What is the diagnosis associated with a chromosome count of 45 XO?

A chromosome count of 45 XO is indicative of Turner syndrome. This genetic condition occurs when there is a complete or partial absence of one of the two X chromosomes typically found in females, leading to a total of 45 chromosomes instead of the usual 46. Turner syndrome is characterized by a variety of clinical features such as short stature, delayed puberty, ovarian insufficiency, and certain physical characteristics like a webbed neck and low-set ears.

The 45 XO karyotype specifically points to the absence of a second sex chromosome (the second X chromosome), which is a defining feature of Turner syndrome.

Other conditions mentioned in the options involve different chromosomal configurations. For instance, Down syndrome is associated with an extra chromosome 21 (trisomy 21), Klinefelter syndrome involves an additional X chromosome in males (47, XXY), and Androgen Insensitivity Syndrome occurs in individuals with a typical male karyotype (46 XY) who are resistant to male hormones. Hence, 45 XO specifically and directly correlates with Turner syndrome.