{"doi":"10.1093/g3journal/jkac264","title":"Mitotic exchange in female germline stem cells is the major source of <i>Sex Ratio</i> chromosome recombination in <i>Drosophila pseudoobscura</i>","abstract":"Sex Ratio chromosomes in Drosophila pseudoobscura are selfish X chromosome variants associated with 3 nonoverlapping inversions. In the male germline, Sex Ratio chromosomes distort the segregation of X and Y chromosomes (99:1), thereby skewing progeny sex ratio. In the female germline, segregation of Sex Ratio chromosomes is mendelian (50:50), but nonoverlapping inversions strongly suppress recombination establishing a 26-Mb haplotype (constituting ∼20% of the haploid genome). Rare crossover events located between nonoverlapping inversions can disrupt this haplotype, and recombinants have sometimes been found in natural populations. We recently reported on the first lab-generated Sex Ratio recombinants occurring at a rate of 0.0012 crossovers per female meiosis. An improved experimental design presented here reveals that these recombination events were at least 4 times more frequent than previously estimated. Furthermore, recombination events were strongly clustered, indicating that the majority arose from mitotic exchange in female germline stem cells and not from meiotic crossing-over in primary oocytes. Finally, asymmetric recovery of complementary recombinants was consistent with unequal exchange causing the recombination-induced viability defects. Incorporating these experimental results into population models for Sex Ratio chromosome evolution provided a substantially better fit to natural population frequencies and allowed maintenance of the highly differentiated 26-Mb Sex Ratio haplotype without invoking strong epistatic selection. This study provides the first estimate of spontaneous mitotic exchange for naturally occurring chromosomes in Drosophila female germline stem cells, reveals a much higher Sex Ratio chromosome recombination rate, and develops a mathematical model that accurately predicts the rarity of recombinant Sex Ratio chromosomes in natural populations.","journal":"G3 Genes Genomes Genetics","year":2022,"id":295902,"datarank":0.10397207708399181,"base_score":0.6931471805599453,"endowment":0.6931471805599453,"self_citation_contribution":0.10397207708399181,"citation_network_contribution":0.0,"self_endowment_contribution":0.10397207708399181,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":1,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9426,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":982110,"name":"Spencer Koury","orcid":"0000-0002-9782-8343","position":0,"is_corresponding":true}],"reference_count":30,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T00:31:12.531553Z","pmid":"36194019","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}