Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes 22q11.2 deletion syndrome ?
    ### Response:
    What causes 22q11.2 deletion syndrome? 22q11.2 deletion syndrome is caused by a missing piece (deletion) of part of chromosome 22 in each cell. The deletion occurs near the middle of the chromosome at a location designated q11.2. Most people with 22q11.2 deletion syndrome are missing a piece of the chromosome that contains about 30 to 40 genes, many of which have not been well characterized.
    