Approximately what fraction of men were reported to carry the MAOA Warrior gene linked to aggression?

• A. One third
• B. One half
• C. One quarter
• D. Two thirds

Answer: (A)

Frequencies of genetic variants, especially on the X chromosome, determine how many men carry a given allele. The MAOA gene has different versions that affect how much Monoamine Oxidase A enzyme is produced. The low-activity version has been popularly called the Warrior gene, but whether it leads to aggression depends on environmental factors as well. In many population studies, about one third of men carry the low-activity MAOA variant, so roughly a third are carriers. That makes one third the best fit among the given options, since it approximates typical prevalence without overstating its occurrence. The others would imply a much higher or lower rate than what is commonly reported.