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Lecture 11

Lecture 11.docx

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Biology 1002B
Denis Maxwell

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Lecture 11: Intro to Prokaryotic Gene Structure 1. Relative sizes of typical mitochondrial, chloroplast and nuclear genomes  Mitochondrion: 16 kb  Chloroplast: 200 kb (circular)  Nucleus: 120 000 kb (the most)  About 1kb/gene ish o 1 Kb= 1000 nucleotides (3 nucleotides in codon) o 1000/3 = 300-400 amino acids in a particular protein 2. Why would there be more genes than proteins?  Many genes makes same protein for back up  Maybe not all are protein coding genes (e.g. code for rRNA. tRNA, mRNA) 3. Rubisco structure and assembly from components coded by different genomes  Large subunits of rubisco made by chloroplast  Small subunits made by nucleus and brought into chloroplast 4. Possible reasons why modern organelle genomes have become dramatically smaller over evolutionary time  Lost in mitochondria since nucleus is taking over  Doesn’t need that gene to function anymore o Redundant genes, glycolysis cytosolic genes such as hexokinase are in nucleus o Flagella (don’t need mitochondria swimming around) o Hosts in which their mitochondria has suffered a mutation has lost redundant genes  Genomes easier to replicate  Selective advanatage  Get rid of genes by dumping them or through lateral gene transfer 5. Possible reasons why genes have moved to the nucleus from organelles over evolutionary time  Why would it advantageous to have genes in nucleus and not in the mitochondria?  Edit RNA in nucleus  Create variation through sexual recombination  Mitochondria’s ETC produce ROS o Genes not safely stored  Get genes into nucleus for control 6. Possible reasons why certain genes have not moved to the nucleus from organelles  Need those genes locally in the organelles o Simpler o Local production o Local control  More convenient, readily available  Genes/proteins cannot be moved into the nucleus o Too big o Organelle prokaryotic genes may not work in nucleic eukaryotic gene  Gene
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