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Replication orientation affects the rate and direction of bacterial gene evolution
1Department of Molecular and Medical Genetics, University of Toronto, 1 King's College Circle, Toronto, Canada, M5S 1A8. e.tillier@utoronto.ca
Journal of Molecular Evolution
|November 18, 2000
Summary
Bacterial DNA replication causes strand-specific base composition biases, known as skews. Genes switching strands adopt the new strand
Area of Science:
- Genomics
- Molecular Biology
- Evolutionary Biology
Background:
- Bacterial genomes exhibit distinct base composition skews between leading and lagging DNA strands.
- These skews, such as an excess of guanosine on the leading strand, are a common genomic feature.
Purpose of the Study:
- To investigate how gene orientation changes affect base composition skews in bacterial genomes.
- To understand the evolutionary implications of replication-driven base composition biases.
Main Methods:
- Analysis of Chlamydia genomes to identify genes that have switched orientation relative to replication direction.
- Comparison of base composition skews in genes before and after orientation switching.
Main Results:
- Genes that invert their orientation relative to DNA replication acquire the base composition skew of their new host strand.
- This phenomenon demonstrates a directional evolutionary force impacting gene sequences predictably.
- Replication-associated skews lead to increased divergence in both DNA and amino acid sequences of switched genes.
Conclusions:
- Gene orientation relative to replication is a significant factor shaping bacterial genome composition.
- Replication-driven skews represent a predictable evolutionary mechanism, unlike many other evolutionary processes.
- Understanding these skews provides insights into genome evolution and sequence divergence in bacteria.