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Reciprocal translocations are usually an exchange of material between non-homologous chromosomes and occur in about 1 in 491 live births. [3] Such translocations are usually harmless, as they do not result in a gain or loss of genetic material, though they may be detected in prenatal diagnosis.
The grasshopper Melanoplus femur-rubrum was exposed to an acute dose of X-rays during each individual stage of meiosis, and chiasma frequency was measured. [23] Irradiation during the leptotene-zygotene stages of meiosis (that is, prior to the pachytene period in which crossover recombination occurs) was found to increase subsequent chiasma ...
In translocation heterozygote, however, certain patterns of chromosome segregation during meiosis produce genetically unbalanced gametes that at fertilization become deleterious to the zygote. In a translocation heterozygote, the two haploid sets of chromosomes do not carry the same arrangement of genetic information.
During this time, recombination can take place via crossing over of sections of the paternal and maternal chromatids and leads to reciprocal recombination or non-reciprocal recombination. [1] Unequal crossing over requires a measure of similarity between the sequences for misalignment to occur.
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.
This is an accepted version of this page This is the latest accepted revision, reviewed on 19 December 2024. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
At a given chiasma, an exchange of genetic material can occur between both chromatids, what is called a chromosomal crossover, but this is much more frequent during meiosis than mitosis. [1] In meiosis , absence of a chiasma generally results in improper chromosomal segregation and aneuploidy .
Duplications arise from an event termed unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes. The chance of it happening is a function of the degree of sharing of repetitive elements between two chromosomes. The products of this recombination are a duplication at the site of the exchange and a reciprocal ...