XYY theory

• The XYY Theory

  A genetic condition in which a male has an extra Y chromosome, giving a total of 47 chromosomes
• this condition of the XYY theory occurs in about 1 in 1000 male births
• XYY condition

  • The presence of an extra Y chromosome can cause criminal behavior
• Jacob (1965): 'Some XYY men have an increase in aggression compared to XY men, and have been labelled as "super males"'
• XYY syndrome


  • Serial killer John Wayne Gacy was suggested to have the XYY syndrome
• Some criminologists have suggested that Gacy was "born to kill"
• Sex chromosomes


  Females have XX, males have XY. The Y chromosome determines maleness.
• XYY theory involves an extra Y chromosome, giving XYY