Mapping meiotic crossovers in Drosophila using combinatorial indexing and whole-genome sequencing.

Crossovers ensure proper segregation of homologous chromosomes during meiosis. Homologous recombination repairs double-strand DNA breaks and can result in crossover or non-crossover outcomes. Crossover patterning regulates which double-strand breaks become crossovers, as there are many more double-strand breaks than crossovers. The model organism Drosophila melanogaster is typically used to study crossover patterning with phenotypic markers for recessive alleles on a single chromosome. However, this leads to a low resolution of recombination frequency and requires researchers to screen thousands of flies visually. Sci-L3 combines LIANTI, a type of linear whole genome amplification, with unique DNA sequences used as barcodes so that sequencing results can be attributed to specific cells. Developing sci-L3 to be used with Drosophila will allow for next-generation sequencing to be used in place of phenotypic markers when studying crossovers. Sci-L3 of wild-type Drosophila results in DNA fragments of varying lengths. Similar linear amplification techniques can be used to sequence crossover events on all four daughter cells from one meiotic event. Using sci-L3, thousands of meiotic events can be sequenced rapidly at a fraction of the cost of whole genome sequencing.Bachelor of Scienc