RESUMO
Human chromosome 2 is unique to the human lineage in being the product of a head-to-head fusion of two intermediate-sized ancestral chromosomes. Chromosome 4 has received attention primarily related to the search for the Huntington's disease gene, but also for genes associated with Wolf-Hirschhorn syndrome, polycystic kidney disease and a form of muscular dystrophy. Here we present approximately 237 million base pairs of sequence for chromosome 2, and 186 million base pairs for chromosome 4, representing more than 99.6% of their euchromatic sequences. Our initial analyses have identified 1,346 protein-coding genes and 1,239 pseudogenes on chromosome 2, and 796 protein-coding genes and 778 pseudogenes on chromosome 4. Extensive analyses confirm the underlying construction of the sequence, and expand our understanding of the structure and evolution of mammalian chromosomes, including gene deserts, segmental duplications and highly variant regions.
Assuntos
Cromossomos Humanos Par 2/genética , Cromossomos Humanos Par 4/genética , Animais , Composição de Bases , Sequência de Bases , Centrômero/genética , Sequência Conservada/genética , Ilhas de CpG/genética , Eucromatina/genética , Etiquetas de Sequências Expressas , Duplicação Gênica , Variação Genética/genética , Genômica , Humanos , Dados de Sequência Molecular , Mapeamento Físico do Cromossomo , Polimorfismo Genético/genética , Primatas/genética , Proteínas/genética , Pseudogenes/genética , RNA Mensageiro/análise , RNA Mensageiro/genética , RNA não Traduzido/análise , RNA não Traduzido/genética , Recombinação Genética/genética , Análise de Sequência de DNARESUMO
We report an improved draft nucleotide sequence of the 2.3-gigabase genome of maize, an important crop plant and model for biological research. Over 32,000 genes were predicted, of which 99.8% were placed on reference chromosomes. Nearly 85% of the genome is composed of hundreds of families of transposable elements, dispersed nonuniformly across the genome. These were responsible for the capture and amplification of numerous gene fragments and affect the composition, sizes, and positions of centromeres. We also report on the correlation of methylation-poor regions with Mu transposon insertions and recombination, and copy number variants with insertions and/or deletions, as well as how uneven gene losses between duplicated regions were involved in returning an ancient allotetraploid to a genetically diploid state. These analyses inform and set the stage for further investigations to improve our understanding of the domestication and agricultural improvements of maize.