Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

Turner's syndrome is characterised by the monosomy of XO type. It is characterized by a lack of ovaries and menstrual cycle. Affected women are sterile and lack secondary sexual characteristics, although the external genitalia are present. The syndrome is named after the US endocrinologist H. H. Turner (18921970), who first described it. Down's syndrome is a congential form of mental retardation due to a chromosome defect in which there are three copies of chromosome no. 21 instead of the usual two. The affected individual has a short broad face and slanted eyes (as in the Mongolian races), short fingers, and weak muscles. Down's syndrome can be detected before birth by amniocentesis. It is named after the British physician John Down (182896), who first studied the incidence of the disorder. Klinefelter's syndrome is characterised by trisomy $(\mathrm{XXY})$. These are male individuals, who are phenotypically fairly normal but have a fairly low sperm count and therefore sterile.