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研究发现单细胞生物四膜虫有7种性别

如果你认为人类之间的性别战很复杂,请设身处地为单细胞生物四膜虫考虑一下——它有七种性别。

如果你认为人类之间的性别战很复杂,请设身处地为单细胞生物四膜虫考虑一下——它有七种性别。

人类繁衍后代是靠一男一女,生出来的孩子要么是男要么是女,虽然偶尔会有变异,但四膜虫繁衍后代要复杂的多。它们的后代可能与父母不属于同一种性别,可以是七种性别中的任意一种。

根据最新发表在《PLoS Biology》上的报告,研究人员找到方法根据DNA判断性别,发现四膜虫的性别选择是随机的。四膜虫有两类细胞核,正常细胞核包含性别基因,另一种细胞核主要用于繁殖,它包含了所有7种性别基因的不完整版本,通过粘贴剪切组合成一个完整的基因。重新排列的新DNA成为后代正常细胞核的一部分,决定其性别类型。

研究人员认为,这项研究有助于那些不同于男女性别的人类认识自己。

性别战:在博弈论中,性别战是有两个参与者的协调博弈的一个例子。假想如下的情景:有一对夫妇度周末,丈夫最想去的是看篮球比赛,妻子最想去的是逛街,但他们都想呆在一起而不是分开各做各的。如果他们不相互商量,会如何度过周末呢?

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ScienceShot: Seven Sexes on the Menu

If you thought the battle of the genders was complicated, try having seven sexes. When Tetrahymena, a single-celled creature covered in cilia, mates, the offspring isn't necessarily the same sex as either parent—it can be any of seven. Now, researchers have figured out the complex dance of DNA that determines the offspring's sex, and it's a random selection, they report today in PLOS Biology. Each Tetrahymena has a gene for its own sex—or mating type—in its regular nucleus, but it also carries a second nucleus used only for reproduction. This "germline nucleus" contains incomplete versions of all seven mating type genes, which are cut and pasted together until one complete gene remains and the other six have been deleted. The newly rearranged DNA becomes part of the offspring's regular nucleus, determining its mating type. Because the mating type gene helps Tetrahymena recognize others of a different sex, the researchers say that the finding could shed light on how other cells, including those in humans, recognize those that are different from themselves.

Selecting One of Several Mating Types through Gene Segment Joining and Deletion in Tetrahymena thermophila

PLoS Biol., March 26, 2013 | doi:10.1371/journal.pbio.1001518

The unicellular eukaryote Tetrahymena thermophila has seven mating types. Cells can mate only when they recognize cells of a different mating type as non-self. As a ciliate, Tetrahymenaseparates its germline and soma into two nuclei. During growth the somatic nucleus is responsible for all gene transcription while the germline nucleus remains silent. During mating, a new somatic nucleus is differentiated from a germline nucleus and mating type is decided by a stochastic process. We report here that the somatic mating type locus contains a pair of genes arranged head-to-head. Each gene encodes a mating type-specific segment and a transmembrane domain that is shared by all mating types. Somatic gene knockouts showed both genes are required for efficient non-self recognition and successful mating, as assessed by pair formation and progeny production. The germline mating type locus consists of a tandem array of incomplete gene pairs representing each potential mating type. During mating, a complete new gene pair is assembled at the somatic mating type locus; the incomplete genes of one gene pair are completed by joining to gene segments at each end of germline array. All other germline gene pairs are deleted in the process. These programmed DNA rearrangements make this a fascinating system of mating type determination.

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