Braille reading is a demanding task that requires the identification of rapidly varying tactile patterns. During proficient reading, neighboring characters impact the fingertip at ∼100 ms intervals, and adjacent raised dots within a character at 50 ms intervals. Because the brain requires time to interpret afferent sensorineural activity, among other reasons, tactile stimuli separated by such short temporal intervals pose a challenge to perception.
View Article and Find Full Text PDFInt J Syst Evol Microbiol
November 2002
The phylogenetic relationships between ciliate species in the suborder Tetrahymenina, order Hymenostomata, was investigated by comparing their telomerase RNA (TER) sequences. This relatively small RNA is an integral part of telomerase, the ribonucleoprotein enzyme that catalyses the synthesis of telomeric DNA. Despite a relatively rapid rate of primary sequence divergence, conserved functional and structural elements within TERs facilitate the accurate alignment of truly homologous nucleotides.
View Article and Find Full Text PDFTelomeric DNA - the short, tandemly repeated sequences at the ends of chromosomes - is synthesized by telomerase, a ribonucleoprotein enzyme that copies a specific template sequence within its integral RNA moiety. The error-prone telomerase from the ciliate Paramecium tetraurelia stereotypically misincorporates TTP at telomerase RNA templating nucleotide C52, accounting for the 30% TTTGGG repeats randomly distributed in wild-type telomeres. Paramecium tetraurelia telomerase has been isolated from macronuclear extracts and characterized with respect to the extension of telomeric primers in vitro.
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