low; unequal
Repetitive Sequences and Genome Regions
Highly repetitive sequences are commonly found in genomic areas characterized by a low recombination rate.
This association occurs because low recombination frequency limits the disruption and homogenization of repetitive DNA elements, allowing them to accumulate over time.
The primary mechanism responsible for the origin and expansion of these repetitive sequences is unequal crossing over.
During meiosis, unequal crossing over can happen when homologous chromosomes misalign at repetitive DNA segments. This misalignment leads to an uneven exchange, potentially resulting in the duplication of repeat units on one chromosome and their deletion on the other.
Consequently, the combination of a low recombination rate and the occurrence of unequal crossing over explains the prevalence of highly repetitive sequences in specific genome regions.
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?
