No description available.

Xylella fastidiosa subspecies fastidiosa is the causative agent of Pierce’s disease of grape and has caused significant crop stress and loss in vineyards throughout Texas. While multiple techniques are available to identify subspecies of X. fastidiosa, only simple sequence repeat markers can be used for the differentiation of isolates within individual subspecies. In this research, SSR markers were utilized to demonstrate the diversity of subsp. fastidiosa isolates from within a single vineyard. The distributions of strains defined within subsp. fastidiosa were also compared to epidemiological data to clarify any relationships. Initial results from isolation attempts indicate disease severity to have the largest impact on the success of isolation attempts with 7% of samples rated as ‘Healthy’ and 83% of samples rated as ‘Advanced’ producing successful isolations. A conventional PCR protocol employing 5 SSR markers was used to generate banding profiles for 97 isolates collected from 7 grape varieties planted in 5 blocks throughout a single Texas vineyard. SPSS statistical program was used to execute a hierarchical cluster analysis to produce a dendrogram which grouped isolates into 3 strain groups with 7% or 15% dissimilarity. Of the 3 epidemiological factors analyzed, the distribution of strains showed significant dependence on grape variety while having no dependence on disease severity or location within the vineyard.

Made available in DSpace on 2017-07-25T19:30:51Z (GMT). No. of bitstreams: 1 Cristiane Romanek.pdf: 2518407 bytes, checksum: a9fd5d1b1e96d98a44dfc90dfaa0a4b6 (MD5) Previous issue date: 2014-12-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objectives of this study were to characterize the resistance/susceptibility of the F2:3 maize progenies to anthracnose leaf blight (Colletotrichum graminicola), to estimate the genetic parameters associated with resistance, and map the genomic regions associated with quantitative resistance loci (QRL) by means molecular markers microsatellites (SSRs) and AFLPs. The inbred lines L04-2 (resistant) and L95-1 (susceptible) were crossed to generate an F2 population. Individuals of this population were selfed resulting F2:3 progenies, these were evaluated in three trials conducted in a randomized block design, with three replications. The treatments were consisted of 121 F2:3 progenies, parental lines and F1 generation. Plants were inoculated in two times between the stages V6 and V7, the second inoculation made seven days after the first. Three evaluation of the severity of anthracnose leaf blight were conducted: the 1st in VT (flowering) stage, 2nd in R2 and 3rd in R3 through a note scale with amplitude from 1 to 6. From the point assessments, was calculated the area under the disease progress curve (AUDPC). The results showed highly significant effects for both point assessments for AUDPC, indicating high genetic variability for resistance to anthracnose leaf blight among the F2:3 progenies. The high magnitude of genetic parameters indicate that the genetic control of resistance to anthracnose leaf blight of corn is associated with the expression of genes of great phenotypic effect. QRL mapping was conducted based on phenotypic analysis of 121 F2:3 progenies, evaluated in three experiments for three point assessments and AUDPC. Linkage analysis between the markers (microsatellites and AFPLs) and QRLs was performed by analysis of multiple linear regression and by composite interval mapping. Multiple linear regression identified mark SSRs and AFPLs highly associated with resistance alleles, the E55139 and E56386 AFLPs loci with the highest partial regression coefficients for the three experiments, with amplitudes from 6,67 to 31,31 % and 6,12 to 21,78 %, respectively. Were mapped 19 QRLs to anthracnose leaf blight in eight linkage groups. Six QRLs were the most stable environments for different evaluation and responsible for the large magnitude of the phenotypic variation in resistance. The high number of QRLs mapped in this population confirms the pattern of quantitative inheritance of resistance in tropical maize to anthracnose leaf blight caused by C. graminicola. / Os objetivos deste trabalho foram caracterizar