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20 Cards in this Set
- Front
- Back
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Lewis' model of Bithorax complex
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All genes active = all segments, none active = only T2 segment, each gene makes one extra segment identity.
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How correct was Lews's model of Bithorax complex?
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Broadly right, but not that simple.
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True model of Bithorax complex
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Transcripts roughly in area of segments they affect, but ovlap adjacent segments, segment identity specified by more complex combinatorial code
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Denell and Brown's work on HOX complex
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Large deletion that removes all but most anterior gene, lethal homozygous for this deficiency has all segments with antennae on them
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homeobox domain
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Each homeotic protein has a homeobox domain
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Where is the homeobox usually located on the protein?
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Near C-terminus
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How large is the homeobox domain?
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60 AA
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How conserved is the homeobox domain?
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Highly conserved, AA identity from 50-80%
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What is the motif of the homeobox?
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helix-turn-helix
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Homeotic protein use
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master controllers for transcriptional cascade of genes involved in making various segments
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HOX complex evolution within arthropoods
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Highly conserved order of genes (same as their pattern of expression in embryos head to tail), only broken up in Diptera as Antennapedia and Bithorax
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How did the HOX complex evolve?
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Tandem gene duplication: original gene duplicated in tandem somehow, 2 genes diverged, continued expansion of tandem array
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HOX complex evolution in Drosophila
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Some genes flipped over during tandem gene duplication, high level of genome flux
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HOX complex evolution in mammals
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4 HOX complexees from 2 rounds of tetraploidization in early vertebrates genomes
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What is the basal chordate, and how do we know?
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Amphioxis, has only one HOX complex instead of the later evolved 4
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ParaHox complex
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Combo of duplications of genes in complexes, duplication of complexes, and then loss of particular gene
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HOX regulation of downstream genes
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HOX regulatess many downstream genes that mediate formation of segment-specific structures
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How does the HOX complex produce halteres in Diptera?
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Suppression of Ultrabithorax in hindwing formation
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HOX suppression of Ubx protein using RNAi leads to what in Ocepelltis bugs?
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Membranous hind wing transformed into colorful forewing phenotype
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HOX complex relates to prenatal horns of beetles how?
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Sex-combs-reduced expressed in the horns, knock down using RNAi = no horns and defects in mouthparts
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