Turner syndrome encompassess several chromosomal abnormalities, of which monosomy X is the most common. It occurs in 1 out of every 2500 female births. Instead of the normal XX sex chromosomes for a female, only one X chrmosome is present and fully functional. This is called 45, X or 45,X0, although other genetic variants occur. In Turner syndrome, female sexual characteristics are present but generally underdeveloped.