MATING TYPES IN THE CILIATE DILEPTUS ANSER. GENETICAL INSTABILITY IN THE
MATING TYPE SYSTEM
Z. I. Uspenskaya, A. L. Yudin
Institute of Cytology RAS, St. Petersburg;
e-mail: yudin@cit.ras.spb.ru
In FI and p2 from a cross between two clones of Dileptus anser isolated from natural sources (MT I x
MT III; MT = mating type), along with "normal" clones, many clones were observed demonstrating abnormal phenotype
with respect to the MT-character. Irregular features of the latter were as follows: a) a delay in maturation; b)
temporary reversion to immature or adolescent state, which means instability of maturity state; c) expression of
MT I and MT III, rather than MT II as in properly matured clones; d) changes in MT (i. e., MT instability); e)
appearance of totally unexpected MTs in terms of the scheme of genetic control of MTs in D. anser previously
suggested by Afon'kin and Yudin (1987) - e. g., of all three MTs in FI from the initial (analysing!) cross.
Amazingly, these abnormal D. anser clones closely resembled some selfer-clones of Tetrahymena
pigmentosa, previously reported as an example of genetic instability in the ciliate MT system (Simon, 1980;
Simon, Orias, 1987).
Key words: Dileptus anser, mating type, genetic instability
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