Monocistronic vs Polycistronic Genes

3. Arrows indicate mito. Ribosomes.Arrows indicate mito. Ribosomes.

5. Evolutionary questions about the Mitochondrial RNA Polymerase How and when was the phage RNAP gene acquired? What happened to the bacterial RNAP genes in the original endosymbiont?

6. Look at earlier eukaryotes In Pylaiella, a eukaryotic brown alga, a phage-like polymerase gene is in the mitochondrial genome. Suggests that the nuclear-encoded, phage-like mitochondrial RNAP came from the endosymbiont.

11. Chloroplast Bacterial-like RNAP composed of Core + Sigma factor Core = 4 subunits, a2 b b' a is encoded by the rpoA gene b is encoded by the rpoB gene (also sometimes split) b' is encoded by the rpoC1 and rpoC2 genes Sigma factor needed to initiate transcription at the promoter (recognizes -10, -35 promtoers) Nuclear encoded, family of ~6 genes in Arabidopsis Inhibited by rifampicin

12. Chloroplast Phage-like (NEP) polymerase Gene is similar to the 1-subunit phage (e.g., T7 phage) RNA polymerases Nuclear gene(s) Enzyme insensitive to rifampicin Promoter is a single region of 7-10 bp (different from -10,-35 promoters) Specificity factor not yet identified

15. Chloroplasts are only the main form of a class of Organelles: Plastids 1. Proplastids - precursor of all plastids, found in meristems 2. Etioplasts - form in shoots of dark-grown plants, distinctive internal structure 3. Chloroplasts - in all green tissues 4. Amyloplasts - prominent in roots, store starch, colorless 5. Chromoplasts - in mature fruit, lots of carotenoids, little chlorophyll