Detecting natural selection Flashcards
Describe what the null hypothesis is established as in tests for detecting natural selection.
The null hypothesis assumes that the evolutionary rate for the test data is the same as for the neutral data (i.e the reference data that is established to be under neutral evolution). In other words, the tested data is only under the force of genetic drift and not selection.
What is the Hudson-Kreitman Aguade test?
A test for detecting if natural selection is acting on certain genes or sequences in species. It uses both polymorphism data and divergence data. It uses the ratio of the diversity of a gene within a species through the divergence of the gene over time. The ratios of certain genes are compared. If the genes are under neutral evolution, all ratios should roughly be the same. But if they are not the same, we can assume the gene with the divergent ratio is under selection. We can assume this because the rate of fixation of neutral mutations should be constant across loci and species.
Why are non-coding regions often more genetically variable within and between species?
Non-coding regions don’t code for functional protein sequences and are not under the same functional constraint as a coding sequence. protein coding sequences are often under purifying selection because substitutions are often deleterious.
