At present, thousands of animals and plant species have their genomes sequenced but there are still some portions missing such as the highly repetitive DNA. In the entire mystery of the genome, there are centromeres compartments, which are vital chromosomal regions permitting cells to appropriately transfer chromosome when dividing. According to the study conducted by the Mellone lab at the University of Connecticut and the Larracuente lab at the University of Rochester, they used both next-generation sequencing technology plus high-resolution and molecular microscopy techniques to find out the sequences of all centromeres of Drosophila melanogaster, as it is a powerful model commonly used in biomedical research.
Since a century, the centromeres have been observable under the microscope, but nothing much is known about its sequencing at the DNA level owing to the trouble looking for repetitive DNA using conventional sequencing technologies. For sequencing a genome, the DNA is fragmented into readable units and later assembled back into contiguous sequences resembling the genome just like a jigsaw puzzle in terms of a computational process. In unique DNA sequences or genes, it seems to work well but in the case of identical regions, it gets difficult to figure out where to fit. In order to resolve this issue, the researchers combined methods including DNA sequencing, purification of centromere segments sticking to centromere-specific histone protein, and snapping chromatin fibers with high-resolution microscopy.
With the help of all the method, a complete, intact image of the fly’s centromeres could be seen that was earlier found to be hidden in the highly repetitive sequences. The complex DNA sequences could help unfold the keys to centromeres function and chromosomal segregation. The transposable elements, which are jumping sequences, are higher in centromeres. The retroelements are the type of transposable elements found mostly in the parasites. The fruit fly and Drosophila simulans showed G2/Jockey-3, a retroelement, to be present in all its centromeres. These selfish DNA constituents may have a role in the centromere function in fungi, plants, mammals, and more. The fruit fly centromere sequences in hand can help leverage it understand the overall centromere function and evolution.