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gaohui8888金蟲 (正式寫手)
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[交流]
密碼子偏好性PR2(Parity Rule 2)繪圖
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PR2(Parity Rule 2)繪圖分析如何做?PR2(Parity Rule 2),有的人也叫奇偶偏好分析。 我選取一個病毒的46個不同毒株的編碼區(qū)序列,即有46個核苷酸序列。 現在要用這46個序列對這個病毒進行PR2(Parity Rule 2)繪圖。 根據文獻,需要計算A3,T3,C3,G3的含量(fraction),再算A/(A + T)]和G/(G + C)。而且文獻里面提到要用下列氨基酸的這些密碼子的A3,T3,C3,G3值更有說服力:four-codon amino acids:alanine, arginine4 (CGA,CGT, CGG, CGC), glycine, leucine4 (CTA, CTT, CTG, CTC), proline,serine4 (TCA, TCT, TCG, TCC), threonine, and valine. 存在的問題: 1、每個基因的A3,T3,C3,G3如何計算?是否有軟件可以計算? 2、4個同義密碼子編碼的氨基酸,有8個(alanine, arginine4 (CGA,CGT, CGG, CGC), glycine, leucine4 (CTA, CTT, CTG, CTC), proline,serine4 (TCA, TCT, TCG, TCC), threonine, and valine),是否把這8個氨基酸的A3,T3,C3,G3值分別進行平均,得到一個基因的A3,T3,C3,G3? 原始的參考文獻里面是這么介紹PR2(Parity Rule 2): 標題:Near Homogeneity of PR2-Bias Fingerprints in the Human Genome and Their Implications in Phylogenetic Analyses PR2-bias Plot的介紹. Plotting AT-bias [A/(A + T)] as the ordinate and GC-bias [G/(G + C)] as the abscissa shows PR2-biases as a unique pattern (Sueoka 1995). The center of the plot, where both coordinates are 0.5, is the place where A=T and G=C (PR2). A vector from the center represents the extent and direction of biases from PR2. PR2 bias plots are particularly informative when PR2 biases at the third codon position of the four-codon amino acids of individual genes are plotted. In this case, “A3/(A3 + T3) | 4” and “G3/(G3 + C3) | 4” are plotted as theordinate and abscissa, respectively. Here “| 4” denotes the four-codon amino acids. The four-codon amino acids are alanine, arginine4 (CGA, CGT, CGG, CGC), glycine, leucine4 (CTA, CTT, CTG, CTC), proline, serine4 (TCA, TCT, TCG, TCC), threonine, and valine. |
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