Elmer Pfefferkorn, Dartmouth University, established the basic
principles of genetic mapping in T. gondii. Drug resistance
markers were generated in two strains of T. gondii that were
adapted to use in the laboratory. Fortuitously, these strains
included the type II and III lineages: clone
was derived from the type II Me49
strain, originally isolated from a sheep in
California; and CEP, a type III strain solated from a cat in
Dartmouth, NH. Dr.
established here is no predetermined mating type, but rather a single
organism can complete the entire
(Pfefferkorn et al.
Consequently, when two strains infect a cat simultaneously, they can
undergo self-mating or outcross to generate recombinant progeny.
of inheritance and the
ratios of progeny obtained help confirm the haploid nature of the
and Pfefferkorn 1980).
Some of the advantages of
classical genetics in T. gondii include: a relatively stable
genome allows simple linkage analysis, a single cross can generate
thousands of distinct progeny, haploidy simplifies genetic typing, and
allows direct observation of phenotypes, progeny can be cryo-preserved
and analyzed at a later date. Two primary experimental crosses have
been used in the generation of
linkage maps for T. gondii.
II x III crosses
I x III cross