Site hosted by Angelfire.com: Build your free website today!


This page is devoted to explaining the different types of Nondisjunction disorders that occur in our world. Nondisjunction disorders are when cell division development of the zygote has an imbalanced amount of genetic information. This imbalance affects the distribution of the chromosomes or genetic information that each cell has. Having abnormal amounts of karyotypes in the chromosomes will overload the cells and this in turn can kill the zygote or in some cases, a person with Nondisjunction disorder is born.



Nondisjunction is the failure of chromosomes to equally separate during meiosis. Meiosis is the steps or process' taken to duplicate genetic information and form two new cells. When this occurs it is called nondisjunction forming cells with either too many or not enough genetic information.


There are various karyotypes in our chromosomes that make our genetic "makeup". Abnormal amounts of specific karyotypes will affect different things in the body. Below are some of the disorders caused by Nondisjunction.



View Karyotypes of both men and women


Down Syndrome
The result of an extra copy of chromosome 21. Down syndrome affects 1:700 children and alters the child's phenotype either moderately or severely. These people can have heart defects, short stature, susceptibility to respiratory disease, shorter then average lifespan, can develop Alzheimer's and leukaemia easier. This syndrome can be correlated with the age of the mother but can be the result of Nondisjunction of the father's chromosome 21.

Patau Syndrome
The result of an extra copy of chromosome 13. These people have serious eye, brain, circulatory defects as well as cleft palate. This can effect 1:5000 live births and children rarely live more than a few months.

Edward's Syndrome
The result of an extra copy of chromosome 18. The child has almost every organ system affected. This effects about 1:10 000 live births. Children with this disorder do not live more than a few months.

Nondisjunction Of The Sex Chromosomes
These disorders can be fatal, but many people have these karyotypes and are fine.

Klinefelter Syndrome
There are two things that can happen :

1. The result of two X karyotypes and one Y karyotype.
This effects the males sex organs becoming sterile and develops more feminine body characteristics than male.

2. The result of one X karyotype and two Y karyotypes.
This people with this disorder are somewhat taller than average and often have below normal intelligence.

Trisomy X
The result in three X karyotypes and no Y karyotypes in women. This can effect 1:1000 live births they are healthy and fertile but usually cannot be distinguished from normal female.

Monosomy X (Turner's syndrome)
The result of only a single X karyotype in women. This effecs 1:5000 live births women with Turner's have only forty-five chromosomes (normal is forty-six) These people are genetically female but they do not mature sexually during puberty and are sterile. Ninety-eight percent of these fetuses die before birth.


There are many sites dedicated to this topic and have much more information then could ever be posted here. These are the sites I referenced during the production of this page.

Abnormal Meiosis

Human Gentics

Nondisjunction Lecture

Nondisjunction covered by a science class