As discussed in class, a common method for introducing a transgene into the genome of a mouse is to inject it (as a linear piece of DNA) into the nucleus of a zygote where it integrates into one of the zygote's chromosomes, at a random position. You are studying a newly discovered gene called nosight. Mutations in this gene lead to blindness. You already know that nosight mRNA is transcribed in all cell types of the embryonic eye (neural retina, non-neural retina, iris, corena, lens, etc). You are interested in understanding how nosight expression is regulated, and so you decide to define its enhancer. You generate a reporter transgene, in which 5000 bp of DNA surrounding the nosight gene is fused upstream of the GFP ORF. You inject this SAME reporter in independent experiments into 10 different zygotes, and allow them to develop into 10 transgenic mice. You then observe GFP expression each mouse. (Assume that for each mouse, every cell contains the transgene). You get the following results: 3/10 independent experiments showed NO expression of your transgene. 6/10 experiments GFP was activated in neural retinal cells. 1/10 experiments, the GFP reporter was expressed very highly in all blood cells, and in neural retinal cells. 5000 A. What parts, if any, of your gene's enhancer can you conclude are contained within your bp fragment in the transgene?
B. Do you expect that this gene has additional enhancers?
C. Propose a molecular explanation for each of these three different results.