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NITROSOGUANIDINE INDUCED MORPHOLOGICAL MUTANTS OF THE BLUE-GREEN ALGA, ANACYSTIS NIDULANS: CHARACTERIZATION AND GENETIC STUDIESHarwood, Gerald Dennis, 1936- January 1971 (has links)
No description available.
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Characterization of twenty-one mutants resistant to high levels of streptomycin in Chlamydomonas reinhardiHorn, Nancy Ann, 1949- January 1977 (has links)
No description available.
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Evolutionary and ecological interactions affecting seaweedsOlson, Annette M. 18 June 1992 (has links)
The term "interaction" in evolutionary biology and ecology
describes the relationships among variables in two classes of causal
models. In the first, "interaction" refers to the influence of a
single putatively causal variable on a variable of interest. In the
second class of models, the term applies when a third variable
mediates the relationship between two variables in the first class of
models. The development of multi-factor causal models in evolutionary
biology and ecology represents a stage in the construction of theory
that usually follows from complexities discovered in single-factor
analyses. In this thesis, I present three cases that illustrate how
results of simple single-factor models in the population genetics and
community ecology of seaweeds may be affected by incorporation of a
second causal factor.
In Chapter II, we consider how the effect of natural selection
on genetic variability in seaweeds and other plants may be mediated by
life history variation. Many seaweeds have haplodiplontic life
histories in which haploid and diploid stages alternate. Our
theoretical analysis and review of the electrophoretic literature show
that the level of genetic polymorphism in haplodiplonts is not
necessarily reduced relative to that in diploids. In Chapter III, I
take an experimental approach to understanding how herbivory may
mediate the effect of desiccation on the upper intertidal limit of a
red alga, Iridaea cornucopiae. Iridaea appears to be grazer-limited
in dry, but grazer-dependent in moist environments, suggesting that a
third factor may mediate the interaction of desiccation and herbivory.
Finally, in Chapter IV, we consider research strategies for studying
how the outcome of competitive interactions is affected by seaweed
traits. Some of the problems that arise in applying simple models of
competition to plants suggest the need for theory that explicitly
incorporates plant traits in two- (or more) factor models of
interspecific competition. In particular, we note that unique traits
of seaweeds require development of new approaches to understanding
competition.
Single-factor causal models represent an indispensable stage in
the development of evolutionary and ecological theory. Properly
conceived theoretical and empirical studies focus attention on the
assumptions under which such models will hold and suggest lines of
inquiry that ultimately lead to the integration of additional causal
factors in conceptual models of natural processes. Identifying the
circumstances under which simple models will suffice remains one of
the most important challenges of evolutionary and ecological
scholarship. / Graduation date: 1993
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Small RNA and genome interactions in Chlamydomonas reinhardtii recombinantsHessenberger, Daisy Sophia Innes January 2015 (has links)
When conspecific individuals are crossed, the ensuing hybridization creates a spectrum of phenotypes in the resulting offspring. Many of hybrid traits will be additive, similar to the parental phenotypes. In some cases however, transgressive phenotypes are formed, outside the range of that of the parental phenotypes. Transgressive phenotypes can either be restricted to the F1 generation or be heritable throughout the hybrid lineage. While the mechanism behind heritable transgressive phenotyped is yet to be determined, transgressive gene expression is thought to be the root cause of their formation. Epigenetics modifications, heritable variation separate to the DNA code, can alter gene expression, persist through generations, and vary between individuals and over time. This makes them ideal candidates to be involved in the formation of transgressive phenotypes. RNA silencing is an epigenetic mechanism of gene regulation relying on 20Q24nt single stranded small RNAs (sRNAs). Small RNAs, due to their ability to set up persistent epigenetic marks at a locus, have the potential to create heritable transgressive gene expression. For example, when genetic variation from one parental genome presents novel targets to the sRNAs of the other parental genome, new epigenetic marks such as DNA methylation or secondary sRNAs can be created at target sites. In order to understand the potential of small RNAs to influence hybrid phenotype, I designed crossing experiments with Chlamydomonas reinhardtii, choosing this unicellular alga due to the genetic tools available and the haploid nature of its vegetative cells. The specific aim of the experiment was to identify transgressively expressed sRNA populations. Crossing two geographically distinct strains of C. reinhardtii, and sequencing both the genomes and sRNAomes of parents and recombinants, I was able catalogue both genetic and epigenetic variation in the parental strains providing unique insight into the inheritance of small RNAs in this alga. In this thesis, I first compare the genomes of the parental strains, identifying polymorphisms and assessing genetic variation in RNA silencing pathway components. I then describe the sRNA profiles of the parental strains, identifying differentially expressed sRNA loci. I then describe my approach to identifying transgressively expressed sRNA loci in the hybrids. While many sRNA loci in the recombinants exhibit additive sRNA expression, I found multiple transgressively expressed sRNA loci. Using the available bioinformatics tools, I identified potential miRNAs and phased secondary sRNAs within the list of transgressively expressed loci. Target analysis of one of the transgressively expressed miRNAs linked it with the transgressive expression of certain phased loci, suggesting a potential for sRNAs to be able to set up heritable epigenetic marks in recombinant C. reinhardtii cells.
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