Publication Date:
2010-02-23
Description:
Although bisexual reproduction has proven to be highly successful, parthenogenetic all-female populations occur frequently in certain taxa, including the whiptail lizards of the genus Aspidoscelis. Allozyme analysis revealed a high degree of fixed heterozygosity in these parthenogenetic species, supporting the view that they originated from hybridization events between related sexual species. It has remained unclear how the meiotic program is altered to produce diploid eggs while maintaining heterozygosity. Here we show that meiosis commences with twice the number of chromosomes in parthenogenetic versus sexual species, a mechanism that provides the basis for generating gametes with unreduced chromosome content without fundamental deviation from the classic meiotic program. Our observation of synaptonemal complexes and chiasmata demonstrate that a typical meiotic program occurs and that heterozygosity is not maintained by bypassing recombination. Instead, fluorescent in situ hybridization probes that distinguish between homologues reveal that bivalents form between sister chromosomes, the genetically identical products of the first of two premeiotic replication cycles. Sister chromosome pairing provides a mechanism for the maintenance of heterozygosity, which is critical for offsetting the reduced fitness associated with the lack of genetic diversity in parthenogenetic species.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2840635/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2840635/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lutes, Aracely A -- Neaves, William B -- Baumann, Diana P -- Wiegraebe, Winfried -- Baumann, Peter -- Howard Hughes Medical Institute/ -- England -- Nature. 2010 Mar 11;464(7286):283-6. doi: 10.1038/nature08818. Epub 2010 Feb 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20173738" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Chromosome Pairing/*genetics
;
Chromosomes/*genetics
;
Crossing Over, Genetic/genetics
;
Female
;
*Heterozygote
;
Lizards/*genetics
;
Meiosis/genetics
;
Microscopy, Electron, Transmission
;
Oocytes/cytology/physiology/ultrastructure
;
Telomere/genetics
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
