What Is Chromosome Translocation?

A change in the position of a chromosome segment is called a translocation (represented by t). It is accompanied by a change in gene position. When a translocation occurs within a chromosome, it is called a shift or intrachromosomal translocation. When a translocation occurs between two homologous or non-homologous chromosomes, it is called an interchromosomal translocation. ). The translocation of homologous chromosomes mainly occurred on chromosomes 10 and 14.

Chromosome translocation

Robertsonian translocation is a special form of mutual translocation. The two proximal centromeres (D / D, D / G, G / G) break at or near the centromere to form two derived chromosomes. One consists of the long arms of the two, with almost all genetic material; the other consists of the short arms of the two, a small chromosome consisting of the two short arms. It is often lost due to a lack of centromeres or because it consists almost entirely of heterochromatin. Its presence does not cause phenotypic abnormalities.

Roche translocations are also commonly referred to as centric fusions. During meiosis, due to the loss of the small chromosome consisting of two short arms, only three chromosomes are involved in the association to form a trivalent body. There are three ways to separate the trivalent body, namely the alternating form (homologous centromeres each go to one pole, resulting in a normal and a balanced translocation gamete), ortho-1 and ortho-2. Homologous centromeres all move to the first level, that is, the translocation chromosome moves to the same pole as a normal chromosome, and as a result, both form dimorphic (duplicate) or apophyte gametes. This gamete forms a trisomy or monomeric zygote after fertilization. Because gametes that are deficient are usually lethal, there are actually only three types of gametes that may be involved in fertilization: normal, balanced translocation, and trisomy. Although the carrier of Roche translocation has only 45 chromosomes, it has no phenotypic abnormalities except for occasional male infertility. This is because the translocation chromosome includes almost all of the two long arms, there is no substantial loss of genes, and the two short arms that are lost are almost all structural heterochromatin.