An Exceptionally Complex Chromosome Rearrangement in the Great Tit (Parus major): Genetic Composition, Meiotic...

Area of Science:

• Genomics
• Evolutionary Biology
• Avian Genetics

Background:

• Chromosomal structural variations, including inversions and copy-number variants (CNVs), are key drivers of genomic and phenotypic diversification in birds.
• These variations influence recombination, gene expression, and overall genome architecture, contributing to adaptation.

Purpose of the Study:

• To characterize a complex structural polymorphism on chromosome 1A in the Siberian great tit (Parus major).
• To investigate the genomic features and potential evolutionary implications of this rearrangement.

Main Methods:

• Cytogenetic analysis
• Genomic approaches (e.g., sequencing and assembly)
• Comparative genomics

Main Results:

• A complex structural polymorphism on chromosome 1A was identified in the Siberian great tit population (19% heterozygote frequency).
• The rearrangement involves a ~55 Mb paracentric inversion and a >30 Mb expansion of the short arm due to amplified genomic loci.
• A region homologous to FAM118A, containing a tandem repeat, is amplified ~20-fold in the rearranged variant, reaching ~50,000 copies.

Conclusions:

• This complex structural polymorphism provides a unique model for studying genome innovation and adaptive diversity driven by structural variations.
• Further functional studies are needed to elucidate the biological effects of the amplified FAM118A region and tandem repeats.