Cell biology: Selfish B chromosomes unleashed by a dysfunctional chromosome segregation system

A study in the fruit fly Drosophila melanogaster shows that a defective chromosome segregation system allows non-essential B chromosomes to transmit at higher-than-Mendelian frequencies.  A study in the fruit fly Drosophila melanogaster shows that a defective chromosome segregation system allows non-essential B chromosomes to transmit at higher-than-Mendelian frequencies. Higher eukaryotes harbor a range of different selfish genetic elements (SGEs). One type of SGE — B chromosomes — has gained strong research interest over the past few decades. B chromosomes are typified by several key characteristics: they are pervasive in nature, having been observed in thousands of plants and animals; they arise as extra copies from whole regions of chromosomes that make up the organism’s core genome; they are usually diminutive and heterochromatic, expressing few or no functional genes; and, as a result, they provide no benefit to the organism. Because B chromosomes are nonessential, they are prone to loss during cell division. To counter this tendency, many B chromosomes drive, or transmit themselves, from parent to offspring at frequencies higher than are predicted by Mendelian rules

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