From ArticleWorld

Aneuploidy is a chromosomal state that involves the existence of an abnormal number of certain chromosomes or sets of chromosomes in the nucleus. In the case of humans, pairs of chromosomes (diploidies) are normal.

This leads to a number of chromosomal disorders appearing while the reproductive cells are forming or during the early fetal life. Aneuploidy is common in cancerous cells, and some researchers are suggesting that it may be a cause of cancer.

In any case, aneuploidy leaves obvious birth marks, some of them severely impairing the individual's life and development. Such cases include the Down syndrome or the cri-du-chat syndrome.

Aneuploidy is related to ploidy and polyploidy, and you should also check these subjects for better understanding.


Trisomy involves the presence of an extra chromosome of a certain type. Many trisomy types cause distinct birth affections. The majority of trisomies are fatal to the fetus and cause spontaneous abortion or death immediately after birth. Among those who do not are:

  • The trisomy of the 21 chromosome, known as the Down syndrome
  • The trisomy of the 18 chromosome, known as Edward's syndrome
  • The trisomy of the 13 chromosome, known as Patau's syndrome
  • The trisomy of the 8 chromosome, known as the Warkany syndrome-2.

Some common trisomies that involve a sexual chromosome are the triple X syndrome, Klinefelter's syndrome (extra X chromosome on males) and the XYY syndrome (extra Y chromosome on males).

Most trisomies that do not cause death are, however, severe affections that impair the normal life of the individual.


Monosomy, unlike trisomy, involves the presence of just one chromosome instead of a pair in a cell's nucleus. A special type of monosomy is the partial monosomy, when an arm of a chromosome is not present. The common human monosomies are the Turner syndrome (a missing X chromosome on females) and the cri-du-chat syndrome, the partial monosomy of the 5 chromosome.


  • ICD-10 Q90-Q98
  • ICD-9 758