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A Robertsonian translocation results when the long arms of two acrocentric chromosomes fuse at the centromere and the two short arms are lost. If, for example, the long arms of chromosomes 13 and 14 fuse, no significant genetic material is lost—and the person is completely normal in spite of the translocation.
The extra chromosome 21 material that causes Down syndrome may be due to a Robertsonian translocation. The long arm of chromosome 21 is attached to the long arm of another chromosome, often chromosome 14 [46,XX,t(14;21)] or itself [called an isochromosome, 45,XX,t(21;21)(q10;q10)] as seen in the translocation karyotype figure.
Chromosomal reciprocal translocation of the 4th and 20th chromosome. In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal, and Robertsonian translocation.
The extra chromosome 21 material may also occur due to a Robertsonian translocation in 2–4% of cases. [91] [101] In this translocation Down syndrome, the long arm of chromosome 21 is attached to another chromosome, often chromosome 14. [102] In a male affected with Down syndrome, it results in a karyotype of 46XY,t(14q21q).
The resulting dicentric chromosomes are highly unstable, giving rise to chromosomal translocations, deletions and amplifications, such as the Robertsonian translocation. This results in broken, deleted gene products of dicentric fragments. [1]
William Rees Brebner Robertson (31 May 1881 - 15 March 1941) was an American zoologist and early cytogeneticist who discovered the chromosomal rearrangement named in his honour, Robertsonian translocation, the most common structural chromosomal abnormalities seen in humans that result in syndromes of multiple malformations, including trisomy 13 Patau syndrome and trisomy 21 Down syndrome.
There are two main types of translocations: Reciprocal translocation: Segments from two different chromosomes have been exchanged. Robertsonian translocation: An entire chromosome has attached to another at the centromere - in humans, these only occur with chromosomes 13, 14, 15, 21, and 22.
Robertsonian translocation; T. T(11:14) This page was last edited on 31 October 2022, at 20:55 (UTC). Text is available under the Creative Commons Attribution ...