(10 points) Dr. John Q. Scientist is a researcher who investigates the functions of a transmembrane protein found only in human liver cells. This transmembrane protein was named HLOR-1 (human liver orphan receptor-L, i.e., a receptor-like molecule for which a biological ligand has not yet been identified). HLOR-1 was cloned by way of "reverse genetics" based on a genetic disorder (phenotype observed in adulthood) that associates a genetic marker allele at 100% frequency. Further, upon complete cDNA cloning, with a sequence analysis, and computer modeling work, it is believed that the predicted structure of HLOR-1 resembles that of a growth factor receptor; hence the name HLOR-1. With the HLOR-1 cDNA in hand, John wishes to determine if mutations in the HLOR-1 gene are causative to the human genetic disorder, with the help of his talented and dedicated research team:
1): (5 points) Graduate student Bob was assigned the task of expressing a variant HLOR-1 protein in a human liver cell line. Bob generated five independent sub-lines of the cells, each with a chromosome integration of the HLOR-1 variant cDNA driven by a proper promoter and over-expressing the corresponding protein. Four of Bob's sub-lines produced a phenotype consistent in cell physiology with the manifestations of the genetic disorder, but one of his sub-lines did not produce this phenotype despite the expression of the variant HLOR-1 protein. Would Bob and John be able to conclude that the HLOR-1 variant is the cause of the genetic disorder? Why or why not?
2). (5 points) Post-doctoral fellow Jane was assigned the task of generating transgenic mice that over-express the variant HLOR-1 protein in adult mouse liver. Given Bob's results, could Jane get away with generating just one sub-strain/line of the transgenic mice over-expressing the variant HLOR-1 in the liver and presenting the disease phenotype, yet still help John make a strong argument about the variant HLOR-1 expression being the cause of the disorder? Why or why not?
