PDF(Pubmed)
Abstract：
Chromosomal translocations can result in phenotypic effects of varying severity, depending on the position of the breakpoints and the rearrangement of genes within the interphase nucleus of the translocated chromosome regions. Balanced translocations are often asymptomatic phenotypically and are typically detected due to a decrease in fertility resulting from issues during meiosis. Robertsonian translocations are among the most common chromosomal abnormalities, often asymptomatic, and can persist in the population as a normal polymorphism. We serendipitously discovered a Robertsonian translocation between chromosome 21 and chromosome 22, which is inherited across three generations without any phenotypic effect, notably only in females. In situ hybridization with alpha-satellite DNAs revealed the presence of both centromeric sequences in the translocated chromosome. The reciprocal translocation resulted in a partial deletion of the short arm of both chromosomes 21, and 22, with the ribosomal RNA genes remaining present in the middle part of the new metacentric chromosome. The rearrangement did not cause alterations to the long arm. The spread of an asymptomatic heterozygous chromosomal polymorphism in a population can lead to mating between heterozygous individuals, potentially resulting in offspring with a homozygous chromosomal configuration for the anomaly they carry. This new karyotype may not produce phenotypic effects in the individual who presents it. The frequency of karyotypes with chromosomal rearrangements in asymptomatic heterozygous form in human populations is likely underestimated, and molecular karyotype by array Comparative Genomic Hybridization (array-CGH) analysis does not allow for the identification of this type of chromosomal anomaly, making classical cytogenetic analysis the preferred method for obtaining clear results on a karyotype carrying a balanced rearrangement.
摘要：
染色体易位可导致不同严重程度的表型效应，取决于断点的位置和易位染色体区域相间核内基因的重排。平衡易位通常在表型上是无症状的,并且通常由于减数分裂期间的问题导致的生育力降低而被检测到。罗伯逊易位是最常见的染色体异常，通常无症状，并且可以作为正常多态性在人群中持续存在。我们偶然发现了21号染色体和22号染色体之间的罗伯逊易位，它在三代之间遗传而没有任何表型效应，尤其是女性。与α-卫星DNA的原位杂交揭示了易位染色体中存在两个着丝粒序列。相互易位导致21号和22号染色体的短臂部分缺失，核糖体RNA基因保留在新的中间染色体的中间部分。重新排列并没有引起长臂的改变。群体中无症状杂合染色体多态性的传播可导致杂合个体之间的交配，可能导致后代携带异常的纯合染色体构型。这种新的核型可能不会在呈现它的个体中产生表型效应。人类群体中无症状杂合形式的染色体重排的核型频率可能被低估了，和分子核型通过阵列比较基因组杂交（阵列CGH）分析不允许鉴定这种类型的染色体异常，使经典的细胞遗传学分析成为获得带有平衡重排的核型明确结果的首选方法。
