Class 14 - Non-Mendelian Inheritance...

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Unformatted text preview: Non-Mendelian Inheritance Mitochondrial/cytoplasmic inheritance Nondisjunction Non-mendelian inheritance of leaf color in ‘ 4-o ’ clocks ’ ‘Maternal inheritance’, Independent of nuclear genes So far, we have talked about only NUCLEAR genes, but there is also…. Fig. 7.16 Cytoplasmic inheritance nucleus 0 0 0 0 0 0 0 0 Mitochondria and chloroplasts have circular DNA Mitochondria (mt): sites of ATP synthesis mtDNA; genes for special translation proteins genes for ATP biosynthesis proteins Mitochondria • Probably derived as an endosymbiant – May have come from an anerobic eukaryote that engulfed a “bug” – Bug can generate ATP using oxygen – Sequences of mitochondrial DNA are more closely related to eubacteria than to eukaryotes Mitochondrial features • Genome 15-16kb in size • 5-10 copies per organelle • 1000 per cell • Encodes 2 rRNAs, 22tRNAs, 13 proteins in humans • no introns • Found ONLY in the cytoplasm • NO WAY TO SEGREGATE!!! Mitochondrial Inheritance • Sperm have NO cytoplasm to speak of • All mitochondria come from mother • During cell division mitochondria are split randomly to daughters • If mutant, mutations are usually mixed - called HETEROPLASMY mutation No mutation Organelles are inherited Uniparentally (from one parent only) e.g. mt from mothers in human chloroplast from females in tobacco plants also called ‘ maternal inheritance’ Biparentally (from both parents) e.g. mt from both mating types in yeast chloroplasts in geraniums • In humans; maternal inheritance Haploid sperm + haploid egg -> zygote Zygote cytoplasm is almost entirely donated by egg All of mitochondria are from mother Human: phenotypes of mutant mt genes There are others What inheritance for a mt-based disease might...
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This note was uploaded on 02/25/2010 for the course MCDB 2150 taught by Professor Winey,mark during the Spring '06 term at Colorado.

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Class 14 - Non-Mendelian Inheritance...

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