Final answer:
The gene encoding β2 micro-globulin, part of MHC class I molecules, is located on chromosome 15 and is vital for the immune system's recognition process.
Step-by-step explanation:
The gene encoding the β2 micro-globulin (β2m), which is an invariant light chain (LC) of HLA class I molecules, is located on chromosome 15 in humans. This gene is part of the major histocompatibility complex (MHC), a collection of genes that code for glycoproteins expressed on the surface of all nucleated cells. The β2m does not vary between the different MHC class I molecules, paired up with three highly polymorphic proteins (HLA-A, HLA-B, and HLA-C), forming the complete MHC class I molecule crucial for the immune system's recognition process.