Cambridge Reference Sequence
Encyclopedia
The Cambridge Reference Sequence (CRS) for human
mitochondrial DNA
was first published in 1981 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 total 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. (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 usually reported as differences from the revised CRS. Such differences are not necessarily mutations: the CRS is a reference sequence rather than a record of the earliest human mtDNA. A difference from the CRS may represent a nucleotide that was ancestral to the haplotype of the CRS, which would mean that the mutation occurred in the CRS reference specimen rather than the tested specimen, or may represent an actual mutation.
Human
Humans are the only living species in the Homo genus...
mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
was first published in 1981 leading to the initiation of the human genome project
Human Genome Project
The Human Genome Project is an international scientific research project with a primary goal of determining the sequence of chemical base pairs which make up DNA, and of identifying and mapping the approximately 20,000–25,000 genes of the human genome from both a physical and functional...
.
A group under Dr. Fred Sanger at Cambridge University
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
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 total 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
HeLa
A HeLa cell is a cell type in an immortal cell line used in scientific research. It is the oldest and most commonly used human cell line. The line was derived from cervical cancer cells taken on February 8, 1951 from Henrietta Lacks, a patient who eventually died of her cancer on October 4, 1951...
specimens. The corrected revised CRS was published by Andrews et al. in 1999. (The original nucleotide numbering was retained to avoid confusion.) The reference sequence belongs to European haplogroup H2a2a
Haplogroup H (mtDNA)
In human mitochondrial genetics, Haplogroup H is a human mitochondrial DNA haplogroup that likely originated in Southwest Asia 25,000-30,000 YBP.-Origin:...
. The revised CRS is designated as rCRS.
When mitochondrial DNA sequencing is used for genealogical purposes, the results are usually reported as differences from the revised CRS. Such differences are not necessarily mutations: the CRS is a reference sequence rather than a record of the earliest human mtDNA. A difference from the CRS may represent a nucleotide that was ancestral to the haplotype of the CRS, which would mean that the mutation occurred in the CRS reference specimen rather than the tested specimen, or may represent an actual mutation.