RESUMEN
Deletions of the AZFc (azoospermia factor c) region of the Y chromosome are the most common known cause of spermatogenic failure. We determined the complete nucleotide sequence of AZFc by identifying and distinguishing between near-identical amplicons (massive repeat units) using an iterative mapping-sequencing process. A complex of three palindromes, the largest spanning 3 Mb with 99.97% identity between its arms, encompasses the AZFc region. The palindromes are constructed from six distinct families of amplicons, with unit lengths of 115-678 kb, and may have resulted from tandem duplication and inversion during primate evolution. The palindromic complex contains 11 families of transcription units, all expressed in testis. Deletions of AZFc that cause infertility are remarkably uniform, spanning a 3.5-Mb segment and bounded by 229-kb direct repeats that probably served as substrates for homologous recombination.
Asunto(s)
Deleción Cromosómica , Infertilidad Masculina/genética , Cromosoma Y/genética , Secuencia de Bases , Inversión Cromosómica , Cromosomas Humanos Par 3/genética , Proteína 1 Delecionada en la Azoospermia , Evolución Molecular , Duplicación de Gen , Humanos , Masculino , Modelos Genéticos , Datos de Secuencia Molecular , Oligospermia/genética , Especificidad de Órganos , Mapeo Físico de Cromosoma , Proteínas de Unión al ARN/genética , Recombinación Genética/genética , Análisis de Secuencia de ADN , Eliminación de Secuencia/genética , Homología de Secuencia de Ácido Nucleico , Espermatozoides/metabolismo , Secuencias Repetidas en Tándem/genética , Testículo/metabolismo , Transcripción Genética/genéticaRESUMEN
The genome of the model plant Arabidopsis thaliana has been sequenced by an international collaboration, The Arabidopsis Genome Initiative. Here we report the complete sequence of chromosome 5. This chromosome is 26 megabases long; it is the second largest Arabidopsis chromosome and represents 21% of the sequenced regions of the genome. The sequence of chromosomes 2 and 4 have been reported previously and that of chromosomes 1 and 3, together with an analysis of the complete genome sequence, are reported in this issue. Analysis of the sequence of chromosome 5 yields further insights into centromere structure and the sequence determinants of heterochromatin condensation. The 5,874 genes encoded on chromosome 5 reveal several new functions in plants, and the patterns of gene organization provide insights into the mechanisms and extent of genome evolution in plants.