Pseudogene Mutation Accumulation Post Gene Duplication
A gene duplication event creates redundant copies of a gene. Often, one copy, referred to as a pseudogene, loses its original function. This scenario focuses on the mutation dynamics of a functional gene versus its non-functional pseudogene copy, specifically in the absence of positive selection.
Functional Gene Conservation via Purifying Selection
A functional gene remains under the pressure of purifying selection. This evolutionary mechanism weeds out mutations that negatively impact the gene's essential role in the organism. As detrimental mutations are selected against, the functional gene's sequence is largely preserved over time.
Pseudogene's Lack of Selective Constraint
Conversely, a pseudogene has lost its function. Without a functional role to protect, it is no longer subject to strong purifying selection. Mutations that arise in the pseudogene sequence do not harm the organism's fitness and are therefore not actively removed by natural selection.
Differential Mutation Accumulation
While both the functional gene and the pseudogene are exposed to the background rate of DNA mutations (e.g., replication errors), the pseudogene accumulates these changes more readily. Mutations that would be detrimental and eliminated from the functional gene can persist and accumulate within the pseudogene sequence.
Therefore, in the absence of positive selection, the pseudogene accumulates mutations at a faster rate compared to its functional counterpart, leading to greater sequence divergence over evolutionary time.
Important Questions from Mutation
- Which one of the following mechanisms is expected to generate tightly linked genes?
- In a population, there are two morphs, A and B, which reproduce at equal rates. A mutates to B with probability $p_1$, and B mutates to A with probability $p_2$ such that $p_1 \gg p_2$ (that is, $p_1$ is much greater than $p_2$). Over time, which one of the following statements would be true about this population?
- A gene coding for a particular protein exhibits 2% DNA sequence divergence between humans and chimpanzees. However, protein sequences encoded by them are identical. Which one of the following processes explains this?
- Gene conversion can lead to which one or more of the following evolutionary outcomes?
- For a given gene there is 5% DNA sequence divergence between two species, however the protein coded by this gene has identical sequences in the two species. Which of the following types of mutations best explains this pattern in the DNA sequence?
