Chromosome 20
Alagille syndrome in 7% of cases it is associated with small deletions of genetic material on chromosome 20, in a region known as 20p12. This region includes the JAG1 gene, which participates in signaling between neighboring cells during embryonic development. This signaling influences how cells are used to build body structures in the developing embryo. As a result, errors can occur during development, which especially affect the heart such as pulmonary stenosis, which consists of poor circulation of the heart to the lungs, bile ducts in the liver (gastric disorders, jaundice), the spine and certain facial features. . The severity of symptoms varies widely from one individual to another.
Cancer. Changes on chromosome 20 have been identified in several types of cancer. These chromosomal abnormalities are somatic. Deletions involving the long arm (q) of chromosome 20 appear to be common in blood-related cancers, such as leukemia and lymphoma. Deletions of this chromosomal region have also been identified in other disorders of the blood and bone marrow, including polycythemia vera (which causes an overproduction of red blood cells) and myelodysplastic syndrome (which leads to a shortage of healthy blood cells).
Ring chromosome 20 syndrome. Symptoms may include low development or a moderate mental disability, but especially this disorder affects brain development causing seizures, which are usually partial; that is, they only occur in certain areas of the brain.
It is not well understood how the ring chromosome causes the signs and symptoms of this syndrome. In some affected people, genes near the ends of chromosome 20 are removed when the ring chromosome is formed. Researchers suspect that the loss of these genes may be responsible for epilepsy and other health problems. However, other affected individuals do not have genetic deletions associated with the ring chromosome. In these people, the ring chromosome may change the activity of certain genes on chromosome 20, or it may be unable to copy (replicate) normally during cell division.
Deletions or duplications of genetic material on chromosome 20 can have a variety of effects, including intellectual disability, delayed development, distinctive facial features, skeletal abnormalities and heart defects. Several different changes in the structure of chromosome 20 have been reported. These include an additional segment of the short (p) or long (q) arm of the chromosome in each partial trisomy cell 20p or 20q or a missing segment of the short or long arm of the chromosome in each partial monosomy cell 20p or 20q.
