Monosomy
Encyclopedia
Monosomy is a form of aneuploidy
Aneuploidy
Aneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...

 with the presence of only one chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

 (instead of the typical two in humans) from a pair. Partial monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies.

Human monosomy

Human conditions due to monosomy:
  • Turner syndrome
    Turner syndrome
    Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

     - Women with Turner syndrome
    Turner syndrome
    Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

     typically have one X chromosome instead of the usual two sex chromosomes. Turner syndrome is the only full monosomy that is seen in humans—all other cases of full monosomy are lethal and the individual will not survive development.
  • Cri du chat
    Cri du chat
    Cri du chat syndrome, also known as chromosome 5p deletion syndrome, 5p minus syndrome or Lejeune’s syndrome, is a rare genetic disorder due to a missing part of chromosome 5. Its name is a French term referring to the characteristic cat-like cry of affected children. It was first described by...

     syndrome -- (French for "cry of the cat" after the distinctive noise by affected persons' malformed larynx
    Larynx
    The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

    ) a partial monosomy caused by a deletion of the end of the short p (from the word petit, French for small) arm of chromosome 5
  • 1p36 Deletion Syndrome
    1p36 Deletion Syndrome
    1p36 deletion syndrome is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features...

     -- a partial monosomy caused by a deletion at the end of the short p arm of chromosome 1
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