请问假基因也能表达吗 ?1. pls read the following text cited from internet. It is very interesting I think. " By definition, pseudogenes lack a function. However, the classification of pseudogenes generally relies on computational analysis of genomic sequences using complex algorithms.This has led to the incorrect identification of pseudogenes. For example the functional, chimeric gene jingwei in Drosophila was once thought to be a processed pseudogene." " Types and origin of pseudogenes: There are three main types of pseudogenes, all with distinct mechanisms of origin and characteristic features. The classifications of pseudogenes are as follows: 1. Processed (or retrotransposed) pseudogenes. In higher eukaryotes, particularly mammals, retrotransposition is a fairly common event that has had a huge impact on the composition of the genome. For example, somewhere between 30% - 44% of the human genome consists of repetitive elements such as SINEs and LINEs (see retrotransposons). In the process of retrotransposition, a portion of the mRNA transcript of a gene is spontaneously reverse transcribed back into DNA and inserted into chromosomal DNA. Although retrotransposons usually create copies of themselves, it has been shown in an in vitro system that they can create retrotransposed copies of random genes, too.Once these pseudogenes are inserted back into the genome, they usually contain a poly-A tail, and usually have had their introns spliced out; these are both hallmark features of cDNAs. However, because they are derived from a mature mRNA product, processed pseudogenes also lack the upstream promoters of normal genes; thus, they are considered "dead on arrival", becoming non-functional pseudogenes immediately upon the retrotransposition event. However, occasionally these insertions contribute exons to existing genes and usually via alternatively spliced transcripts. A further characteristic of processed pseudogenes is common truncation of the 5' end relative to the parent sequence, which is a result of the relatively non-processive retrotransposition mechanism that creates processed pseudogenes. 2. Non-processed (or duplicated) pseudogenes. Gene duplication is another common and important process in the evolution of genomes. A copy of a functional gene may arise as a result of a gene duplication event and subsequently acquire mutations that cause it to become nonfunctional. Duplicated pseudogenes usually have all the same characteristics of genes, including an intact exon-intron structure and promoter sequences. The loss of a duplicated gene's functionality usually has little effect on an organism's fitness, since an intact functional copy still exists. According to some evolutionary models, shared duplicated pseudogenes indicate the evolutionary relatedness of humans and the other primates. 3. Disabled genes, or unitary pseudogenes. Various mutations can stop a gene from being successfully transcribed or translated, and a gene may become nonfunctional or deactivated if such a mutation becomes fixed in the population. This is the same mechanism by which non-processed genes become deactivated, but the difference in this case is that the gene was not duplicated before becoming disabled. Normally, such gene deactivation would be unlikely to become fixed in a population, but various population effects, such as genetic drift, a population bottleneck, or in some cases, natural selection, can lead to fixation. The classic example of a unitary pseudogene is the gene that presumably coded the enzyme L-gulono-γ-lactone oxidase (GULO) in primates. In all mammals studied besides primates (except guinea pigs), GULO aids in the biosynthesis of Ascorbic acid (vitamin C), but it exists as a disabled gene (GULOP) in humans and other primates.[13][14] Another interesting and more recent example of a disabled gene, which links the deactivation of the caspase 12 gene (through a nonsense mutation) to positive selection in humans. Pseudogenes can complicate molecular genetic studies. For example, a researcher who wants to amplify a gene by PCR may simultaneously amplify a pseudogene that shares similar sequences. This is known as PCR bias or amplification bias. Similarly, pseudogenes are sometimes annotated as genes in genome sequences. Processed pseudogenes often pose a problem for gene prediction programs, often being misidentified as real genes or exons. It has been proposed that identification of processed pseudogenes can help improve the accuracy of gene prediction methods. It has also been shown that the parent sequences that give rise to processed pseudogenes lose their coding potential faster than those giving rise to non-processed pseudogenes."之前测序时也碰到过pseudogene，很麻烦的东西，只有找真基因和假基因的差异处酶切回收后测序。相对来说我这个算是小case啦，要是做mRNA表达分析假基因可就是大麻烦啦。 pseudogene的研究主要以processed pseudogene为主，各种争论五花八门，至少到今天为止还没有一篇能站住脚的文献论证假基因是真正有功能的(Toshiaki Watanabe和ERIC.J.DEVOR分别报道过假基因能能包含着microRNA母本，不知道这算不算是有功能)。另外一些学者们推测pseudogene可以稳定其真基因的mRNA甚至可以调控翻译，但都没有明确的证据。 03年，Shinji Hirotsune研究成果在Nature发表，称“假基因可以调控其真基因的mRNA稳定性”，06年Todd A. Gray的PNAS文章提出质疑，他们发现之前的假基因被高度甲基化——既不表达也不稳定其真基因的mRNA。就这个问题，Jeannie T. Lee、Adam Pavlicek、Satoko Kaneko先后撰文做过探讨，但他们都是比较支持假基因有功能的。 查看更多
关于叶片周期通道建立，如何快速提取周期通道?我的想法是，先通过geometry-- creat/modify curves-- Circle from Center and 2 Points建立旋转周期段的圆弧(注意设置好起始角度，和终止角度，半径也要合适)，再建立这段圆弧的端点，连接圆弧中心点和圆弧端点成两条直线（比如我上次的问题，两条直线的角度为120），再拉伸这两条直线成面，用这两个面分割几何【这可以通过repair geometry-- Build Topology后删除多余面】再补上对称面。不知道有没有更好的方法~【 ! 】所有操作都在icemcfd中实现，用 cad 软件或许更加简单…… 查看更多
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