Clonal analysis of nuclear differentiation in Tetrahymena

Mating type differentiation in tetrahymena thermophila: Characterization of the delayed refeeding effect and its implications concerning intranuclear coordination

“…We conclude that the two macronuclei of an exconjugant are statistically independent of one another in their response to starvation. 6) mt I1 shows a curious behavior, already noticed by Bleyman and Simon [15] and in less extreme form by Nanney and Allen [ 111 : when mt I1 appeared at all in one of our caryonides (eight independent occurrences), the macronucleus was pure for this mt ( Table 3, group D). Indeed, mt I1 caryonides account for six of the 13 pure caryonides observed under late refeeding.…”

“…Our present studies focus attention on another mt I1 anomaly already noted before, namely, the unusual tendency of newly developed mt 11-containing macronuclei to be pure or nearly pure for mt 11 [11,15]. A total of 37 mt 11-containing caryonides have now been analyzed.…”

“…Mixed caryonides heavily biased toward mating 11 could result from the loss of all the mt I1 mtd copies in an early segregant prior to the completion of differential replication. (The one exceptional mixed mt I1 caryonide could be explained either by a rare secondary recombinatiodgene conversion event in the macronucleus, yielding a recombinant ARF that combines the "differential replication" DNA sequence with an mtd locus differentiated to a non-11 mt or by a rare caryonide cell that inherited two new macronuclei [15]). These considerations lead us once more to raise the possibility that the mt I1 determinant is not a member of the m t -2 cluster of mt determinants [8].…”

“…A total of 37 mt 11-containing caryonides have now been analyzed. Bleyman and Simon [15], working with early refed mat-I homozygotes, and ourselves, working with early or late refed mat-2 homozygotes, found that all mt 11-containing caryonides (16 in total) were pure. Nanney and Allen [ll], working with early refed mat-1 and mat-2 homo-and heterozygotes, found 13 pure and eight mixed mt 11-containing caryonides.…”

Variability in the timing and outcome of macronuclear assortment inTetrahymena thermophila

“…An equal mixture of 35:10 and 22:23 nuclei gives an expected initial estimate of 33:12, moderating gradually to 29:16 after about 100 fissions. In view of the variation within pairs already known from the assortment of H serotypes (Bleyman, Simon & Brosi, 1966), this seems a reasonable explanation. It is also clear that small trends, even if very general in occurrence, cannot be taken as proof of the 66 subunit model.…”