Molecular exam quesiton 6

Consider two genomic islands within Pseudomonas aeruginosa that were identified by having non-native nucleotide composition; you notice that one island is significantly closer to the native genome composition than the other. explain why these islands have nonnative nucleotide composition using population genetic principles

These genomic islands can have non-native nucleotide compositions because they were likely introduced from another bacterial species through lateral gene transfer. When DNA is transferred from a donor genome into a recipient genome, it initially retains the nucleotide composition of the donor. If the donor and recipient have different mutation rates, their DNA will tend toward different equilibrium nucleotide compositions prior to donation.

Explain how donated genomic island becomes more similar to native nucleotide composition after donating?

Over many generations, mutation pressure gradually changes the nucleotide composition of the transferred DNA towards the recipient genome’s equilibrium composition. This is called mutational amelioration. Since mutation pressure is a relatively weak evolutionary force, the process occurs slowly and the transferred DNA can retain a detectable signature of its original source for a long time

What can we say about the historical origin of non-native nucleotdie composition genomic island in the animal

Their non-native compositions suggest that they originated outside the native genome and were introduced through lateral gene transfer.

What can we say about the timing of the two islands with the one species genome where one is closer to native composition

The island whose composition is closer to the native genome was likely acquired earlier and has had more time to undergo mutational amelioration. Conversely, the island whose composition differs more substantially was likely acquired more recently and has had less time to approach the recipients equilibrium composition. These timing inferences also assume that the islands have experienced similar mutation processes since transfer—differences in their original compositions or subsequent evolutionary histories could also explain the observed differences.