Answer;
-Skin cells have the crystallin gene but do not express it.
-Skin cells do not need crystallin for their function.
Step-by-step explanation;
Crystallin protein has a specific function in lens cells, and skin does not make lenses. It would be wasteful to make protein that is not needed, and the crystallin protein might even have a detrimental effect if it were expressed in skin cells. So even though skin cells have the gene to make crystallin, they do not express that gene.