BIOB11H3 Lecture 5: Molecular Cell Biology Lecture 5.docx
15 Mar 2013
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Because of these properties, these rnas are referred to as heterogeneous nuclear. Rnas (hnrnas), and the red radioactivity line in figure 11. 17a indicates them. When cells that have been incubated in [ Label cells for short period of time with 32p. Purify rna, centrifuge to separate molecules by size. Determine od (rna) and radioactivity (labeled hnrna rna). Large molecules come out first followed by the smaller molecules. The red lines indicate radioactivity in each fraction, provide information about the number of radioactive nucleotides incorporated into different-sized rnas during the brief pulse. Evident that neither hnrna nor the mrna consititute significant fraction of the rna reason is that these. Rnas are degraded after relatively brief period of time. Half-life how long before degradation or destroyed on purpose. Half-life of hnrna/mrna:minutes to hours (average 40min) Half-life of rrnas: days/months; accumulation occurs: for rrna (pol i): initial 45s 28s, 18s, 5. 8s. Yes: pulse chase strategy used (fig 11-17)
