Stadler Genetics Symposia, volume 14, 1982 (MU)

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https://hdl.handle.net/10355/67073

Contents of volume 14

Acknowledgements
Contents
Douglas E. Berg, John B. Lowe, Chihiro Sasakawa and Lyn McDivitt: THE MECHANISM AND CONTROL OF Tn5 TRANSPOSITION
Edward H. Coe, Jr., Deborah L. Thompson and Virginia Walbot: NUCLEAR GENES AND CHLOROPLAST MODIFICATIONS IN MAIZE
Carol L. Dieckmann and Louise K. Pape: NUCLEAR CONTROL OF THE EXPRESSION OF THE CYTOCHROME b GENE IN YEAST MITOCHONDRIAL DNA
Henry Huang and Lee Hood: THE ONTOGENETIC AND EVOLUTIONARY ORIGINS OF ANTIBODY DIVERSITY
Ky Lowenhaupt, Michael A. Keene, Iain L. Cartwright and Sarah C. R. Elgin: CHROMATIN STRUCTURE OF EUKARYOTIC GENES: DNase I HYPERSENSITIVE SITES
Laszlo Orosz: BACTERIOPHAGE 16 - 3 OF Rhizobium meliZoti, AND ITS PATTERN OF RECOMBINATION
S. J. Peloquin: MEIOTIC MUTANTS IN POTATO BREEDING
Fred Sherman, John I. Stiles, Linda R. Friedman, Joachim F. Ernst and Gary L. McKnight: DIVERGENT AND CONCERTED EVOLUTION OF THE TWO REGIONS EMCOMPASSING THE ISO-1-CYTOCHROME c AND ISO-2-CYTOCHROME c GENES OF YEAST
Mary Collins, Robert Levis, Roger Karess and Gerald M. Rubin: A MOLECULAR ANALYSIS OF THREE UNSTABLE ALLELES IN Drosophila
Cumulative Contents of the Proceedings of the Stadler Genetics Symposia

