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Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole ( trisomy 21) or part (such as due to translocations ). The effects of the extra copy varies greatly from individual to individual, depending on the extent of the extra copy, genetic background ...
Translocation Down syndrome. The extra chromosome 21 material may also occur due to a Robertsonian translocation in 2–4% of cases. In this translocation Down syndrome, the long arm of chromosome 21 is attached to another chromosome, often chromosome 14. In a male affected with Down syndrome, it results in a karyotype of 46XY,t(14q21q).
For example, carriers of Robertsonian translocations involving chromosome 21 have a higher risk of having a child with Down syndrome. This is known as a 'translocation Downs'. This is due to a mis-segregation (nondisjunction) during gametogenesis. The mother has a higher (10%) risk of transmission than the father (1%).
Translocation Down syndrome: This happens when genetic material from chromosome 21 attaches to another chromosome. There are no known environmental factors thought to...
In unbalanced forms, Robertsonian translocations cause chromosomal deletions or addition and result in syndromes of multiple malformations, including trisomy 13 (Patau syndrome) and trisomy 21 (Down syndrome). The most frequent forms of Robertsonian translocations are between chromosomes 13 and 14, 14 and 21, and 14 and 15.
These cases are called translocation Down syndrome. Researchers believe that extra copies of genes on chromosome 21 disrupt the course of normal development, causing the characteristic features of Down syndrome and the increased risk of medical problems associated with this disorder.
Patau syndrome can also occur when part of chromosome 13 becomes attached to another chromosome (translocated) before or at conception in a Robertsonian translocation. Affected people have two copies of chromosome 13, plus extra material from chromosome 13 attached to another chromosome.
Down syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with developmental delays, characteristic physical features, and mild to moderate intellectual disability. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8- or 9 ...
The Philadelphia chromosome or Philadelphia translocation ( Ph) is a specific genetic abnormality in chromosome 22 of leukemia cancer cells (particularly chronic myeloid leukemia (CML) cells). This chromosome is defective and unusually short because of reciprocal translocation, t (9;22) (q34;q11), of genetic material between chromosome 9 and ...
Transient myeloproliferative disease (TMD) occurs in a significant percentage of individuals born with the congenital genetic disorder, Down syndrome. It may occur in individuals who are not diagnosed with the syndrome but have some hematological cells containing genetic abnormalities that are similar to those found in Down syndrome.
