Chang B H, Li W H
Center for Demographic and Population Genetics, University of Texas, Houston 77225.
J Mol Evol. 1995 Jan;40(1):70-7. doi: 10.1007/BF00166597.
Using sequence data from the last introns of ZFX and ZFY genes, we previously estimated the male-to-female ratio (alpha) of mutation rate to be close to 6 in higher primates and 1.8 in rodents. As the mutation rate may vary among different regions of the mammalian genome, it is interesting to see whether sequence data from other regions will give similar estimates. In this study, we have determined the partial genomic sequences of the ubiquitin-activating enzyme E1 genes (Ube 1x and Ube 1y for the X-linked and Y-linked homologues, respectively) of mice and rats and two mouse Ube 1y pseudogenes. From the intron sequences of the Ube 1 genes, we calculated the divergence of the Y-linked genes (Y = 0.161) and that of the X-linked genes (X = 0.107) between mouse and rat, and found the Y/X ratio to be 1.50. This ratio led to an estimate of alpha = 2.0 with a 95% confidence interval of (1.0, 3.9). Similar estimates of alpha were obtained if mouse Ube 1y pseudogenes were used instead of the mouse Ube 1y functional gene. These estimates are consistent with our previous estimate for rodents and suggest that the sex ratio of mutation rate in rodents is approximately only one-third of that in higher primates. Our estimate of the divergence time between Ube 1x and Ube 1y supports the view that the two genes separated before the eutherian radiation.
利用ZFX和ZFY基因最后一个内含子的序列数据，我们之前估计在高等灵长类动物中，突变率的雄性与雌性之比（α）接近6，而在啮齿动物中为1.8。由于突变率可能在哺乳动物基因组的不同区域有所变化，因此看看来自其他区域的序列数据是否会给出类似的估计很有意思。在本研究中，我们确定了小鼠和大鼠泛素激活酶E1基因（分别为X连锁和Y连锁同源物的Ube 1x和Ube 1y）以及两个小鼠Ube 1y假基因的部分基因组序列。从Ube 1基因的内含子序列中，我们计算了小鼠和大鼠之间Y连锁基因的分歧度（Y = 0.161）和X连锁基因的分歧度（X = 0.107），并发现Y/X比值为1.50。这个比值得出α = 2.0的估计值，其95%置信区间为(1.0, 3.9)。如果使用小鼠Ube 1y假基因而非小鼠Ube 1y功能基因，也能得到类似的α估计值。这些估计值与我们之前对啮齿动物的估计一致，表明啮齿动物中突变率的性别比大约仅为高等灵长类动物的三分之一。我们对Ube 1x和Ube 1y之间分歧时间的估计支持了这两个基因在真兽类辐射之前就已分离的观点。
