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Robertsonian translocation (ROB) is a chromosomal abnormality where the entire long arms of two different chromosomes become fused to each other. It is the most common form of chromosomal translocation in humans, affecting 1 out of every 1,000 babies born. [1] It does not usually cause medical problems, though some people may produce gametes ...
Chromosomal translocation. 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.
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.
Dicentric chromosome. A dicentric chromosome is an abnormal chromosome with two centromeres. It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments. [1] The formation of dicentric chromosomes has been ...
The extra chromosome 21 material may also occur due to a Robertsonian translocation in 2–4% of cases. [90] [100] In this translocation Down syndrome, the long arm of chromosome 21 is attached to another chromosome, often chromosome 14. [101] In a male affected with Down syndrome, it results in a karyotype of 46XY,t(14q21q).
Short acrocentric p-arms contain little genetic material and can be translocated without significant harm, as in a balanced Robertsonian translocation. In addition to some protein coding genes, human acrocentric p-arms also contain Nucleolus organizer regions (NORs), from which ribosomal RNA is transcribed.
Isochromosome in which the arms are mirror copies of each other. An isochromosome is an unbalanced structural abnormality in which the arms of the chromosome are mirror images of each other. [1] The chromosome consists of two copies of either the long (q) arm or the short (p) arm because isochromosome formation is equivalent to a simultaneous ...
Robertsonian translocations are variations in the numbers of chromosomes that arise from either: the fusion of two acrocentric chromosomes into a single chromosome with two arms, causing a reduction in the haploid number, or conversely; or the fission of one chromosome into two acrocentric chromosomes, in this case increasing the haploid number ...