yang lengkap manusia genom sequence of the two X chromosomes and autosomes from the female tissue derived cell line has been completed. This includes the 8% of the genom sequence that was missing in the original draft that was released in 2001.
yang lengkap manusia genom sequence of the entire 3.055 billion base pairs has been revealed by the Telomere-to-Telomere (T2T) Consortium. This represents the largest improvement to the manusia rujukan genom released in 2001 by Celera Genomics and the International Manusia Genom Sequencing Consortium. That genom sequence covered most of the euchromatic regions while either leaving out the heterochromatin regions or erroneous representation. These regions comprise 8% of the manusia genom that has finally been revealed. The new T2T-CHM13 reference1 termasuk urutan lengkap untuk semua 22 autosom ditambah Kromosom X. Urutan rujukan baharu ini juga telah membetulkan banyak ralat, dan telah menambah kira-kira 200 juta bp jujukan novel yang mengandungi 2,226 salinan gen, yang mana 115 daripadanya diramalkan sebagai pengekodan protein.
The current GRCh38.p13 reference genome has been as a result of two major updates, one in 2013 and the other one on 2019 on the 2001 Celera genome sequence. However, it still had 151 million base pairs of unknown sequence distributed throughout the genom, including pericentromeric and sub telomeric regions, duplications, gene and ribosomal DNA (rDNA) arrays, all of which are necessary for fundamental cellular processes. The new reference has been named as T2T-CHM13 as it comes from sequencing the DNA from CHM13 (Complete Hydatiform Mole) cell line and is performed by T2T consortium. The cell line is derived from abnormal fertilized egg or an overgrowth of tissue from the placenta in which women appears to be pregnant (false pregnancy), hence the sequence represents only of the two X chromosomes and autosomes of the female. Multiple sequence technologies have been put to use such as PacBio, Oxford Nanopore, 100X and 70X Illumina sequencers to name a few. The technological advances in sequencing have led to the sequencing of the remaining 8% as mentioned above.
Satu-satunya had bagi urutan T2T-CHM13 ialah kekurangan kromosom Y. Penjujukan ini sedang dijalankan, menggunakan DNA daripada garisan sel HG002, yang mempunyai 46 (23 pasang) dengan karyotype XY. Urutan itu kemudiannya akan dipasang menggunakan kaedah yang sama yang dibangunkan untuk genom CHM13 homozigot.
Ketersediaan T2T-CHM13 sebagai rujukan baharu genom mewakili satu kejayaan besar yang akan membantu dalam memahami peranan kawasan heterokromatin dan membantu memahami kesannya terhadap proses selular dengan lebih terperinci. Sehingga penjujukan kromosom Y selesai, ini akan berfungsi sebagai genom rujukan untuk kajian masa depan dalam memahami proses dan fungsi selular.
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Rujukan
- Nurk S, Koren S, Rhie A, Rautiainen M, Bzikadze A V, Mikheenko A et al. The complete sequence of a manusia genome bioRxiv 2021.05.26.445798; DOI: https://doi.org/10.1101/2021.05.26.445798
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