Pedigree Matters Deep-Rooted Anomalies in Female Families Mapping the Thoroughbred in the Equine Mitochondrial Tree

TB Mitochondrial DNA Mitochondria are the 'power plants' of the cell, the only organelles within it that are capable of independent reproduction. Inside each mitochondrion is a single, circular chromosome that is inherited only from the mother, therefore is effectively non-recombinant i.e., changes only by spontaneous mutation.  Such mutations that accumulate within a species over the course of many millennia result in diffentiation that defines matrilineally related groups large (clades aka: haplogroups),  smaller (sub-haplogroups), and smallest (haplotypes), as well as potential functional variation between groups, making mtDNA typing a useful tool for studying various aspects of the Thoroughbred horse.  In terms of quantity of the mitogenome sequenced, sample number, and pedigree information, no purpose of such study has greater need than that of assessing the accuracy of the stud book matrilineal record. Due primarily to the expense involved in mtDNA typing, no single source available at present completely fulfills that need. So the family/mtDNA type cross-reference below integrates information from many sources, though we especially wish to express our gratitude for that provided by Performance Genetics. It was inevitable that mtDNA typing would prove that some errors have crept into matrilineal records spanning more than three centuries during which the Thoroughbred spread far and wide from its country of origin.  More remarkable, and an enduring testament to the earliest compilers of the General Stud Book, is the extent to which so many of the Lowe-numbered families have clearly conserved the same mtDNA type since the foundation era.

English & Half-Bred Families

American Families

Colonial Famlies

Families/branches sampled	Expected mtDNA Haplotype * type not yet fully defined	Remarks MRCA = Most Recent Common [matrilineal] Ancestor by stud book record of samples typed .
A1	G2	MRCA - Ballet (USA 1871)
A2	I*	Single sample
A4	N1a	MRCA - Planutess (USA 1908)
A5	N2	MRCA - Thora (USA 1878)
A10	N1 or N1a	MRCA - Madam Bosley (USA 1829c)
A11	I*	Single sample
A13	N1 or N1a	MRCA - Darlin Lindy (USA 1986)
A14	E,G, or H	MRCA - Row Stitch (USA 1964)
A16	A*	Single Sample
A21	M2	Single Sample
A24	I*	MRCA - Lady's Answer (CAN 1976)
A29	L1a	MRCA - Self Control (USA 1955)
a48	A1a	Undetermined. Pedigree available for only one of the samples.

Published sources consulted additional to the relevant stud books: Achilli A, Olivieri A, Soares P, Lancioni H, Kashani BH, Perego UA, Nergadze SG, Carossa V, Santagostino M, Capomaccio S, Felicetti M, Al-Achkar W, Penedo M C, Verini-Supplize A, Houshmand M, Woodward S R, Semino, O, Silvestrelli M, Giuliotto E, Pereira L, Bandelt H J, Torroni A: Mitochondrial genomes from modern horses reveal the major haplogroups that underwent domestication. PNAS USA. 2012 Feb 14;109(7):2449-54 Bobinski, Capt. K, and Count S. Zamoyski. Family Tables of Racehorses. London. J A Allen. 1953. Bower M A, Campana M G, Nisbet R E R, Weller R, Whitten M, Edwards C J, Stock F, Barrett E, O’Connell T C, Hill E W, Wilson A M, Howe C J, Barker G, Binns M. Truth in the bones: Resolving the identity of the founding elite thoroughbred racehorses. Archaeometry. 2012[A]. doi:10.1111/j.1475-2012.00666.x Bower M A, Whitten M, Nisbet R E R, Spencer M, Dominy K M, Murphy A M, Cassidy R, Barrett E, Hill E W, Binns M. Thoroughbred racehorse mitochondrial DNA demonstrates closer than expected links between maternal genetic history and pedigree records. J Anim Breed. Genet. 2012[B]. doi:10.1111/j.1439.0388.2012.01018. Harrison, F. Early American Turf Stock 1730-1830 (two vols.). Richmond. Old Dominion Press. 1934. Hill E W, Bradley D G, Al-Barody M, Ertugrul O, Splan R K, Zakharov I, Cunningham E P. History and integrity of thoroughbred dam lines revealed in equine mtDNA variation. Anim Genet. 2002 Aug;33(4):287-94. Lowe, C B, (W. Allison, ed.). Breeding Racehorses by the Figure System. The Field and Queen (Horace Cox) Ltd., UK. Peng MS, Fan L, Shi NN, Ning T, Yao Y-G, Murphy RW, Wang WZ, Zhang YP. DomeTree: a Canonical Toolkit for Mitochondrial DNA Analyses in Domesticated Animals. Mol Ecol Resour. (2015)DOI: 10.1111/1755-0998.12386 Rogers, B. Finding Tregonwell’s Natural Barb Mare. Bluebloods. Oct., 2014:30-35. Rogers, Byron. CEO Performance Genetics. Personal communications. 2017. © 2023 Judy Baugh