gene in Drosophila melanogaster encodes a RecQ helicase which is involved in DNA double-strand break (DSB) repair. In a brood pattern analysis, it was observed that in mus309 mutant females, the frequency of single crossovers in the central cv - v interval of the X chromosome was decreased in young females but returned to the level of the wild type control as the females aged. In the proximal v - f interval, the frequency of single crossovers was increased during the whole experimental period.

The elusive concept of the gene.

In recent years geneticists have witnessed many significant observations which have seriously shaken the traditional concept of the gene. These specifically include the facts that (1) the boundaries of transcriptional units are far from clear; in fact, whole chromosomes if not the whole genome seem to be continuums of genetic transcription, (2) many examples of gene fusion are known, (3) likewise many examples of so-called encrypted genes are known in the organelle genomes of microbial eukaryotes and in prokaryotes, and (4) in addition to the structure of the gene, its functional status can also be inheritable, and, further, (5) epigenetic extra-genomic modes of inheritance, called genetic restoration, seem to be a rather common phenomenon, meaning that organisms can sometimes rewrite their DNA on the basis of RNA messages inherited from generations past. I will briefly review these observations and discuss the difficulties of defining the gene, and then formulate a new view, which is called the relational or systemic concept of the gene.

Evolution of man in the light of molecular genetics: a review. Part II. Regulation of gene function, evolution of speech and of brains.

In the first part of this review the evolutionary history and genomics of the human species were considered in the light of molecular genetic evidence. In this second part the emphasis will be put on the regulation of the function of the genes and evolution of the human-specific traits such as enormously large brains and the capacity to communicate with a spoken language. The age-old question of what specifically makes us humans is also dealt with in its new lightning of molecular genetics of the genome era.

Evolution of man in the light of molecular genetics: a review. Part I. Our evolutionary history and genomics.

The discovery in the mid 1970s of efficient methods of DNA sequencing and their subsequent development into more and more rapid procedures followed by sequencing the genomes of many species, including man in 2001, revolutionised the whole of biology. Remarkably, new light could be cast on the evolutionary relations of different species, and the tempo and mode of evolution within a given species, notably man, could quantitatively be illuminated including ongoing evolution possibly involving also the size of the brains. This review is a short summary of the results of the molecular genetic investigations of human evolution including the time and place of the formation of our species, our evolutionary relation to the closest living species relatives as well as extinct forms of the genus Homo.

mus309 mutation, defective in DNA double-strand break repair, affects intergenic but not intragenic meiotic recombination in Drosophila melanogaster.

The effect was investigated of the hypomorphic DNA double-strand break repair, notably synthesis-dependent strand annealing, deficient mutation mus309 on the third chromosome of Drosophila melanogaster on intergenic and intragenic meiotic recombination in the X chromosome. The results showed that the mutation significantly increases the frequency of intergenic crossing over in two of three gene intervals of the X chromosome studied. Interestingly the increase was most prevalent in the tip of the X chromosome where crossovers normally are least frequent per physical map unit length.

General outlines of the molecular genetics of the Notch signalling pathway in Drosophila melanogaster: a review.

The Notch signalling pathway appears to be ubiquitous in virtually all cell-cell contacts in all metazoan animals, and is best known and most throughout studied in Drosophila melanogaster. In this species the Notch signalling pathway regulates, with both positive and negative signals, the differentiation of at least central and peripheral nervous system and eye, wing disc, oogenesis, segmental appendages such as antennae and legs, and muscles, through lateral inhibition or induction. In general, the pathway works as follows: Notch is most likely a dimeric transmembrane receptor at the cell surface, where it is activated by its ligands Serrate and or Delta from the neighbouring cell Fringe, discriminating between the two ligands.

Historical development of the concept of the gene.

The classical view of the gene prevailing during the 1910s and 1930s comprehended the gene as the indivisible unit of genetic transmission, genetic recombination, gene mutation and gene function. The discovery of intragenic recombination in the early 1940s led to the neoclassical concept of the gene, which prevailed until the 1970s. In this view the gene or cistron, as it was now called, was divided into its constituent parts, the mutons and recons, materially identified as nucleotides.

Analysis of morphogenetic movements in the development of the notum anlage of Drosophila melanogaster.

A comparison of the morphogenetic maps of the notum anlage of Drosophila melanogaster derived from the gynandromorph data and mosaics induced by somatic crossing-over during the first instar larval stage revealed that practically no major morphogenetic movements occur in the development of the anlage between the blastoderm and first instar larval stages and the adult stage. By comparing the morphogenetic map derived from gynandromorphs and the fate map derived from data on the transplantation of fragments of the mature wing imaginal disc, it was observed that no major morphogenetic movements occur in the notum anlage between the stages of the allocation of the disc and the mature disc. The results are consistent with the observations of other authors concerning the larval development of eye-antenna, wing and leg discs.

Fine structure of flight muscles in different Notch mutants of Drosophila melanogaster reared at different temperatures.

The fine structure of the indirect flight muscles was studied by electron microscopy in the following Notch locus mutants of Drosophila melanogaster reared at 18° C or 29° C for 6 days after eclosion: Ax /Ax, Ax/ Ax, l(1)N/l(1)N,l(1)N/Y and in wild-type controls. The flies were raised up to eclosion at 25° C or 18° C. It was observed that the l(1)N flies gradually became flightless within a few days if reared at 29° C as adults, and gross changes in the fine structure of the flight muscles were also observed in flies of this genotype.