a resistência/suscetibilidade de progênies F2:3 de milho à antracnose foliar (Colletotrichum graminicola), estimar os parâmetros genéticos associados à resistência, e mapear as regiões genômicas associadas à resistência quantitativa (QRL) por meio de marcadores moleculares microssatélites (SSRs) e AFLPs. As linhagens endogâmicas L04-2 (resistente) e L95-1 (suscetível) foram cruzadas entre si a fim de gerar uma população F2. Os indivíduos desta população foram autofecundados dando origem as progênies F2:3 que foram avaliadas em três experimentos, conduzidos no delineamento de blocos casualizados com três repetições. Os tratamentos foram constituídos de 121 progênies F2:3, linhagens parentais e geração F1. As plantas foram inoculadas por duas vezes entre os estádios V6 e V7, sendo a 2ª inoculação realizada sete dias após a 1ª. Foram realizadas três avaliações da severidade da antracnose foliar: a 1ª no estádio VT (pendoamento), a 2ª em R2 e a 3ª em R3 através de uma escala de notas com amplitude de 1 a 6. A partir das avaliações pontuais, calculou-se a área abaixo da curva de progresso da doença (AACPD). Os resultados evidenciaram efeitos altamente significativos tanto para as avaliações pontuais quanto para a AACPD, indicando grande variabilidade genética para a resistência à antracnose foliar entre as progênies F2:3. As elevadas magnitudes dos parâmetros genéticos indicam que o controle genético da resistência de milho à antracnose foliar esteja associado à expressão de genes de grande efeito fenotípico. O mapeamento de QRLs foi realizado com base na análise fenotípica das 121 progênies F2:3, avaliadas em três experimentos para as três avaliações pontuais e para a AACPD. A análise de ligação entre os marcadores (microssatélites e AFPLs) e os QRLs foi efetuada por meio da análise de regressão linear múltipla e pelo mapeamento por intervalo composto. A regressão linear múltipla identificou marcas SSRs e AFPLs altamente associadas a alelos de resistência, sendo os locos AFLPs E55139 e E56386 com os maiores coeficientes de regressão parciais para os três experimentos, com amplitude de 6,67 a 31,31 % e de 6,12 a 21,78 %, respectivamente. Foram mapeados 19 QRLs à antracnose foliar em 8 grupos de ligação. Seis QRLs foram mais estáveis para os diferentes ambientes de avaliação e responsáveis por grande magnitude da variação fenotípica em resistência. O elevado número de QRLs mapeados nesta população confirma o padrão de herança quantitativa da resistência de milho tropical à antracnose foliar causada por C. graminicola.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-05-08T15:19:29Z No. of bitstreams: 2 Dissertação - Ariane Rolins de Santana - 2014.pdf: 1616629 bytes, checksum: 564437916d584de9d3769067e398b29b (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-05-08T15:37:12Z (GMT) No. of bitstreams: 2 Dissertação - Ariane Rolins de Santana - 2014.pdf: 1616629 bytes, checksum: 564437916d584de9d3769067e398b29b (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-05-08T15:37:12Z (GMT). No. of bitstreams: 2 Dissertação - Ariane Rolins de Santana - 2014.pdf: 1616629 bytes, checksum: 564437916d584de9d3769067e398b29b (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-04-10 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Microsatellite markers are widely used to assess the genetic variability in natural populations. These markers can be developed from derived Expressed sequence tag (ESTs) or genomic libraries. A feasible and economical alternative for obtaining of these markers for species that do not already have them is the transferability from primers designed for species evolutionarily close. The species Pterodon emarginatus Vogel (sucupira) belongs to the Fabaceae family and shows great potential for use timber and medicinal, which makes them a target of exploitation. Thus, studies that contribute to their use and conservation are needed, including the genetic population. Therefore, the aim of this study was to evaluate the potential for cross-amplification primers developed for the species Phaseolus vulgaris to P. emarginatus and to analyze the polymorphism of the loci transferred from multiplex genotyping in three populations of this species. For this, were evaluated 539 