Nadeau et al., (Royal Soc. B. 2007) Reconstructed dN/dS ratios for genes involved in sexually dimorphic plumage in pigeons and their relatives.

i. Let’s imagine that Nadeau et al., tested 5 genes, and got the followingdN/dS ratios:

gene1: 0.01
gene2: 0.05
gene 3: 0.90
gene 4: 1.01
gene 5: 2.34

Which gene has a dN/dS ratio that provides the strongest evidence of negative (‘purifying’) selection?

The correct option is gene 1 with the dN/dS ratio of 0.01

Explanation:

In order for negative selection to occur, the dN/dS ratio has to be between 0 and 1. There three genes that lie within this range, and hence, we can choose the smallest one to provide the strongest evidence among those to represented as the one being negatively selected. Where the dN/dS ratio is equal to 1, it means neutral and where the dN/dS ratio is greater than 1, it means positive selection.

Hope that answers the question, have a great day!

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