Human Genetics Problem Set

Problem 11 Tutorial: Diagnosis of Klinefelter's syndrome

Klinefelter's syndrome (XXY) is an example of chromosomal aneuploidy that can be readily diagnosed by:

C. Karyotyping

Chromosomal aneuploid

Chromosomal aneuploid is a genetic condition in which an individual has either an abnormal number of one or more chromosomes, or has pieces of chromosomes lacking or in excess.

Klinefelter's syndrome

Klinefelter's syndrome, XXY males, can occur due to nondisjunction of X chromosomes during prophase of meiosis I in females.

One of the eggs from such a meiosis could receive both X chromosomes, and the other would receive no X chromosomes.

If these eggs are subsequently fertilized with normal sperm, various sex chromosome aneuploidies could occur:

XXY - sterile male who may have some female body characteristics, and in some cases increased learning hurdles.
(For more information visit the National Institute of Health's site on Understanding Klinefelter Syndrome, A Guide for XXY Males and their Families at http://www.nih.gov/health/chip/nichd/klinefelter/)

XXX - There are no real stigmata connected with this syndrome. Women with triple X usually are fertile.

XO - sterile female with short stature, with low mental ability, failure to undergo puberty (Turner's syndrome).

YO - Non-viable; genes on X chromosome required for development and survival.

Nondisjunction during sperm production can also result in aneuploidy of sex chromosomes.

Karyotype of Klinefelter's syndrome

To detect chromosomal aneuploidies, the number, types, and appearance of chromosomes is determined by karyotyping, a pictorial display of chromosomes photographed through the microscope.

The Biology Project
University of Arizona
Revised: November 5, 1998
Contact the Development Team