Regulation Of Eve Transcription In Stripe 2

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Even-skipped

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Express in odd segment, result in 7 stripes

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Pair rule genes and segmentation

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Combination of spatially distributed gap gene transcription factors
Activation of pair-rule genes in seven transverse stripes along the antero-posterio segmentation

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Establishment of segmentation domains

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Segment polarity genes
- encode components of two cell-cell signaling pathway
(Hedgehog, Wingless)
-Activated/repressed by pair-rule genes
Each expressed in alternating narrow stripes
Function to define A and P within each segment mutants have mirroring of one half of each segment.

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Establishing segment identity

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Segment polarity genes

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Homeotic mutations

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Mutation affecting segment identity
UltrabithoraxL thorax and set of wings in
HOx genes

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Hox genes

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8 genes, all encode homeo-domain family trnascription factors
Found in 2 gene complexes
display colinearity ( the order of gene on the chromosome is exactly the same as the one on the body)

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Establishing segment identity

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hox or selector genes

expressed in specific segments, some overlap

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In Ultrabithorax

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Ubx is expressed in developing halters
Forced expression of ubx in wing converts it into a haltere

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Estalishement of segment identity:

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Homeotic (or selector ) genes

Because some Hox genes are expressed.
Estalishment of appendages (antennae, legs, wings, halteres, etc) by dustal-less (Dll)

Dll expresssion marks the earliest stage in appendage development
No appendages in abdominal segments - don't express all

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Distal-less (Dll) expression in abdomen is repressed by Ubx and And-A

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since Ubx & And-A are transcription factors- can mimic mitants by deleting/ mutaging specific enhancers in the all cis-acting regulatory element (upstream of promoter)

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Identified dinding sites for further negative regulation of all

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Segment polarity gene products Engrailed (en) and Sloppy-paired
Each affect one half of each segment ( En represses posterior expression in each segmant Slp represses anterior)

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Thus the deciison to form appendages in a abdominal segment

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etc

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Aterior -posterior patterning in Drosophila

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Meternal effect (bdc, Hunchback) ->Zygotic geness (GAP) -> Pair-rule (7 stripes) -> Segment polarity -> Hox turn on by GAP and pair-rules genes

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Organization and function of hox genes is

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conserved in vertebrates
In mammals, hox genes have been duplicated twice
Found in four factors
Express colinear

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As in flies, loss of HOX gees in vertebrate leads to change in

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identity in serially repeated structures (vertebrea

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Translational control of developmental timingin C.elegans by miRNAs

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cell division follow a stereotyped pattern lineages

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let-7 mutant

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C-elegans cells divided an extra times and die because of vulva rupture

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miRNAS

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endogenous genes. Encode short (~21-25 nt) RNAs derived from double-strnaded RNA precursors. Transcribed as longer RNA transcripts (pro-miRNAS)
Imperect base-paring
- > end result - less target protein made.

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siRNAs

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exogenous genes.

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Line41 is the target of

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Let-7