If isolating a copy of a gene coding for a protein in the stomach, could that gene be located in cheek cells?

yes, all cells in our body contain the same genetic material.


If the person is genetically diseased(i.e inherited a genetic disease) then it may not be found in all of his body cells because that gene is propably replaced or mutated when he/she inherited it.

If isolating a copy of a gene coding for a protein in the stomach, could that gene be located in cheek cells?
Yes but it won't probably be expressed. In order to do this, it should be under the control of a cheek-cells promoter, rather than one of stomach cells. Genes are expressed according to the promoters they are controlled by, most of which are tissue-specific