primers developed for Phaseolus vulgaris, with 345 derived from ESTs libraries and 194 genomics. Amplification tests were performed using three individuals, while the assessment initial of the polymorphism with eight. Finally, genetic diversity parameters were estimated using 88 plants from three natural populations of P. emarginatus. Primers that showed amplification products visualized on agarose gel were then evaluated in 6% acrylamide gel stained with silver nitrate. Polymorphic loci were synthesized with fluorescence for evaluation and genotyping by capillary electrophoresis in ABI3500 automatic DNA analyzer. The loci were transferred to P. emarginatus 23 (4 %) being 7 polymorphic. Polymorphic, 6 electropherograms profiles. These 6 loci were evaluated in populations along with three polymorphic genomic loci previously standardized sucupira, totaling nine loci suitable for genotyping. It was possible to develop two multiplex systems, a compound of 5primers and another for 4. The number of alleles per locus ranged from two to 13, with an average of five alleles per loci. The mean values of He and Ho for both populations were 0,563 and 0,463 respectively. The value of f was not significant for the total population and equal to 0,144. The values FIT and FST were significant and equal to 0,06 and 0,195 respectively. Microsatellite markers transferred and polymorphic for P. emarginatus showed polymorphism and can be used in studies genetic population more depth to the species. / Os marcadores microssatélites são amplamente utilizados para acessar a variabilidade genética em populações naturais. Estes marcadores podem ser desenvolvidos a partir de bibliotecas derivadas de Sequências Expressas Transcritas (ESTs) ou genômicas. Uma alternativa possível e econômica para a obtenção destes marcadores para espécies que ainda não os possuem, é a transferibilidade a partir de primers desenhados para espécies evolutivamente próximas. A espécie Pterodon emarginatus Vogel (sucupira) pertence à família Fabaceae e apresenta grande potencial de uso medicinal e madeireiro, o que faz dela alvo da exploração extrativista. Assim, estudos que contribuam com o seu melhor uso e conservação são necessários, dentre eles os genético-populacionais. Diante disso, o objetivo deste estudo foi avaliar o potencial de amplificação cruzada de primers desenvolvidos para a espécie Phaseolus vulgaris para P. emarginatus e analisar o polimorfismo dos locos transferidos a partir de sistema multiplex de genotipagem em três populações desta espécie. Para tanto, foram avaliados 539 primers desenvolvidos para Phaseolus vulgaris, sendo 345 derivados de bibliotecas de ESTs e 194 genômicos. Os testes de amplificação foram realizados utilizando três indivíduos, enquanto a avaliação inicial do polimorfismo com oito. Por fim, os parâmetros genéticos de diversidade foram estimados utilizando 88 plantas, provenientes de três populações naturais de P. emarginatus. Os primers que apresentaram produtos de amplificação visualizados em gel de agarose foram, posteriormente, avaliados em gel de acrilamida 6% corado com nitrato de prata. Os locos polimórficos foram sintetizados com fluorescência para a avaliação e genotipagem via eletroforese capilar, no analisador automático de DNA ABI3500. Os locos transferidos para P. emarginatus foram 23 (4%) sendo 7 polimórficos. Dos polimórficos, 6 apresentaram bons perfis de eletroferogramas. Estes 6 locos foram avaliados nas populações juntamente com três locos genômicos polimórficos previamente padronizados para sucupira, totalizando nove locos adequados para genotipagem. Foi possível o desenvolvimento de dois sistemas multiplex, um composto de 5 primers e outro por 4. O número de alelos por loco variou de dois a 13, com uma média de cinco alelos por loco. Os valores médios de He e Ho para o conjunto das populações foram de 0,563 e 0,463 respectivamente. O valor de f não foi significativo para o total das populações e igual a 0,144. Os valores de FST e FIT foram significativos e iguais a 0,06 e 0,195 respectivamente. Os marcadores microssatélites transferidos e polimórficos para P. emarginatus apresentaram bom polimorfismo e podem ser utilizados em estudos genético-populacionais mais aprofundados com a espécie.

