Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) 47,XYY syndrome ?
    ### Response:
    47,XYY syndrome is characterized by an extra copy of the Y chromosome in each of a male's cells. Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most males with 47,XYY syndrome have normal sexual development and are able to father children.
    