Cambridge Reference Sequence
The Cambridge Reference Sequence (CRS) for human mitochondrial DNA was first published in 1981[1] leading to the initiation of the human genome project.
A group under Dr. Fred Sanger at Cambridge University sequenced the mitochondrial genome of one individual of European descent during the 1970s, determining it to have a length of 16,569 base pairs (0.0006% of the nuclear human genome) containing some 37 genes.
When other researchers repeated the sequencing, some striking discrepancies were noted. The original published sequence included eleven errors, including one extra base pair in position 3107, and incorrect assignments of single base pairs. Some of these were the result of contamination with bovine and HeLa specimens. The corrected revised CRS was published by Andrews et al. in 1999.[2] (The original nucleotide numbering was retained to avoid confusion.) The reference sequence belongs to European haplogroup H2a2a. The revised CRS is designated as rCRS.
When mitochondrial DNA sequencing is used for genealogical purposes, the results are often reported as differences from the revised CRS. The CRS is a reference sequence rather than a record of the earliest human mtDNA. A difference between a tested sample and the CRS may have arisen in the lineage of the CRS or in the lineage of the tested sample.
An alternative Yoruba reference sequence has also been used sometimes instead of the Cambridge. It has a different numbering system with a length of 16,571 base pairs and represents the mitochondrial genome of one African individual.
As of 2012, the revised Cambridge Reference Sequence (rCRS), and the Yoruba reference sequence (Yoruba), are in the process of being replaced by the new Reconstructed Sapiens Reference Sequence (RSRS). The RSRS keeps the same numbering system as the CRS, but represents the ancestral genome of Mitochondrial Eve, which all currently known human mitochondria descend from. That is far more useful for comparing the changes in different haplogroups.
References
- ↑ Anderson S, Bankier AT, Barrell BG, de Bruijn MH, Coulson AR, Drouin J, Eperon IC, Nierlich DP, Roe BA, Sanger F, Schreier PH, Smith AJ, Staden R, Young IG (1981). "Sequence and organization of the human mitochondrial genome". Nature 290 (5806): 457–465. doi:10.1038/290457a0. PMID 7219534.
- ↑ Andrews RM, Kubacka I, Chinnery PF, Lightowlers RN, Turnbull DM, Howell N (1999). "Reanalysis and revision of the Cambridge reference sequence for human mitochondrial DNA". Nat Genet 23 (2): 147. doi:10.1038/13779. PMID 10508508.