Maloof_Lecture13_SecAB

Maloof_Lecture13_SecAB - BIS2C Lecture 13 Jan 27, 2010...

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Unformatted text preview: BIS2C Lecture 13 Jan 27, 2010 Eukaryotic life cycles ! alternation of generations ! haplontic ! diplontic Review: eukaryotic cells Mitochondria ! Endosymbiosis ! Origin Chloroplasts ! Endosymbiosis ! Origin ! secondary and tertiary events Sexual reproduction Is the formation of new individuals by the fusion of two haploid nuclei Sexual reproduction All eukaryotic sexual life cycles have at least 2 steps: ! meiosis to reduce diploid cells to halpoids ! fusion of haploid gametes to produce a diploid cell 3 Life cycle variations Alternation of generations ! expansion of haploid and diploid phase through mitosis Alternation of generations ! A diploid spore-forming organism gives rise to a haploid gamete-forming organism ! When haploid gametes fuse a diploid individual is formed. ! Both stages multicellular and undergo mitosis Ulva Isomorphic alternation of generations 3 Life cycle variations Alternation of generations ! expansion of haploid and diploid phase through mitosis Haplontic life cycle ! expansion of haploid phase ! The only diploid cell is the zygote generated through fertilization Haplontic life cycle In the haplontic life cycle , the organism is haploid and the zygote is the only diploid stage. Fungus ( Rhizopus oligosporus ) (Haploid organism) HAPLOID ( n ) Mature organism ( n ) DIPLOID (2 n ) Zygote (2 n ) Spores ( n ) Gametes Male (n) Female ( n ) 3 Life cycle variations Alternation of generations ! expansion of haploid and diploid phase through mitosis Haplontic life cycle ! expansion of haploid phase only ! The only diploid cell is the zygote generated through fertilization Diplontic life cycle ! expansion of diploid phase only ! the only haploid cells are the gametes HAPLOID ( n ) Gametes Male ( n ) Female ( n ) Diplontic life cycle In the diplontic life cycle , the organism is diploid and the gametes are the only haploid stage. Elephant ( Loxodonta africana ) (Diploid organism) DIPLOID (2 n ) Zygote (2 n ) Mature organism (2 n ) BIS2C Lecture 13 Jan 27, 2010 Eukaryotic life cycles ! alternation of generations ! haplontic ! diplontic Review: eukaryotic cells Mitochondria ! Endosymbiosis ! Origin Chloroplasts ! Endosymbiosis ! Origin ! secondary and tertiary events 12 A Plant Cell An Animal Cell Mitochondria and chloroplasts are derived from: A. Bacteria C. The same precursor B. Other eukaryotes D. Evolved de novo Endosymbioses Drove Eukaryotic Evolution Hints that chloroplasts and mitochondria once were bacteria ! Surrounding by 2 or more cell membranes " Inner one looks like bacterial membranes ! Morphologically resemble bacteria ! Many contain their own genomes and encode some proteins and RNAs ! Many components resemble those of bacteria Endosymbiosis- Lynn Margulis Initial Evidence: Morphological (size, structure) Biochemical Contain DNA more similar in structure to DNA in bacteria (size, circular in shape) 16 Mitochondria 16 4.13 A Mitochondrion Converts Energy from Fuel Molecules into ATP Mitochondria and bacteria have similar ribosomal gene order Bacteria Mito- chondria N...
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Maloof_Lecture13_SecAB - BIS2C Lecture 13 Jan 27, 2010...

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