RESUMO
The Afrotropical mosquito Anopheles gambiae sensu stricto, a major vector of malaria, is currently undergoing speciation into the M and S molecular forms. These forms have diverged in larval ecology and reproductive behavior through unknown genetic mechanisms, despite considerable levels of hybridization. Previous genome-wide scans using gene-based microarrays uncovered divergence between M and S that was largely confined to gene-poor pericentromeric regions, prompting a speciation-with-ongoing-gene-flow model that implicated only about 3% of the genome near centromeres in the speciation process. Here, based on the complete M and S genome sequences, we report widespread and heterogeneous genomic divergence inconsistent with appreciable levels of interform gene flow, suggesting a more advanced speciation process and greater challenges to identify genes critical to initiating that process.
Assuntos
Anopheles/genética , Especiação Genética , Genoma de Inseto , Animais , Anopheles/classificação , Evolução Molecular , Feminino , Fluxo Gênico , Masculino , Modelos Genéticos , Polimorfismo de Nucleotídeo ÚnicoAssuntos
Cromossomos Humanos Par 7/genética , Variação Genética , Pseudogenes , Sequência de Bases , Mapeamento Cromossômico , DNA Complementar/genética , Genoma Humano , História do Século XX , História do Século XXI , Projeto Genoma Humano/história , Humanos , Dados de Sequência Molecular , Pesquisa/história , Homologia de Sequência do Ácido NucleicoRESUMO
The human genome is by far the largest genome to be sequenced, and its size and complexity present many challenges for sequence assembly. The International Human Genome Sequencing Consortium constructed a map of the whole genome to enable the selection of clones for sequencing and for the accurate assembly of the genome sequence. Here we report the construction of the whole-genome bacterial artificial chromosome (BAC) map and its integration with previous landmark maps and information from mapping efforts focused on specific chromosomal regions. We also describe the integration of sequence data with the map.
Assuntos
Mapeamento de Sequências Contíguas , Genoma Humano , Cromossomos Artificiais Bacterianos , Clonagem Molecular , Impressões Digitais de DNA , Duplicação Gênica , Humanos , Hibridização in Situ Fluorescente , Sequências Repetitivas de Ácido NucleicoRESUMO
Theory is developed for the process of sequencing randomly selected large-insert clones. Genome size, library depth, clone size, and clone distribution are considered relevant properties and perfect overlap detection for contig assembly is assumed. Genome-specific and nonrandom effects are neglected. Order of magnitude analysis indicates library depth is of secondary importance compared to the other variables, especially as clone size diminishes. In such cases, the well-known Poisson coverage law is a good approximation. Parameters derived from these models are used to examine performance for the specific case of sequencing random human BAC clones. We compare coverage and redundancy rates for libraries possessing uniform and nonuniform clone distributions. Results are measured against data from map-based human-chromosome-2 sequencing. We conclude that the map-based approach outperforms random clone sequencing, except early in a project. However, simultaneous use of both strategies can be beneficial if a performance-based estimate for halting random clone sequencing is made. Results further show that the random approach yields maximum effectiveness using nonbiased rather than biased libraries.
Assuntos
Clonagem Molecular/métodos , Análise de Sequência de DNA/métodos , Mapeamento de Sequências Contíguas , Biblioteca Genômica , Humanos , Modelos Genéticos , Distribuição de Poisson , Análise de Sequência de DNA/estatística & dados numéricosRESUMO
Arabidopsis thaliana has emerged as a model system for studies of plant genetics and development, and its genome has been targeted for sequencing by an international consortium (the Arabidopsis Genome Initiative; http://genome-www. stanford.edu/Arabidopsis/agi.html). To support the genome-sequencing effort, we fingerprinted more than 20,000 BACs (ref. 2) from two high-quality publicly available libraries, generating an estimated 17-fold redundant coverage of the genome, and used the fingerprints to nucleate assembly of the data by computer. Subsequent manual revision of the assemblies resulted in the incorporation of 19,661 fingerprinted BACs into 169 ordered sets of overlapping clones ('contigs'), each containing at least 3 clones. These contigs are ideal for parallel selection of BACs for large-scale sequencing and have supported the generation of more than 5.8 Mb of finished genome sequence submitted to GenBank; analysis of the sequence has confirmed the integrity of contigs constructed using this fingerprint data. Placement of contigs onto chromosomes can now be performed, and is being pursued by groups involved in both sequencing and positional cloning studies. To our knowledge, these data provide the first example of whole-genome random BAC fingerprint analysis of a eucaryote, and have provided a model essential to efforts aimed at generating similar databases of fingerprint contigs to support sequencing of other complex genomes, including that of human.