Analysis of Paramecium Macronuclear DNA Using Pulsed Field Gel Electrophoresis

Publisher Website
Google Scholar
Abstract
.We have analyzed the macronuclear DNA of Paramecium tetraurelia using orthogonal‐field‐altemation gel electrophoresis. The mean size of the linear macronuclear DNA molecules is approximately 450 kb. Less than 6% of the macronuclear DNA is larger than 800 kb. Using pulse times of 20, 40, 60 and 90 s we show that the macronuclear fragment containing the A type variable surface antigen gene migrates reproducibly as a 320‐kb linear DNA. Over the same pulse times we describe the unusual migration of the ribosomal RNA gene (rDNA) of P. tetraurelia. At pulse times of 20 and 40 s the rDNA migrates at limit mobility (300 and 500 kb, respectively) whereas with 60‐ and 90‐s pulse times, 2 components of rDNA are observed; 1 fraction independent of pulse time migrating at limit mobility, and a 2nd component migrating between 100‐kb and 400‐kb linear markers. Based upon previous electron micrographic studies of Paramecium rDNA as well as data presented here we conclude that the majority of Paramecium rDNA molecules are a circular DNA form.