A more thorough explanation:

XYY syndrome is a genetic condition where a male has an extra Y chromosome. This means that instead of having the usual XY chromosomes, they have XYY chromosomes. This condition is rare and occurs in about 1 in every 1,000 male births.

Some people believe that XYY syndrome can cause increased aggressiveness and antisocial behavior, which may lead to criminal conduct. However, this theory has been largely discredited and there is no evidence to support it.

Examples of XYY syndrome are:

• A male baby is born with XYY chromosomes instead of the usual XY chromosomes.
• A man is diagnosed with XYY syndrome after experiencing fertility problems.

These examples illustrate the definition of XYY syndrome by showing that it is a genetic condition that affects males and is characterized by the presence of an extra Y chromosome. However, it is important to note that having XYY syndrome does not necessarily mean that a person will exhibit any specific behaviors or traits.