SOLVED PROBLEM 1. You want to study the development of the olfactory (smell-reception) system in the mouse. You know that the cells that sense specific chemical odors (odorants) are located in the lining of the nasal passages of the mouse. Describe some approaches for using reverse genetics to study olfaction.
There are many approaches that can be imagined. For reverse genetics, you would want to identify candidate genes that are expressed in the lining of the nasal passages. Given the techniques of functional genomics, this identification could be accomplished by purifying RNA from isolated nasal-passage-lining cells and using this RNA as a probe of DNA chips containing sequences that correspond to all known mRNAs in the mouse. For example, you may choose to first examine mRNAs that are expressed in the nasal-passage lining but nowhere else in the mouse as important candidates for a specific role in olfaction. (Many of the important molecules may also have other jobs elsewhere in the body, but you have to start somewhere.) Alternatively, you may choose to start with those genes whose protein products are candidate proteins for binding the odorants themselves. Regardless of your choice, the next step would be to engineer a targeted knockout of the gene that encodes each mRNA or protein of interest or to use RNA interference to attempt to phenocopy the loss-of-function phenotype of each of the candidate genes.