Definition
The number of copies of a specific DNA sequence or chromosome present in a cell.
Related Claims
- Protein levels correlate with chromosomal position in aneuploid strains
- Copy number variations account for substantial but secondary gene expression variation
- Single-cell sequencing reveals karyotype heterogeneity in lymphomas
- AneuFinder enables automated quantification of copy number heterogeneity
- Mps1 truncation-induced CIN generates convergent recurrent chromosome gains
- scWGS platform detects copy number variants via shallow sequencing
- Bulk sequencing masks intratumoral copy number heterogeneity
Synthesis
Copy number, defined as the number of copies of a specific DNA sequence or chromosome present in a cell, serves as both a source of genetic variation and a determinant of cellular phenotype through direct effects on gene dosage and protein abundance. Across multiple experimental systems, a clear mechanistic relationship has been established: changes in chromosomal copy number lead to proportional changes in gene expression and protein abundance, with proteins encoded on duplicated chromosomes increasing approximately twofold in aneuploid yeast strains, thereby demonstrating high stoichiometric fidelity between genomic content and proteome composition. Copy number variations contribute substantially to gene expression architecture, accounting for approximately 18% of detectable genetic variation, though this represents a secondary contribution compared to single nucleotide polymorphisms. However, the role of copy number alterations in cancer biology reveals unresolved complexity, as bulk sequencing approaches that measure average DNA content across millions of cells mask extensive intratumoral heterogeneity in chromosome numbers, and single-cell sequencing reveals ongoing chromosomal instability that generates cell-to-cell karyotype variation even within tumors that display recurrent clonal copy number gains, leaving open questions about how selection pressures balance the generation of karyotypic diversity against convergence toward favorable chromosomal states.