β-Carotene is the precursor of vitamin A1.
Oxidation at C-15 converts retinol to the aldehyde, retinal, and further oxidation produces retinoic acid, a hormone that regulates gene expression. 

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β-Carotene is the precursor of vitamin A1.
Oxidation at C-15 converts retinol to the aldehyde, retinal, and further oxidation produces retinoic acid, a hormone that regulates gene expression. 

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Wnt signal transduction pathways classify into:

1. Canonical wnt pathway (β-catenin dependent)

2. Noncanonical wnt pathways (β-catenin independent)

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Noncanonical pathways can be divided into two types: 

1. The “planar cell polarity” pathway

2. The “Wnt/calcium” pathway

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Central player in the canonical Wnt pathway is β-catenin

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Homologs

β-catenin in vertebrates = Armadillo in Drosophila

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“canonical” Wnt signaling uses a second TM protein, LRP that associates with Frizzled in a Wnt signal– dependent manner.

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Homologs

LRP in vertebrates = Arrow in Drosophila