Other Definitions
chromosome (dict)

Chromosome

For information about chromosomes in genetic algorithms, see Chromosome (genetic algorithm).

Chromosomes in eukaryotes

Chromosomes in bacteria

Chromatin

• Euchromatin, which consists of DNA that is active, e.g., expressed as protein.
• Heterochromatin, which consists of mostly inactive DNA. It seems to serve structural purposes during the chromosomal stages. Heterochromatin can be further distinguished into two types:
• Constitutive heterochromatin, which is never expressed. It is located around the centromere and usually contains repetitive sequences.
• Facultative heterochromatin, which is sometimes expressed.

Chromosomes in different species

Karyotype

Human chromosome

Chromosomal aberrations

• Cri du chat syndrome, which is caused by the deletion of part of the short arm of chromosome 5. Victims make high-pitched cries that sound like a cat. They have wide-set eyes, a small head and jaw and are mentally retarded.
• Wolf-Hirschhorn syndrome, which is caused by partial deletion of the short arm of chromosome 4. It is characterized by severe growth retardation and mental defect.
• Down syndrome (extra chromosome 21). This is also known as mongolism or trisomy 21. Symptoms are decreased muscle tone, asymmetrical skull, slanting eyes and mental retardation.
• Edward's syndrome is the second most common trisomy after Down's Syndrome. It is a trisomy of chromosome 18. Symptoms include mental and motor retardation.
• Patau Syndrome, also called D-Syndrome or trisomy-13. Symptoms somewhat similar to those of trisomy-18.
• Jacobsen syndrome, also called the terminal 11q deletion disorder. A very rare disorder. More information at http://www.11q.org.
• Klinefelters syndrome (XXY). Men with Klinefelter syndrome are usually sterile. They tend to have longer arms and legs and tend to be taller than their peers. Other common symptoms are fatigue, apathy, lack of emotion, and an increased tendency to develop psychiatric disorders.
• Turner syndrome (X instead of XX or XY). In Turner syndrome, female sexual characteristics are present but underdeveloped. People with Turner syndrome often have a short stature, low hairline, abnormal eye features and bone development and a "caved-in" appearance to the chest.
• XYY syndrome
• Triple-X syndrome

See also

• XY sex-determination system
• Genetic deletion

External links

• What Can Our Chromosomes Tell Us?,an accessible and comprehensive look at chromosomes, from the University of Utah's Genetic Science Learning Center
• Try making a karyotype yourself, from the University of Utah's Genetic Science Learning Center
• Kimballs Chromosome pages
• Chromosome News from Genome News Network

• European Chromosome 11q Network
• Eurochromnet, European network for Rare Chromosome Disorders on the Internet

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