分子診斷學(xué)概論(編輯修改稿)
2025-02-11 11:15 本頁面
【文章內(nèi)容簡介】 tion. Third, a more sophisticated view of chromatin structure has emerged, including its interrelationship with DNA replication and transcriptional regulation. Finally, integration of these new sources of information, in particular with respect to mammalian evolution based on inter and intraspecies sequence parisons, has yielded new mechanistic and evolutionary insights concerning the functional landscape of the human genome. Together, these studies are defining a path for pursuit of a more prehensive characterization of human genome function. ? The highlights of our findings to date include The human genome is pervasively transcribed, such that the majority of its bases are associated with at least one primary transcript and many transcripts link distal regions to established proteincoding loci. Many novel nonproteincoding transcripts have been identified, with many of these overlapping proteincoding loci and others located in regions of the genome previously thought to be transcriptionally silent. Numerous previously unrecognized transcription start sites have been identified, many of which show chromatin structure and sequencespecific proteinbinding properties similar to wellunderstood promoters. Regulatory sequences that surround transcription start sites are symmetrically distributed, with no bias towards upstream regions. Chromatin accessibility and histone modification patterns are highly predictive of both the presence and activity of transcription start sites. Distal DNaseI hypersensitive sites have characteristic histone modification patterns that reliably distinguish them from promoters。 some of these distal sites show marks consistent with insulator function. DNA replication timing is correlated with chromatin structure. A total of 5% of the bases in the genome can be confidently identified as being under evolutionary constraint in mammals。 for approximately 60% of these constrained bases, there is evidence of function on the basis of the results of the experimental assays performed to date. Although there is general overlap between genomic regions identified as functional by e x p
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