- the LCR was first identified and characterized in Globin genes
- in the human visual system, an LCR has an important role in choosing either red or green opsin in a mutually exclusive manner
- each cone expresses only one pigment
- an LCR stochastically chooses one of the 2 promoter sites of the red-green pigment locus
- the physical interaction b/c the promoter and LCR activates the transcription
- b/c the red and green pigment genes are located on the X chromosome next to each other, this mutually exclusive acivation alone ensures monoallelic expression, you get equal # of red and green cones b/c its random, randomly interact w/ the 2 promoters
- monoallelic because it is on the X chromosome (cells randomly inactivate X), this is why males are more likely to be colorblind
- there is positive and there is negative LCR regulation
- since these notes are on the Olfactory Receptor cell and the rule how one olfactory neuron has one receptor, I will talk about positive regulation in regard to Olfactory Receptor gene expression
- structures of the transgenic and endogenous MOR28 genes (make two mice and cross them together)
- the transgenic MOR28 (Tg B6/lacZ) has a C57BL/6 background and is tagged w/ tau-lacZ
- put reporter at the end of the gene, a way of looking at where the gene is espressed, adding a gene
- the endogenous MOR28 (129/GFP) has a 129/Sv background and is tagged w/ gap-GFP
- GFP was introduced into the 129/Sv background by the knock-in method
- this shows that there is monoallelic expression of the odorant receptor gene and axonal projection of olfactory sensory neurones
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