Genomic balance effects on gene expression and the organism

Changes in dosage of individual chromosomes have long been known to have detrimental effects on the phenotype. Molecular analyses have revealed that aneuploidy affects gene expression across the genome with the major effects being direct and inverse correlations with the varied dosage. The inverse effect is typically more prevalent especially in aneuploids with an increased chromosomal dosage. Small heterozygous deletions removing one of the two copies of a gene typically exhibit a gene dosage effect for the included genes, but larger aneuploids exhibit the global modulations. When the inverse effect also operates on the target genes being varied in an aneuploid, dosage compensation results with expression levels similar to the corresponding genomically balanced control. Most substantial aneuploids alter the total transcriptome size but with subsets of genes deviating from the general trend. The greatest reductions in transcriptome size are associated with the most detrimental phenotypic effects on the organism. Aneuploidy effects in the endosperm involve a maternal to zygotic balance or a cumulative effect typical of other tissues. Genomic balance analyses reveal the stoichiometric effects on gene regulation, the trajectory of duplicated genes in evolution, and the eventual consequences for the organism.