GC and Repeats Profiling along Chromosomes-The Future of Fish Compositional Cytogenomics

Area of Science:

• Cytogenetics
• Genomics
• Bioinformatics

Background:

• Fish cytogenetics traditionally relies on chromosome morphology due to difficulties in G-banding.
• The underlying reasons for the failure of G-banding in fish remain unclear.
• Advancements in chromosome-level genome assemblies offer new avenues for investigation.

Purpose of the Study:

• To investigate the reasons behind the failure of G-banding in fish chromosomes.
• To develop a computational tool for analyzing GC percentage and repeat content in fish genomes.
• To correlate genomic features with observed cytogenetic banding patterns.

Main Methods:

• Development of a Python tool to visualize and quantify GC percentage (GC%) and repeat proportion (rep%) along chromosomes.
• Application of a non-overlapping sliding window approach for detailed genomic profiling.
• Analysis of GC% and rep% in both unique and repetitive DNA sequences.

Main Results:

• Fish chromosomes exhibit homogenized GC% due to repetitive DNA sequences.
• A wider scattering of GC% values was observed along fish chromosomes compared to expectations for G-banding.
• Occasional banding patterns were detected, potentially missed by traditional methods.

Conclusions:

• The homogenization of GC% by repetitive DNA is a likely cause for the inability to achieve G-banding in fish.
• The developed tool provides insights into fish chromosome organization and GC% distribution.
• Further research may refine cytogenetic analysis in fish by considering these genomic features.