When nondisjunction occurs in a human ovary, the same chromosomal imbalance occurs. XO and XX/ individuals are seen in the human race. XO individuals are poorly developed females displaying a series of phenotypic traits known as Turner's syndrome. The XX/ individuals (XXY) are poorly developed males displaying a series of phenotypic traits known as Kleinfelter's syndrome. Whether a Turner's XO or a Kleinfelter's XXY, these individuals show poor sexual development and other phenotypic traits. From this, can you come up with a mechanism for sex determination in humans? Think about it, transcribe your comments and then scroll for your answer.
YOUR COMMENT:
In humans, sex is determined by a balance of metabolic forces that include, as in Drosophila the X to autosome ratio in addition to maleizing influences contained on the Y chromosome. Thus an XX/ individual has the normal X/ chromosome balance for males but in addition, the XX balance for females. Hence the failure to develop fully along a specific sexual line. The XO individual has the X to autosome ratio of males but lacking a functional Y chromosome, normal male development is impossible. For problems with nondisjunction among autosomes, flip to the next card.
