Contrasting levels of DNA polymorphism at the autosomal and X-linked visual color pigment loci in humans and squirrel monkeys.
Contrasting levels of DNA polymorphism at the autosomal and X-linked visual color pigment loci in humans and squirrel monkeys.
复制标题
人类和松鼠猴常染色体和 X 连锁视觉色素位点 DNA 多态性水平的对比。
DOI：
10.1093/oxfordjournals.molbev.a025941
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发表时间：
1998
影响因子：
10.7
通讯作者：
Li,WH
中科院分区：
文献类型：
--
作者：
Shimmin,LC;Miller,J;Tran,HN;Li,WH
已知x连锁的颜色色素（视蛋白）位点在松鼠猴和其他新大陆猴中具有高度多态性。为了了解常染色体（蓝色）视蛋白位点是否也是如此，我们获得了32个松鼠猴和30个人类蓝色视蛋白基因序列。在松鼠猴和人类样本中均未发现氨基酸多态性，这与x连锁视蛋白位点的情况相反。这种多态性水平的鲜明对比可能是由于常染色体和x连锁位点之间基因表达的差异。在x连锁位点，杂合子优势可以发生，因为由于x失活，杂合子中的两个等位基因在不同的锥体细胞中表达，产生两种类型的锥体细胞，而在常染色体位点，杂合子优势不能发生，因为杂合子中的两个等位基因在相同的锥体细胞中表达，只产生一种类型的锥体细胞（即，表型上为纯合子）。从序列数据中，估计核苷酸多样性水平（pi，即每个位点的核苷酸差异数）：对于人类样本，编码区pi = 0.00% /非简并位点，0.00% /二次简并位点，0.04% /四次简并位点，内含子4每位点0.01%；对于松鼠猴样本，编码区每个非退化位点的PI = 0.00%，每个二次退化位点的PI = 0.00%，每个四次退化位点的PI = 0.15%，内含子4的PI = 0.17%。研究人员还对普通黑猩猩、侏儒黑猩猩、大猩猩、卷尾猴和吼猴的蓝色视蛋白基因进行了测序。对视蛋白功能至关重要的特征在所有已知的哺乳动物序列中都是保守的。然而，平均而言，螺旋间环实际上比跨膜螺旋区更保守。此外，这些序列数据和其他一些基因的数据表明，普通黑猩猩和侏儒黑猩猩的关系并不密切，它们的分化数据是人类-黑猩猩分化日期的三分之一到二分之一。
The X-linked color pigment (opsin) locus is known to be highly polymorphic in the squirrel monkey and other New World monkeys. To see whether this is also the case for the autosomal (blue) opsin locus, we obtained 32 squirrel monkey and 30 human blue opsin gene sequences. No amino acid polymorphism was found in either the squirrel monkey sample or the human sample, contrary to the situation at the X-linked opsin locus. This sharp contrast in the level of polymorphism might be due to differences in gene expression between the autosomal and the X-linked loci. At the X-linked locus, heterozygote advantage can occur because, owing to X-inactivation, the two alleles in a heterozygote are expressed in different cone cells, producing two types of cone cell, whereas at the autosomal locus, heterozygote advantage cannot occur because the two alleles in a heterozygote are expressed in the same cone cells, producing only one type of cone cell (i.e., phenotypically a homozygote). From the sequence data, the levels of nucleotide diversity (pi, i.e., the number of nucleotide differences per site) are estimated: for the human sample, pi = 0.00% per nondegenerate site, 0.00% per twofold degenerate site, and 0.04% per fourfold degenerate site in the coding regions and 0.01% per site in intron 4; for the squirrel monkey sample, pi = 0.00% per nondegenerate site, 0.00% per twofold degenerate site, and 0.15% per fourfold degenerate site in the coding regions and 0.17% per site in intron 4. The blue opsin genes from the common and pygmy chimpanzees, the gorilla, the capuchin, and the howler monkey were also sequenced. Features critical to the function of the opsin are well conserved in all known mammalian sequences. However, the interhelical loops are, on average, actually more conservative than the transmembrane helical regions. In addition, these sequence data and those from some other genes indicate that the common and pygmy chimpanzees are not closely related, their divergence data being from one third to one half the date of the human-chimpanzee divergence.