Directional mutation pressure, mutator mutations, and dynamics of molecular evolution

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genetics

Background:

• The G+C content of DNA varies widely across organisms.
• Understanding mutation biases and their evolutionary consequences is crucial.
• Selective constraints play a role in shaping DNA composition.

Purpose of the Study:

• To analyze the effect of mutator gene mutations on DNA G+C content and evolutionary changes.
• To test predictions of the directional mutation theory under varying selective constraints.
• To challenge established assumptions in molecular evolution.

Main Methods:

• Utilizing a general form of the directional mutation theory.
• Analyzing mutation frequency and cumulative mutations.
• Investigating DNA base composition and nucleotide pair biases.

Main Results:

• Mutator gene mutations can lead to significant shifts in DNA G+C content.
• Mutation frequency per gene is predicted to be lower after equilibrium with neutral DNA bases.
• Explains variation in G+C content among unicellular organisms and intragenomic heterogeneity in eukaryotes.

Conclusions:

• The study's predictions contradict several common assumptions in molecular evolution.
• Challenges the belief in constant evolutionary rates and symmetric phylogenetic trees.
• Questions the generality of higher mutation rates for neutral nucleotides and the deleterious nature of mutator mutations.