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Lecture 11

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Biology 1002B
Tom Haffie

Lecture 11: Intro to Prokaryotic Gene Structure  Devolution of eukaryotes: endomembrane and endosymbiosis  Modern Chlamydomonas cell have three different genomes… o Nuclear, mitochondrial and chloroplast genomes  Modern endoymbiont genomes are greatly diminished… o Nucleus: 120 000 kb, biggest o Mitochondrion: 16 kb, smallest o Chloroplast: 200 kb, second biggest  Mitochondrial and chloroplast are circular genomes, lots of copies of each  E. coli has about 5000 genes in about 5000 kb of circular DNA o On average 1 gene is about 333 amino acids  Vaucheria (algae) has only 169 genes in only 115 kb of circular cpDNA (chloroplast)  Humans have only 37 genes in only 16kb of circular mtDNA (mitochondria) o Only about a dozen proteins o Why the genome have 37 genes only a dozen proteins  Why are there disconnect from number of genes to number of proteins? o Maybe they’re not protein coding genes  Dead gene, not expressed  What do they code for?  tRNA, rRNA, RNA  All RNA are made by transcription of genes  Modern endosymbiont genomes are greatly diminished… o Why? From 5000 to 37 genes, why would cell want it’s mtDNA to nucleus  What kind of genes that can be lost  Genes that the organism that they do not need anymore o Exokinase, glycolysis genes, flagellum, don’t need get rid o Organelles that have less genes are easier to be replicated, so that less genes it has the it is better for them to have. o Transfer genes to the nucleus  Why to the nucleus?  Nucleus have more control, coordinated control  They have reactive oxygen species during ETC, in the organelles, ROS is very mutagenic, so that it makes sense to get rid of the genes to put it in a safe place  What can DNA in nucleus that organelles can’t do? o It can be transcribed o Organelles have their own transcription and translation systems, ribosomes in mitochondria and chloroplast o N
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