一種全為雌性的鞭尾蜥物種（由有不同性別的種之間的雜交形成）的存在自1962年以來就已為人們所知了,，但它是怎樣用一整套體細(xì)胞染色體組來產(chǎn)生成熟卵的卻仍不清楚,，同樣其維持遺傳多樣性的機(jī)制也不清楚。據(jù)Nature 3月11日最新報(bào)道,，Lutes等人發(fā)現(xiàn),，在該物種中,，減數(shù)分裂開始時(shí)的染色體數(shù)量是有不同性別物種的兩倍，而且配對和重組發(fā)生在遺傳相同的姐妹染色體之間,，而不是發(fā)生在同源染色體之間,。(生物谷Bioon.com)

生物谷推薦原文出處：
Nature vol.464 (7286), (11 Mar 2010)  doi:10.1038/nature08818

Sister chromosome pairing maintains heterozygosity in parthenogenetic lizards
Aracely A. Lutes1,2, William B. Neaves1,3, Diana P. Baumann1, Winfried Wiegraebe1 & Peter Baumann1,2,4

1 Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
2 Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
3 University of Missouri Kansas City, School of Medicine, Kansas City, Missouri 64110, USA
4 Howard Hughes Medical Institute, Kansas City, Missouri 64110, USA

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 species1, 2, 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.