Segmental duplication

Definition

Segmental duplication refers to the phenomenon where large regions of the genome are copied and duplicated, resulting in identical or nearly identical sequences of DNA. These duplications play a significant role in genome evolution by contributing to genetic diversity, gene family expansion, and the potential for evolutionary innovation through new gene functions.

5 Must Know Facts For Your Next Test

1. Segmental duplications can cover regions ranging from a few hundred base pairs to several megabases in size.
2. These duplications are important for evolutionary processes as they can lead to the creation of gene families, allowing for functional diversification of proteins.
3. Segmental duplications are often associated with genomic instability, which can contribute to diseases such as cancer.
4. They can arise through mechanisms such as non-allelic homologous recombination during meiosis.
5. The presence of segmental duplications is particularly pronounced in certain species, such as humans and some primates, influencing their evolutionary trajectories.

Review Questions

• How do segmental duplications contribute to the evolution of gene families?
  • Segmental duplications play a crucial role in the evolution of gene families by providing additional copies of genes that can accumulate mutations over time. This process allows for the diversification of gene functions; some duplicates may retain the original function while others may evolve new roles or become non-functional. As a result, segmental duplications expand genetic diversity within a population and provide a substrate for natural selection to act upon.
• What mechanisms lead to segmental duplications, and how can they affect genomic stability?
  • Segmental duplications primarily arise through non-allelic homologous recombination during meiosis, where misalignment of homologous chromosomes leads to unequal crossing over. This process can result in duplications of DNA segments. While these duplications can foster genetic diversity and innovation, they also pose risks to genomic stability by creating potential hotspots for further rearrangements or mutations, which can contribute to various diseases including cancer.
• Evaluate the significance of segmental duplications in understanding human evolutionary history and disease susceptibility.
  • Segmental duplications are significant for understanding human evolutionary history as they highlight events where large segments of DNA were duplicated, leading to increased genetic variation. This variation is essential for adaptation and survival in changing environments. Additionally, segmental duplications can influence disease susceptibility; certain duplications have been linked to complex traits and disorders by disrupting normal gene function or creating new genetic pathways. Analyzing these duplications provides insights into both our evolutionary past and current health challenges.

Related terms

copy number variation: A type of genetic variation where sections of the genome are repeated, and the number of copies of those segments can vary between individuals.

genomic rearrangement: Changes in the structure of the genome, including duplications, deletions, inversions, and translocations, that can lead to genetic diversity.

evolutionary innovation: The process by which new functions or traits arise in organisms, often facilitated by mechanisms like segmental duplication that provide raw material for natural selection.