The grain amaranths (Amaranthus hypochondriacus L., A. cruentus L., and A. caudatus L.) are important pseudocereals native to the Americas that have received increased attention for their nutritional content, specifically their balance of amino acids. The objective of this project was to produce and characterize a set of highly informative, reproducible microsatellite markers for the grain amaranths. A total of 1457 clones were sequenced from three genomic libraries enriched for the microsatellite motifs AAC, AAT and AC. Of these, 353 (24%) contained unique microsatellites. An additional 29 microsatellite loci were identified among 728 BAC-end sequences of a newly developed amaranth BAC library. Flanking primers were designed for 319 of the microsatellite loci and all were screened on a panel of diverse amaranths, including grain and weedy Amaranthus species. A total of 179 (56%) microsatellites were polymorphic across accessions from the three grain amaranths. Among these polymorphic microsatellite loci, a total of 731 alleles were identified with average of four alleles per locus. Heterozygosity values ranged from 0.14 to 0.83 with a mean value of 0.62. Thirty-seven (21%) of the markers were polymorphic between the parents of a segregating population and were shown to be inherited in a normal Mendelian fashion based on chi-squared analysis, demonstrating the utility of these markers for linkage mapping of the amaranth genome. Phylogenetic analysis using the marker data showed A. hybridus accessions in two of the three major grain amaranth clades, suggesting the polyphyletic evolution of the three cultivated species from different A. hybridus ancestors. The microsatellite markers reported here will be useful for further evaluating the relationships among the grain amaranths and their relatives and are an ideal resource for use in marker-assisted breeding programs, germplasm analysis and varietal identification. The transferability of these markers to A. hybridus, A. powellii, and A. retroflexus as reported here suggests that the markers may be useful to other species with the genus Amaranthus, including economically important weeds, vegetable amaranths, and ornamentals.

Monoploid potato genotypes represent plant material that is free from the "genetic load" of lethal and severely deleterious alleles normally present in the highly heterozygous cultivated potato species. Field evaluations enabled the identification of agronomically superior monoploid potato genotypes from a population of more than 100 anther-derived monoploids. Chemical fusion and electrofusion between pairs selected from 31 superior monoploids resulted in the production of three different groups of intermonoploid somatic hybrids. The hybridity of somatic hybrid plants and calluses was confirmed through PCR-based amplification of simple sequence repeat (SSR) sequences in the potato genome. Polymorphic SSR loci between the monoploid parents of a particular group of somatic hybrids were used to separate true somatic hybrids (heterozygous at the loci) from parental somaclones regenerating from unfused protoplasts (homozygous for one parental band at the loci). One group of somatic hybrids (SH1, SH2 and SH2B) was of particular interest because it resulted from the fusion of a S. phureja monoploid to a high acetylleptinidine-producing monoploid derived from an F1 hybrid between S. chacoense and S. phureja. The leptine acetylleptinidine (ALD) is produced only by some accessions of S. chacoense Bitt. and provides resistance to feeding by the Colorado potato beetle (Leptinotarsa decemlineata Say) when present in sufficient concentrations. The somatic hybrids produced moderate levels of ALD in leaves and stems (roughly 60% that of a high ALD-producing S. chacoense clone). Pollinations of SH1, SH2 and SH2B by several diploid and tetraploid potato clones resulted in three fruit on SH2, one fruit on SH2B and no fruit on SH1. Two resulting progeny populations of SH2 [SH2A = SH2 × S. andigena 8-1 (4x); SH2P = SH2 × S. phureja 66AP11-53 (2x)] expressed higher fertility than the original somatic hybrids and were sexually crossed as both male and female parents to S. tuberosum cv. Atlantic. All of the SH2 progeny populations expressed acetylleptinidines, albeit at lower levels than the SH2 somatic hybrid, providing strong evidence that the genes controlling acetylleptinidine production are dominant. Variation for ALD expression in the SH2 progeny indicated one or a few genes with additive effect controlling the ALD trait. In addition, the choice of male parent in sexual crosses to SH2 affected subsequent ALD expression in progeny populations. The SH2 progeny represent an important first step towards transferring acetylleptinidines to cultivated potato. SH1, SH2 and SH2B appeared to be negatively affected by an unusually high ploidy (hexaploid, 6x). Field-grown plants produced many tubers (mean = 35) of low weight (mean = 10.4 g) and were stunted in appearance. Anther culture of SH2 yielded triploid regenerants (3x). These regenerants may be more phenotypically normal than the original somatic hybrids because of lower ploidy. Segregation of SSR alleles in the triploid anther culture regenerants provided evidence that the hexaploid somatic hybrid SH2 genome is comprised of four homologous genomes of CP2-103 (the high leptine-producing monoploid) and two homologous genomes of 13-14 203 (the S. phureja monoploid). / Master of Science

No description available.

