The complete, ungapped sequence of the short arms of human acrocentric chromosomes (SAACs) is still unknown almost 20 years after the near completion of the Human Genome Project. Yet these short arms of Chromosomes 13, 14, 15, 21, and 22 contain the ribosomal DNA (rDNA) genes, which are of paramount importance for human biology. The sequences of SAACs show an extensive variation in the copy number of the various repetitive elements, the full extent of which is currently unknown. In addition, the full spectrum of repeated sequences, their organization, and the low copy number functional elements are also unknown. The Telomere-to-Telomere (T2T) Project using mainly long-read sequence technology has recently completed the assembly of the genome from a hydatidiform mole, CHM13, and has thus established a baseline reference for further studies on the organization, variation, functional annotation, and impact in human disorders of all the previously unknown genomic segments, including the SAACs. The publication of the initial results of the T2T Project will update and improve the reference genome for a better understanding of the evolution and function of the human genome.

中文翻译：

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人类近端着丝粒染色体的短臂和人类基因组序列的完成


在人类基因组计划即将完成近 20 年后，人类近端着丝粒染色体 (SAAC) 短臂的完整、无间隙序列仍然未知。然而，13、14、15、21 和 22 号染色体的这些短臂含有核糖体 DNA (rDNA) 基因，这些基因对人类生物学至关重要。 SAAC 的序列显示各种重复元件的拷贝数存在广泛差异，其全部范围目前尚不清楚。此外，重复序列的全谱、它们的组织以及低拷贝数功能元件也是未知的。以长读长序列技术为主的端粒到端粒（T2T）项目近期完成了葡萄胎CHM13基因组的组装，为进一步研究组织、变异、功能注释奠定了基线参考，以及所有以前未知的基因组片段（包括 SAAC）对人类疾病的影响。 T2T项目初步结果的发布将更新和完善参考基因组，以更好地了解人类基因组的进化和功能。