Answer:
The transgenic mouse must present fur without pigmentation, or with reduced pigmentation.
Explanation:
As seen in the question above, a group of scientists genetically engineers a mouse strain by deleting the mouse lyst gene and replacing it with the polar bear lyst gene. This will modify the genotype of the mice making them transgenic mice different from ordinary mice.
As you may already know, polar bears have pigment-free fur, for that reason, these animals have white fur, allowing them to camouflage themselves in the environment in which they live.
When the genes of these bears are not added to the genome of a mouse, we can expect the mouse fur to change, appearing without any type of pigmentation, becoming totally white, or, appearing lighter than normal.