Anther-derived monoploids of Solanum phureja were utilized to investigate factors essential to an efficient method of regenerating doubled monoploids (DMs). The presence of silver thiosulfate (STS) in the MS basal medium did not affect the frequency of cells with 2x nuclei but increased the proportion of cells with 1x nuclei and decreased the proportion with 4x nuclei. Results indicated that STS lower the occurrence of endopolyploid nuclei. The production of DMs was not affected by the presence of STS in MS basal medium on which the source of leaf explants was maintained. The incubation of leaf cultures in the dark or light during the callus induction phase did not influence the subsequent regenerative ability of the monoploids. However, there was a significant genotype by incubation condition interaction. Overnight incubation on MS medium with benzyladenine (BA) pulse prior to transfer to regeneration medium did not affect regeneration. Field evaluation showed various responses of DMs in terms of growth and yield compared to their anther donors or corresponding F₁ progeny. Female fertility was observed in a majority of the DMs verifying their applicability as parental genotypes in practical breeding. Efforts to generate potato hybrids based on selection of genetically diverse parents using RAPD markers and to develop high yielding diploid potato germplasm that may be instrumental in new cultivar development were addressed. Genetic diversity among in vitro plantlets of S. phureja monoploids (which represent DM maternal genotypes) and diploid heterozygous pollinators (ID lines) was estimated using RAPD markers. Field evaluation revealed significant differences among fourteen F₁ hybrids of S. phureja DM x ID with respect to total tuber number, total tuber yield, average tuber weight and vigor. Using simple matching or Jaccard coefficients, the largest parental genetic distance was associated with the highest total tuber yield among the progenies of DM parents. Based on our results, RAPDs have the potential to facilitate the identification of diverse parents to maximize the expression of heterosis in S. phureja hybrids. SSR markers were used to analyze the genetic composition of anther-derived potato plants. Anther-derived monoploids exhibited a single allele as expected. Both homozygous and heterozygous diploids were identified. SSRs were also utilized to study allelic segregation in an F₁ population. Results of this experiment revealed Mendelian inheritance of SSR alleles. / Ph. D.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2017-10-19T19:03:18Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Lucas Rosolen de Almeida Mello.pdf: 2555328 bytes, checksum: 3d7ce3cf485cd835d38b843b7b692900 (MD5) / Made available in DSpace on 2017-10-19T19:03:18Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Lucas Rosolen de Almeida Mello.pdf: 2555328 bytes, checksum: 3d7ce3cf485cd835d38b843b7b692900 (MD5) Previous issue date: 2015-02-27 / A ordem Coleoptera é a mais diversificada entre todos os seres vivos, existindo ampla possibilidades de estudos no que diz respeito à diversidade cariotípica e aos mecanismos de diferenciação. As espécies da subtribo Oedionychina (Alticinae; Chrysomelidae) são interessantes para estudos evolutivos, pois possuem cromossomos sexuais gigantes e assinápticos durante a meiose, podendo ser considerados altamente derivados. Assim, o objetivo do presente estudo foi propor os mecanismos moleculares envolvidos no processo de diferenciação e evolução dos cromossomos sexuais em espécies do gênero Omophoita. A análise de mapeamento, utilizando sondas de DNA C0t-1 total (cinética de reassociação de DNA altamente e moderadamente repetitivo) mostrou marcações distribuídas em todos os cromossomos, especialmente nos cromossomos sexuais. A hibridação cruzada entre as espécies produziu um padrão de localização muito semelhante, evidenciando que a maior parte do genoma é compartilhada entre as espécies de Omophoita. Análise em conjunto dos resultados obtidos com bandas C, fluorocromos e C0t-1 mostram que a heterocromatina das espécies em grande parte é composta de DNA repetitivo distribuída ao longo dos cromossomos sexuais e autossomos. O mapeamento cromossômico com sondas de microssatélites (SSRs) mostrou marcações conservadas para os autossomos e diversificadas para os cromossomos sexuais, evidenciando uma diferença de composição de SSRs dos cromossomos sexuais entre as espécies. Os resultados de hibridação com clones de elementos de transposição mostraram alguns padrões semelhantes aos obtidos com SSRs, podendo indicar que ao longo do processo evolutivo das espécies esses elementos estiveram presentes no processo de diferenciação. Considerando todos os resultados, pode se propor uma diferença de constituição nos cromossomos sexuais das espécies e, desta forma, inferir que os DNAs repetitivos tiveram um papel evolutivo na diferenciação desses cromossomos na subtribo. / The order Coleoptera is the most diverse of all living beings, with a wide possibilities