What Is the MAOA Gene?

The MAOA gene (Monoamine Oxidase A) encodes an enzyme that breaks down neurotransmitters—dopamine, norepinephrine, serotonin, and others—in the brain. 🧠

These neurotransmitters influence mood and behavior.

The MAOA gene is located on the X chromosome. Because of this, men (XY) have one allele and women (XX) have two alleles of MAOA[1][2].

The gene contains a promoter region with something called a variable number tandem repeat (VNTR).

This section can repeat a different number of times: common repeats are 2 (2R), 3 (3R), 3.5 (3.5R), 4 (4R), or 5 (5R)[2]. The 2R, 3R, and 5R alleles are associated with lower enzyme activity (called "MAOA-L" for low-activity), while 3.5R and 4R are considered "normal," or high-activity[2].

What Is the "Double Allele" MAOA Gene?

Misconceptions About the MAOA Gene

Nuanced Reality

Sources