RT Journal
A1 Khan, Asis
A1 Böhme, Ulrike
A1 Kelly, Krystyna A.
A1 Adlem, Ellen
A1 Brooks, Karen
A1 Simmonds, Mark
A1 Mungall, Karen
A1 Quail, Michael A.
A1 Arrowsmith, Claire
A1 Chillingworth, Tracey
A1 Churcher, Carol
A1 Harris, David
A1 Collins, Matthew
A1 Fosker, Nigel
A1 Fraser, Audrey
A1 Hance, Zahra
A1 Jagels, Kay
A1 Moule, Sharon
A1 Murphy, Lee
A1 O'Neil, Susan
A1 Rajandream, Marie-Adele
A1 Saunders, David
A1 Seeger, Kathy
A1 Whitehead, Sally
A1 Mayr, Thomas
A1 Xuan, Xuenan
A1 Watanabe, Junichi
A1 Suzuki, Yutaka
A1 Wakaguri, Hiroyuki
A1 Sugano, Sumio
A1 Sugimoto, Chihiro
A1 Paulsen, Ian
A1 Mackey, Aaron J.
A1 Roos, David S.
A1 Hall, Neil
A1 Berriman, Matthew
A1 Barrell, Bart
A1 Sibley, L. David
A1 Ajioka, James W.
T1 Common inheritance of chromosome Ia associated with clonal expansion of Toxoplasma gondii
JF Genome Research 
JO Genome Research 
YR 2006 
FD September 01 
VO 16 
IS 9 
SP 1119 
OP 1125 
DO 10.1101/gr.5318106 
UL http://genome.cshlp.org/content/16/9/1119.abstract 
AB 
Toxoplasma gondii is a globally distributed protozoan parasite that can infect virtually all warm-blooded animals and humans. Despite the existence of a sexual phase in the life cycle, T. gondii has an unusual population structure dominated by three clonal lineages that predominate in North America and Europe, (Types I, II, and III). These lineages were founded by common ancestors ~10,000 yr ago. The recent origin and widespread distribution of the clonal lineages is attributed to the circumvention of the sexual cycle by a new mode of transmission—asexual transmission between intermediate hosts. Asexual transmission appears to be multigenic and although the specific genes mediating this trait are unknown, it is predicted that all members of the clonal lineages should share the same alleles. Genetic mapping studies suggested that chromosome Ia was unusually monomorphic compared with the rest of the genome. To investigate this further, we sequenced chromosome Ia and chromosome Ib in the Type I strain, RH, and the Type II strain, ME49. Comparative genome analyses of the two chromosomal sequences revealed that the same copy of chromosome Ia was inherited in each lineage, whereas chromosome Ib maintained the same high frequency of between-strain polymorphism as the rest of the genome. Sampling of chromosome Ia sequence in seven additional representative strains from the three clonal lineages supports a monomorphic inheritance, which is unique within the genome. Taken together, our observations implicate a specific combination of alleles on chromosome Ia in the recent origin and widespread success of the clonal lineages of T. gondii.