allelic imbalance
Deviation from the expected 50:50 ratio of maternal and paternal alleles, indicating copy number alterations or loss of heterozygosity in tumor tissue.
Full Definition
Allelic imbalance refers to the skewed representation of maternal versus paternal chromosome copies in tumor cells, departing from the normal balanced state observed in diploid tissues. This imbalance can result from various mechanisms including chromosomal deletions, amplifications, or copy-neutral loss of heterozygosity events. In cancer genomics analysis, allelic imbalance is detected by comparing the relative abundance of heterozygous SNPs between tumor and normal tissues. The degree and pattern of allelic imbalance provide insights into chromosomal instability, tumor suppressor gene inactivation mechanisms, and overall genomic integrity. Quantitative assessment typically involves calculating the deviation from expected 1:1 allelic ratios across chromosomal regions.
Usage
Usage note: Distinguish from simple LOH; can indicate various chromosomal alterations.
In Context
- "Significant allelic imbalance on chromosome 17q suggested loss of heterozygosity at the BRCA1 locus." — Genomic instability assessment
- "The tumor showed widespread allelic imbalance consistent with chromosomal instability." — Molecular cytogenetics report