Gene conversion is a process where genetic material is exchanged between similar DNA sequences, often non-allelic homologous sequences like those in gene families. This process can lead to specific evolutionary outcomes:
Gene Conversion Evolutionary Outcomes
1. Concerted Evolution
Gene conversion helps maintain sequence identity among members of a multigene family. By regularly "copying" sequences from one member to another, it prevents individual members from diverging significantly. This leads to the genes evolving in a coordinated manner, known as concerted evolution.
2. Increased Expression
Gene conversion can influence a gene's expression level. If conversion occurs between a highly active gene copy and a less active one, or involves the transfer of enhancer or promoter elements, the resulting gene sequence might exhibit increased expression.
3. Increased Sequence Similarity
The fundamental mechanism of gene conversion involves replacing a segment of DNA with a copy from a homologous sequence. This directly results in the two sequences becoming more alike, thus leading to increased sequence similarity between them.
Why Increased Sequence Divergence is Incorrect
Gene conversion promotes uniformity by homogenizing sequences. It replaces variants rather than allowing them to accumulate independently. Therefore, it typically leads to decreased, not increased, sequence divergence between the homologous regions involved.
Based on these points, the evolutionary outcomes of gene conversion include Concerted evolution, Increased expression, and Increased sequence similarity.
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?
- 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?
- Following a gene duplication event, the duplicated copy often loses function and is called a pseudogene. In the absence of positive selection, which of the following is true about these genes?
