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Flat Volcano plot

Hello everyone I have performed differential expression analysis on human dataset (GPL14550 Agilent-028004 SurePrint G3 Human GE 8x60K Microarray (Probe Name Version)). I have 12 samples of Th1 and Th2 sample type. At the end I visualized the top genes using volcano plot and it came out weird as shown in image. Please help me to figure it out. Volcano plot

differential r volcano expression plot
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written by Vinesh • Vinesh

It probably means that you have only adjusted p-values very close to 1, so no differential expression. What is the output of a summary() when you run it on the adjusted p-value column of the results?

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written by ATpoint ATpoint

This is the output of summary(tab$adj.P.Val)

Min. 0.994 1st Qu. 0.9994 Median 0.9994 Mean 0.9994 3rd Qu. 0.9994 Max. 0.9994

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written by Vinesh • Vinesh

There you go, no differential genes. The study could be underpowered or there are no DEGs, or batch effects make dispersion large.

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written by ATpoint ATpoint

okay thank you so much for the explanation

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written by Vinesh • Vinesh

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