What type of chromosomal alteration does Turner syndrome involve?

Turner syndrome is characterized by the presence of a complete or partial absence of one of the two X chromosomes, which fits the definition of a missing chromosome. In individuals with Turner syndrome, the typical chromosomal arrangement of two sex chromosomes (XX in females) is altered to have only one X chromosome along with the absence of the second sex chromosome. This is often denoted as 45,X instead of the typical 46,XX configuration found in normal females.

The lack of a second X chromosome results in various physical and developmental features associated with the syndrome, such as short stature, delayed puberty, and certain medical issues. The recognition of Turner syndrome as involving a missing chromosome is crucial for understanding its genetic basis and the implications for the health and development of affected individuals.