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Stadler Genetics Symposia, volume 14, 1982 : Preliminaries and back matter
(University of Missouri, Agricultural Experiment Station, 1982) Stadler Genetics Symposium (14th : 1982 : Columbia, Missouri)
Divergent and concerted evolution of the two regions encompassing the iso-1- cytochrome c and iso-2-cytochrome c genes of yeast : (saccharomyces cerevisiae, cytochrome c of yeast, evolution of yeast, cloning yeast genes, recombinant DNA, transpositions, composite genes)
(University of Missouri, Agricultural Experiment Station, 1982) Sherman, Fred; Stiles, John I.; Friedman, Linda R.; Ernst, Joachim F.; McKnight, Gary L.; Stadler Genetics Symposium (14th : 1982 : Columbia, Missouri)
The yeast Saccharomyces cerevisiae contains a cluster of three genes CYC1-0SM1-RAD7, denoted COR, located on the right arm of chromosome X and a cluster of three genes ANP1-RAD23 -C YC7, denoted ARC, located on the left arm of chromosome V. Both COR and ARC are in approximately 6 kb long regions and there are striking similarities between CYCl and CYC7, between OSMl and ANP1 and between RAD7 and RAD23. The relationships between COR and ARC suggest that one of the regions arose during evolution by a transposition in which a circular intermediate containing the three genes integrated at a new chromosomal position. The order of the genes could have been altered if the circle closed and opened at different sites during the excision and integration, respectively. Subsequently, the primordial COR and ARC genes could have acquired slightly different properties or functions by divergent evolution. The hypothetical transposit ion that occurred during evolution superficially resembles transpositions observed in certain COR2 strains in which segments containing the entire COR region are transposed to various positions on different chromosomes. In addition to the evolutionary development by means of transpositions and divergencies, identical short stretches observed within the CYCl and CYC7 genes, as well as in other duplicated genes from yeast and other organisms, suggest the occurrence of concerted evolution. The possibility of concerted evolution has been directly demonstrated with the formation of the so-called composite genes, in which the central portions of the CYCl locus is replaced with a corresponding segment from the CYC7 locus by gene conversion. Thus, by considering the structures of the COR and ARC regions, we suggest that these two regions developed by three evolutionary processes: a transposition, divergent evolution and concerted evolution. The transposition of COR regions and the formation of CYC1-CYC7 composite genes superficially resemble two of the evolutionary steps.
Meiotic mutants in potato breeding : (haploids, 2n gametes, germplasm transfer)
(University of Missouri, Agricultural Experiment Station, 1982) Peloquin, S. J.; Stadler Genetics Symposium (14th : 1982 : Columbia, Missouri)
Three factors provide unusual opportunities for potato improvement: (1) The wild and cultivated tuber-bearing relatives of the potato represent a large source of valuable germplasm. This genetic diversity can be incorporated into commercial cultivars. The gemzplasm is valuable in providing both specific desirable traits, such as disease and insect resistance, and for broadening the genetic base; (2) Haploids (2n=24) of cultivars (2n=48) can be readily obtained and used. They offer the advantages of simpler inheritance patterns (disomic vs. tetrasomic), and more important, a direct approach to germplasm transfer from the numerous 24-chromosome, tuber-bearing relatives of the potato. They provide us with a unique means of capturing genetic diversity; and (3) The discovery of meiotic mutants which give rise to 2n gametes provide unique and exciting opportunities to increase yield and genetic diversity. It is estimated that 2n gametes formed by first division restitution (FDR) transfer intact 80 percent of the genotype of diploids to their tetraploid progeny in 4x-2x and 2x-2x crosses. The meiotic mutant parallel spindles (ps) is an FDR mechanism that accomplishes this transfer in the production of 2n pollen. Recently, two new meiotic mutants, sy2 and sy3, have been discovered. They prevent normal crossing over, and thus the result is mainly univalents at metaphase I and high male sterility. However, when a synaptic mutant is combined with the parallel spindles mutant, fertile 2n pollen is produced. The genetic significance of this combination of meiotic mutants is that it makes possible the incorporation of the intact genotype of the parent into the gamete. Thus, a truly exceptional opportunity is possible - transmitting 100[percent] of the heterozygosity and epistasis of the parent to the offspring. The meiotic mutants provide, therefore, a powerful breeding method for maximizing heterozygosity and epistasis, and a very efficient method of transferring germplasm from diploids to tetraploids.
Bacteriophage 16-3 of Rhizobium meliloti and its pattern of recombination : (Rhizobium, phage - vector, recombination)
(University of Missouri, Agricultural Experiment Station, 1982) Orosz, Laszlo; Stadler Genetics Symposium (14th : 1982 : Columbia, Missouri)
Chromatin structure of eukaryotic genes : DNase I hypersensitive sites
(University of Missouri, Agricultural Experiment Station, 1982) Lowenhaupt, Ky; Keene, Michale A.; Cartwright, Ian L.; Elgin, Sarag C. R.; Stadler Genetics Symposium (14th : 1982 : Columbia, Missouri)
We have recently learned much about the organization of the eukaryotic genome by using nucleases as probes of the protein - DNA interactions of chromatin. In this paper we review the available information from our laboratory and others concerning the DNase I hypersensitive sites of chromatin. Such sites have been found at or near the 5' ends of many genes. Frequently there is a cluster of these sites before a given gene. In addition, a number of sites have been observed which are not 5' to any known transcript; these may play roles in DNA replication or gene rearrangement. The 5' DNase I hypersensitivesites appear during development before a given gene is expressed. In several cases these events are closely temporally linked, but in some instances 5' DNase I hypersensitivesites are apparent long before a gene is due to be transcribed. For example, many sites observed in the post-blastula embryo of Drosophila are established in the pre-plastula stage. Themolecular nature of DNase I hypersensitive sites is unclear. In some instances sites have been shown to be nucleosome free regions; however the pattern of association or proteins, if any, as well as the form of the DNA molecule, remain to be established.

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