懶貓的碎碎念天堂

This is my seminar at  2006/11/28
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Science 21 July 2006:Vol. 313. no. 5785, pp. 320 - 324
A Distinct Small RNA Pathway Silences Selfish Genetic Elements in the Germline
Vasily V. Vagin, Alla Sigova, Chengjian Li, Hervé Seitz, Vladimir Gvozdev, Phillip D. Zamore

Abstract:
       RNA silencing mechanism in eukaryotic cells, such as small interfering RNAs (siRNAs) and microRNAs (miRNAs), which is thought to defend against viruses, regulate gene expression, and protect the genome against selfish genetic elements like retrotransposons and repetitive sequences. Recently, a third type of small RNAs, repeat-associated interfering RNAs (rasiRNAs) have been identified, and be distinct from miRNAs and siRNAs by their longer length, 24 to 29 nt. However, the mechanism of rasiRNAs is not clear. The authors indicated that the rasiRNAs are generated mainly from antisense strand, whereas siRNAs are derived from both sense and antisense strand of their double-strand RNA precursors. In flies, Dicer-1 generates miRNAs and Dicer-2 generates siRNAs, but rasiRNAs have been proposed to be diced from long dsRNA by Dicer-1 or Dicer-2 independent pathway. The simplest interpretation of these data is that rasiRNAs physically associate with Piwi subfamily (Piwi and Aub). Unlike siRNA and miRNA, rasiRNAs lake the 2’, 3’ hydroxyl termini but contain one modified and one unmodified hydroxyl group. These data suggest the rasiRNAs follow a different way to protect fly germline through a silencing mechanism distinct from both miRNA and siRNA pathways.

http://blog.pixnet.net/biingru/trackback/437934 --"Seminar? 沒在怕得啦!"

大學同學寫的一篇好文，

切中正在看 paper 準備 seminar 的我的要害 XD

來到台北參加國際性的大型研討會 -- Asia Pacific Bioinformatic Conferance 2006 已經到了第三天，Conferance 的部分算是結束了，很深刻的一個感覺 -- 自己的英文好濫  >"<聽正統的英文演講已經非常吃力，輪到日本人、韓國人跟香港人口音較重的時候，更是完全呈現 "鴨子聽雷" 狀態.... 又不能睡給他看，所以覺得特別累 QQ發覺生物資訊這一塊領域很多 IT 背景的人，講到程式..公式..語法....又是一陣天旋地轉，我的媽押~~~ 生物背景的人還真的是少之又少內心一直在衡量是否要選擇生物資訊這條路當未來五年的研究方向?嗯......得再好好的想一想.........明天一早還有最後一天的課程，電腦上機實做，希望能學到實用的東西。

(D)RNA = (Deoxy)ribose nucleic acid It has 3 components: a nitrogenous base : purine (A,G) or pyrimidine (T,C) is linked at position 1 on a pentose sugar.a sugar : DNA has 2'-deoxyribose where as RNA has ribose (OH group at potition 2 on pentose ring).and a phosphate : The sugar can be linked by its 5' position to a phosphate group or 3' position to next nucleic acid's phosphate. (direction : 5' --> 3')*DNA contains A,G, C, T, while RNA contains A, G, C, U.

The genome is the complete set of sequences in the genetic material of an organism. It includes the sequence of each chromosome plus any DNA in organelles.  基因體是指整個生物體的遺傳物質，包含染色體序列以及組成蛋白質。ex.  In human, include (1) nulcear genome, (2) mitochondria genome.A gene (cistron) is the segment of DNA specifying production of a polypeptide chain; it includes regions preceding and following the coding region (leader and trailer) as well as intervening sequences (introns) between individual coding segments (exons). Thus a gene is a sequence of DNA that codes for an RNA; in protein-coding genes, the RNA in turn codes for a protein.  基因最簡單的定義就是一段可以轉譯出 RNA 且此 RNA 可以轉錄出蛋白質的 DNA 片段。