GENE20001 Lecture Notes - Lecture 10: Transfer Rna, Electron Transport Chain, Intron
Have their own DNA genomes
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Multiple copies per organelle
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Encodes genes including some protein encoding genes
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Most proteins in organelles are nuclear encoded
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Origin of organelles explained by endo-symbiosis theory
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Major organelles - mitochondria and chloroplasts:
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Most but not all DNA in a cell is in the nucleus. This is inherited according to Mendel's laws
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DNA (encoding genes) is found within organelles in the cytoplasm (mitochondria and plastids
which include chloroplasts). These can be inherited but do not follow Mendel's laws
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Generate ATP by oxidative phosphorylation
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Fe-S biogenesis
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Various other metabolic processes
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Cellular signaling involved in apoptosis
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Cell cycle/growth
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Human mtDNA sequenced in 1981
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Most mitochondrial genomes are circular. Rarely linear
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Significant variation in size but very similar in gene content
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Mitochondria:
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In leaves. Fix C through photosynthesis. Other metabolic processes
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Plastids: non green chloroplasts
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Show to contain DNA in 1962
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First sequences determined in 1986 (tobacco and liverwort)
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Circular genomes
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Well conserved in land plants (similar size and genes)
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Chloroplasts:
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Organelle genomes similar in structure to bacterial genomes
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Fluorescent dye that stains nuclear DNA and DNA (nucleoids) within Euglena mitochondria.
The bright dots are the mitochondria
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Nucleoids: look like little black dots. Structures within organelles. Not membrane bound. Just a
cluster of DNA. Sensitive to DNase treatment. Mt/Cp have their own genome contained within
nucleoids
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10 Extra-chromosomal genomes (organelles,
endosymbiosis)
Tuesday, March 18, 2014
10:10 PM
Genetics Page 1
Document Summary
Most but not all dna in a cell is in the nucleus. Dna (encoding genes) is found within organelles in the cytoplasm (mitochondria and plastids which include chloroplasts). These can be inherited but do not follow mendel"s laws. Significant variation in size but very similar in gene content. First sequences determined in 1986 (tobacco and liverwort) Well conserved in land plants (similar size and genes) Organelle genomes similar in structure to bacterial genomes. Fluorescent dye that stains nuclear dna and dna (nucleoids) within euglena mitochondria. Mt/cp have their own genome contained within nucleoids. There are multiple copies of chromosomes per nucleoid. Land plant chloroplast genomes contain about 100 similar genes which code for: Other protein-coding genes mostly for photosynthesis and electron transport. Many cp genes arranged in bacterial operon-like clusters. Nuclear genome may code for precursor proteins which are transferred to organelle, processed and incorporated. Less compact due to intergenic spacers and introns.
