Gene-sized DNA molecules of the macronuclei in three species of hypotrichs: Size distributions and absence of nicks

Abstract

Macronuclear DNA s from three related hypotrichous ciliated protozoans were compared by agarose gel electrophoresis. Each was shown to be composed of DNA duplexes that yielded a unique pattern of bands overlying a continuous distribution of DNA sizes ranging from approximately 400 bp to approximately 20,000 bp. By EM, the number average molecular sizes for double-stranded DNA were 2,200 bp for Oxytricha sp., 2,514 bp for Stylonychia pustulata and 18,836 bp for Euplotes aediculatus. Contrary to previous reports we present evidence that the macronuclear DNA s in each of these three organisms lack single-stranded interruptions.

Telomeric DNA-protein interactions of Oxytricha macronuclear DNA.

“…The somatic macronucleus of Oxytricha contains some 24x 106 gene-sized DNA molecules, which range in length from 400 to 20,000 bp (Swanton et al 1980b;Prescott 1983). The ends of the DNA molecules are characterized by the sequence: 5'-CCCCAAAACCCCAAAACCCC .....…”

“…The reconstitution mixture consisted of TE plus 20 mM EGTA, 1 ~g DNA (1.4 pmole ends) and 0-4 pmole of each telomere protein per 8-12 ~1 sample. The molar concentration of the DNA was calculated using 2.2 kbp as the number average molecular weight of Oxytricha nova macronuclear DNA (Swanton et al 1980b). Protein concentrations were estimated using the assay of Sedmak and Grossberg (1972), with BSA used as the standard.…”

Cloning and Sequence Analysis of the Micronuclear and Macronuclear Gene Encoding Rab Protein ofEuplotes octocarinatus

“…During development of the macronucleus, the micronuclear chromosomes become fragmented, and a considerable portion of the DNA is eliminated. 5) In addition, sequences that interrupt genes, called internal eliminated sequences (IESs), are excised. The segments of the micronuclear precursor gene separated by the IESs are called macronuclear-destined sequences (MDSs).…”

Molecular genetics of a ciliate

“…The number average size of macronuclear DNA molecules determined by electron microscopy is 2200 BP (13). The total sequence complexity of macronuclear DNA is equal to 5.7x 107 BP (6).…”