. For example, women with a 45, X karyotype (Turner's syndrome [TS]) typically are not mentally retarded and have normal verbal abilities; however, some researchers believe they have visual-spatial impairments (Murphy & et.al., 1993, p. 1197).
TS occurs in about six percent per 10,000 female livebirths. Most affected subjects have non-mosaic 45, X karyotypes. The remainder are karyotypic variants, which include 45, X/46, XX and 45, X/47, XXX mosaicisms. Phenotypic features of TS karyotypes include short stature and streak gonads. During embryogenesis, ovarian development occurs, but oocytes are lost. Thus, TS children lack ovarian follicles and do not produce estrogen; most do not undergo spontaneous pubertal maturation and are infertile. Therefore, TS offers an opportunity to study the effects of sex steroids and of the X chromosome on the human brain. The neuroanatomical basis for the TS cognitive profile is unknown, but two of three published case-reports described right-sided cerebral abnormalities (Reske-Nielsen, E. & et.al., 1982, p. 181-190).
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