Evolution of mitochondrial DNA in Paramecium caudatum.

Behavioral Mutants in PARAMECIUM CAUDATUM.

Mutants of Paramecium caudatum with abnormal swimming behavior or responses to cations were obtained by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Some of the mutants, like pawn in P. tetraurelia, cannot swim backward and are called CNR. Seven independently obtained CNR mutants belonged to three complementation groups, designated as cnrA, cnrB and cnrC. Some characteristics of doubl...

Age-associated change in macronuclear DNA content in Paramecium caudatum.

Macronuclear DNA content in Paramecium caudatum was found to be almost unchanged with a mean of about 400C during the earlier two-thirds of the life span in terms of the number of fissions and then it dropped rapidly to about one-fifth of the initial content. The age when rapid DNA decline occurred corresponded to that when the characteristics of senescence appeared. This decreasing pattern of ...

The structure of trichocysts in Paramecium caudatum.

The structure of undischarged and discharged trichocysts has been examined in Paramecium caudatum, and their light-microscopic appearance compared with their fine-structural organization. In living specimens undischarged trichocysts appear to be of a single type with a unimodal variation in length about a mean of 37 fim. When fixed for electron microscopy or compressed beneath a coverslip many ...

Micronuclear Rna Synthesis in Paramecium Caudatum

In a generation time of 8 hr in Paramecium caudatum, the bulk of DNA synthesis detected by thymidine-(3)H incorporation takes place in the latter part of the cell cycle. The micronuclear cycle includes a G(1) of 3 hr followed by an S period of 3-3(1/2) hr. G(2) and division occupies the remaining period of the cycle. Macronuclear RNA synthesis detected by 5'-uridine-(3)H incorporation is contin...

Studies in the Respiration of Paramecium Caudatum