40. Aneuploid females with only one X chromosome is a characteristic of individuals with
(1) Cri du chat syndrome
(2) Klinefelter syndrome
(3) Down syndrome.
(4) Turner syndrome.

Concept

“Aneuploid females with only one X chromosome” means karyotype 45,X (monosomy X). This is the defining chromosomal pattern of Turner syndrome, in which a phenotypic female has complete or partial absence of one X chromosome.​

Option‑wise explanation

1. Cri du chat syndrome

   • Caused by a deletion of the short arm of chromosome 5 (5p−), an autosomal structural abnormality, not loss of an entire X chromosome.​

2. Klinefelter syndrome

   • Occurs in males, typically 47,XXY (extra X with Y), not females with a single X.​

3. Down syndrome

   • An autosomal trisomy (trisomy 21); sex chromosomes are usually normal (46,XX or 46,XY).​

4. Turner syndrome – correct

   • Classic karyotype 45,X, i.e., an aneuploid female with only one X chromosome; other variants are partial or mosaic monosomy X.​

Therefore, aneuploid females with only one X chromosome are characteristic of Turner syndrome (option 4).