Stadler Genetics Symposia, volume 15, 1983 (MU)

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Contents of volume 15

Acknowledgements
Contents
C. N. Law, J. W. Snape and A. J . Worland: CHROMOSOME MANIPULATION AND ITS EXPLOITATION IN THE GENETICS AND BREEDING OF WHEAT
H. Stern and Y. Hotta: MEIOTIC ASPECTS OF CHROMOSOME ORGANIZATION
D. L. Hartl and D. S. Haymer: MEASURES OF FITNESS IN Drosophila
R. Broglie, G. Coruzzi, G. Lamppa, B. Keith and N. Chua: MONOCOT AND DICOT GENES ENCODING THE SMALL SUBUNIT OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE: STRUCTURAL ANALYSIS AND GENE EXPRESSION
H. A. McQuade and A. M. Young- Rottler: SOME NOTES ON PREMEIOCYTES IN WHEAT
A. R. Hallauer, W. A. Russell and O. S. Smith: QUANTITATIVE ANALYSIS OF IOWA STIFF STALK SYNTHETIC
R. L. Phillips, A. S. Wang and R. V. Kowles MOLECULAR AND DEVELOPMENTAL CYTOGENETICS OF GENE MULTIPLICITY IN MAIZE
B. S. Sears: GENETICS AND EVOLUTION OF THE CHLOROPLAST
Cumulative Contents of the Proceedings of the Stadler Genetics Symposia

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Stadler Genetics Symposia, volume 15, 1983 : Preliminaries and back matter
(University of Missouri, Agricultural Experiment Station, 1983) Stadler Genetics Symposium (15th : 1983 : Columbia, Missouri)
Stadler Genetics Symposia : contents, volumes 1-15 (1971-1983)
(University of Missouri, Agricultural Experiment Station, 1983) Stadler Genetics Symposium
Contents of the proceedings of the Stadler Genetics Symposia, 1971-1983.
Meiotic aspects of chromosome organization : (meiosis, pachytene DNA)
(University of Missouri, Agricultural Experiment Station, 1983) Stern, Herbert; Hotta, Yasuo; Stadler Genetics Symposium (15th : 1983 : Columbia, Missouri)
Homologous chromosome pairing regulates the expression of a set of metabolic activities that is unique to the zygotene-pachytene interval , These activities probably relate to crossing-over and they involve specific proteins and specific chromosome regions. The recombination-related proteins include an endonuclease, a DNA-unwinding protein, and are association protein. These proteins act primarily on specific DNA sequences, their activity being manifest in the formation of nicks and gaps accompanied by repair synthesis. The site specificity of nick-repair activity is determined by site specific changes in chromatin organization. These changes do not occur in the absence of homologous pairing. The DNA undergoing nick-repair is housed in a set of families of moderately repeated sequences ("P-DNA"). They range in length from 800-4000 bp; they show very small sequence divergence and share homology with corresponding repeats across a broad phylogenetic spectrum. They are unevenly distributed in the genome. About 60% of the Lilium genome has no P-DNA sequences within at least 350 kb from one another; the remainder of the genome has P-DNA sequences spaced 30-350kb apart. Nick-repair activity is mainly confined to the end regions of P-DNA ("PsnDNA") which measure 125-400 bp in length . PsnDNA is housed in chromatin of distinctive composition. The chromatin has little, if any, histones; instead, the DNA is associated with a snRNA ("PsnRNA") and a non-histone protein. The PsnRNA is complementary to the PsnDNA and the protein binds specifically to PsnRNA. A model is briefly discussed to account for the regulation of pachytene DNA metabolism.
Genetics and evolution of the chloroplast : (cytoplasmic inheritance, nucleus-cytoplasm interaction, plastome recombination, plastome mutator, oenothera)
(University of Missouri, Agricultural Experiment Station, 1983) Sears, Barbara B.; Stadler Genetics Symposium (15th : 1983 : Columbia, Missouri)
As a photosynthetic organelle and as the site of several important biosynthetic pathways, the chloroplast is essential to the survival of the plant cell. In evolutionary terms, the chloroplast genetic material can be considered conservative: from the green algae to higher plants, chloroplast DNAs have similar sizes, gene contents and arrangements, although some modifications of the chloroplast DNA have occurred as it has coevolved with the nucleus. Mutation and recombination are traditionally considered responsible for evolutionary change, but these may be quite limited in the chloroplast genetic system. Gene conversion may result in the elimination of new mutations, while the widespread occurrence of uniparental inheritance of chloroplasts reduces the likelihood of two different plastids meeting and their DNAs recombining. In other systems, transposons contribute to genetic change. One possible explanation for plastid mutator genes is that they activate transposable elements in the chloroplast DNA. Among diverse genera in primitive and higher plants, both uniparental and biparental transmission of chloroplasts occur in sexual crosses. When maternal inheritance of plastids occurs, the paternal plastids may be excluded or eliminated from the male gamete in a variety of ways. Thus maternal inheritance has probably appeared in the algae, mosses, ferns, gymnosperms, and angiosperms through parallel evolution.
Molecular and developmental cytogenetics of gene multiplicity in maize : maize, cytogenetics, ribosomal RNA, endosperm, gametes
(University of Missouri, Agricultural Experiment Station, 1983) Phillips, R.L.; Wang, A.S.; Kowles, R.V.; Stadler Genetics Symposium (15th : 1983 : Columbia, Missouri)
Gene multiplicity alterations may be an important feature of maize developmental biology. A developmentally-phased change in DNA level has been found to be a striking feature of maize endosperm growth. I n the central portion of the endosperm tissue, an average DNA level of 4.5C during the first 10days post-pollination increases to an average of 90C by day 16.The ribosomal DNA (rDNA) proportion increases by 50 percent from day 12 to day 16 and returns to near initial levels by day 20. We propose that the rDNA replicates more rapidly than the majority of the non-rDNA regions between 12 and 1 6 days post pollination; subsequently the rDNA proportion decreases due to proportionately higher replication of other DNA. Various experimentally-induced modulations in ribosomal RNA gene multiplicity were achieved using 25 chromosomal interchanges each with a break in the nucleolus organizer region (NOR). Gametes which apparently have retained only 1-2 percent of the rDNA region were transmissible through the ovules. This finding raises the question whether gametes would be viable with nor RNA genes at the NOR. Molecular cytogenetic analyses lend support to the concept that maize development may be controlled in part by the multiplicity of specific genes.

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