Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to 22q11.2 deletion syndrome ?
    ### Response:
    Most people with 22q11.2 deletion syndrome are missing a sequence of about 3 million DNA building blocks (base pairs) on one copy of chromosome 22 in each cell. This region contains 30 to 40 genes, many of which have not been well characterized. A small percentage of affected individuals have shorter deletions in the same region.
    