Showing papers in "Advances in Genetics in 1985"

Genetics, cytology and evolution of Gossypium.

Abstract: Publisher Summary This chapter presents a comprehensive review of the published information on the cytology, genetics, and evolution of Gossypium . In addition, it presents recent data and information on genome organization with which a hypothesis is proposed for the origin of the allotetraploid species that is different from that generally assumed. The genus Gossypium consists of 35 diploid species that are divided into seven genome groups and six allotetraploid species, each with the same two subgenomes. The genome relationships are also discussed in the chapter. Moreover, with the advent of the new technology of genetic engineering and its potential for improving the commercial cottons by inter- and intra- genomic transfer of desirable genetic segments, the basic genetic analyses should have even greater application in the future. The successful application of genetic engineering is greatly enhanced by the availability of fundamental knowledge of the genetic organization of the chromosomes gained through the classical genetic and cytogenetic approaches. Thus, to utilize the full potential of the new technology, it is of utmost importance that the classical approaches to the genetic analysis of the chromosomes of cotton be augmented.

Recovery, Repair, and Mutagenesis in Schizosaccharomyces pombe

Abstract: Publisher Summary This chapter presents an account of recovery, repair, and mutation processes in the fission yeast, Schizosaccharomyces pombe . Some of the aspects such as the cell cycle, macromolecular synthesis, and cell synchrony are documented to give an idea of the potential and experimental usefulness of S. pombe . In addition, the differences from S. cerevisiae are discussed, particularly as they relate to evolutionary considerations. The difference between the mitotic control of the two yeasts, Saccharomyces and Schizosaccharomyces , lies mainly in the size requirement at mitosis peculiar to S. pombe . It therefore involves some kinds of controls that are not required in budding yeasts. Furthermore, it is quite remarkable how the studies of repair and recovery using two yeasts, S. cerevisiae and S. pombe, reveal a number of important differences. The lack of photoreactivation in radiation-resistant microbes, such as S. pombe makes sense, as there may always be very efficient dark repair systems that can cope with DNA damage. Similarly, in haploid organisms where the life cycle is predominantly in G 2, the major repair system may be of the recombinational repair type.

Y chromosome function and spermatogenesis in Drosophila hydei.

Abstract: Publisher Summary This chapter elaborates spermatogenesis in Drosophila hydei and develops some working concepts for further studies. The study of spermatogenesis in D. hydei provides a particularly favorable opportunity to explore molecular events at the chromosomal level by using cytological parameters. Occurrence of Y-chromosomal lampbrush loops in D. hydei can be used as cytological markers in genetic experiments. This permits not only a more precise fine mapping of the fertility genes in the Y chromosome, but also the detection of genetic effects such as synthetic sterility and loop inactivation processes. Lampbrush loops offer a unique opportunity in the study of regulatory interactions in the eukaryotic genome. Non-Y chromosomal loci, interacting with the activity of the Y chromosome, can be recovered by isolating male-sterile mutations and by screening these mutations cytologically for effects on Y-chromosomal lampbrush loops in spermatocyte nuclei. This permits not only the recovery of loci involved in the general regulation of Y chromosomal gene activity, but also the identification of loci responsible for the production of Y-specific chromosomal proteins. Furthermore, loop morphology can serve as a tool to dissect such molecular parameters of gene activation.

Gene Transfer in Fungi

Abstract: Publisher Summary This chapter reviews data regarding the nature of evidence for gene transfer in fungi and the characterization of the transformants, and discuss the use of gene transfer as a genetic system to seek answers to several questions concerning the regulatory control and other basic mechanisms of eukaryotes. Fungi offer a unique system for the study of genetics and biochemistry of eukaryotes. Studies of fungi have been particularly important in elucidating the process of genetic recombination, and in the emergence of yeast as the major system for the cloning of a eukaryotic gene. Fungi can be cultivated and manipulated using a combination of techniques used in the study of bacteria. Fungi possess a spectrum of nuclear, organellar genetic systems. Both the nuclear and the extranuclear genetics are very well established and thus provide an unique opportunity for the characterization of the plasmid genetic elements and their interactions with the nuclear and the organellar genetic systems.

Recent Developments in Population Genetics

Abstract: Publisher Summary This chapter provides a review of several divergent areas of recent research activity in population genetics to illustrate the span of contemporary research activity in this field. The major goal of experimental population genetics is the description and analysis of genetic variation. Genetic variation is central to evolutionary theory because it governs the rate of population improvement under selection. This new approach to the study of genetic variation has advantages over all previous methods in permitting the detection of genetic differences at the level of primary DNA sequences, unconfounded by gene expression. Applied to the study of individual genes, this approach allows the construction of fine physical maps of sequence variants directly from the primary data. Consequently, genetic variants can be associated with various functional regions of a gene and statistical associations between different polymorphic sites can be investigated. On a broader scale, DNA sequence variation can be used to investigate the evolution of gene families, as well as the evolution of entire genomes, such as those of eukaryotic cell organelles.