of studies with regards to the karyotype diversity and the mechanisms of differentiation. The species of the subtribe Oedionychina (Alticinae; Chrysomelidae) are interesting for evolutionary studies due to the giant sex chromosomes and asynaptic during meiosis, can be considered highly derivate. The objective of this study was to propose the molecular mechanisms involved in the differentiation process and evolution of sex chromosomes in the Omophoita genus. The Mapping analysis using DNA C0t-1 total (reassociation kinetics highly and moderately repetitive DNA) showed marks distributed in all chromosomes, especially in the sex chromosomes. The cross-hybridization among species produced a very similar location pattern, indicating that most of the genome is shared among species Omophoita. Analysis of the results obtained in conjunct with C-bands, fluorochromes and C0t-1 together show that the heterochromatin of the species is largely composed of repetitive DNA distributed throughout the autosomes and sex chromosomes. Chromosome mapping with microsatellite (SSRs) probes showed conserved patterns for autosomes, but diversified to sex chromosomes, showing difference in SSRs composition in the sex chromosomes, of the species. The results of hybridization with transposition element clones showed some similarities patterns to the SSRs markers, which may indicate that throughout the evolutive process of species these elements were present. Considering all results we can propose differences in the constitution of sex chromosomes of the species studied, thus, we can infer an evolutionary role of repetitive DNA in the differentiation of chromosomes in the subtribe.

Microsatellites are strings of short DNA motifs (≤6 bp) repeated in tandem across genomes of both prokaryotes and eukaryotes. In 20 years, they became popular genetic markers, successfully employed in the field of genetic mapping and gene hunting, as well as to address various biological questions at the individual, family, population and species level. However, evolutionary and demographic inferences from microsatellite polymorphism are hampered by controversy and ambiguity in the mutational processes of microsatellite sequences. Drawing on new data from genome projects, I review in Chapter 1 the concept of a microsatellite life cycle, which hypothesizes that microsatellites follow a life cycle from birth, through expansion, contraction, death and potentially resurrection. To document and understand this integrative concept of evolution, which could help improve current models of microsatellite evolution, there is an implicit need to study the evolution of microsatellites above the species level. A prerequisite of such comparative studies is therefore to find microsatellite loci that are conserved between different species. The near or full completion of many vertebrate genomes and their alignment against one another offer the ultimate approach to find genomic elements conserved over a large evolutionary scale. In Chapter 2, I present a new comprehensive method to find conserved microsatellites in whole genomes. Using the multiple-alignment of the human genome against those of 11 mammalian and five non-mammalian vertebrates, I examine the genomewide conservation of microsatellites, and challenge the general assumption that microsatellites are too labile to be maintained in distant species. In Chapter 3, I present similar results using the alignment of the newly sequenced platypus genome against those of three mammals, the chicken and the lizard, and incorporate these data into the framework created by the 17-genome analysis. This enlarged dataset was ground for attempting to reconstruct a vertebrate phylogeny from the presence/absence of microsatellites in the different genomes. Maximum parsimony analyses resulted in a tree much similar to that of the current view of the vertebrate phylogeny, while Bayesian analyses showed some discrepancies. This work opens a way for novel theoretical developments regarding the inference of ancestral states of microsatellites. In Chapter 4, I show how knowledge on conserved microsatellite sites can help for the development of a set of comparative primers useful across the Mammalia; implementing a similar protocol, nine conserved dinucleotide repeats were genotyped in 20 unrelated individuals of 18 species (nine sister species) encompassing the mammalian phylogeny, including marsupials and monotremes, and four microsatellites were sequenced in 4 individuals per species. My results emphasize conserved microsatellites as a new resource for genetic mapping and population studies. Finally, in Chapter 5, I recount the unexpected extent of structural change among mammalian orthologous microsatellites, including change of complexity, motif replacement and overall length variability. Altogether, these findings provide a comprehensive framework that may help in many areas of research, including molecular ecology, genome mapping, population genetics, and genome and microsatellite evolution.