Abandoning the Isochore Theory Can Help Explain Genome Compositional Organization in Fish

Area of Science:

• Genomics
• Comparative Genomics
• Bioinformatics

Background:

• Vertebrate genome nucleotide (AT/GC) composition organization is poorly understood.
• The AT/GC heterogeneity in amniotes versus homogeneity in anamniotes is controversial, with recent exceptions in fish.
• Existing knowledge requires reevaluation due to new data and tools.

Purpose of the Study:

• To reevaluate fish genome composition using updated data and methods.
• To compare previous approaches for assessing genome composition with new in silico analyses.
• To clarify the AT/GC heterogeneity in fish genomes.

Main Methods:

• In silico analysis of fish genomes with minimal user input.
• Comparison of traditional GC% plots with authentic GC% distribution histograms.
• Assessment of the influence of sequence size, chromosome size, and genome size on GC% values.

Main Results:

• Discrepancies found between traditional GC% plots and actual GC% distribution histograms in fish genomes.
• Previous methods distorted GC% values in fish, suggesting homogeneity and AT-richness.
• Sequence size, chromosome, and genome size significantly influence GC% value clustering and analysis results.

Conclusions:

• Traditional methods for assessing fish genome composition are flawed and require revision.
• Fish genomes exhibit AT/GC heterogeneity, challenging the established dichotomy with anamniotes.
• Chromosome size and transposons are potential drivers of AT/GC heterogeneity, more so in mammals than fish.