Genetics Genotypes

"Mini Mouse has a red nose, and Mickey Mouse has a red nose too. They had several children and of their F1 half of the males had black noses, half the males had red noses, and all of the females had red noses! Mini was also married to another mouse called Timmy. Timmy had a black nose. Mini and Timmy had children and half of all their F1 had black noses, the other half had red noses. A red nose in a mouse is caused by the expression of the R gene. The R gene has one intron. In black nosed mice, the R intron is not removed since these mice are missing a SnRP. This particular SnRP is expressed in noses of red nosed mice. Explain these results by describing how and why introns are removed and Proved the genotypes of Mini, Mickey and Timmy, and their children. "