Chromosomal Numerical Aberrations

Abstract

Numerical aberrations (whole chromosomal aneuploidy) represent a significant proportion of chromosomal changes found in humans. These aberrations can occur as a consequence of chromosome segregation defects during cell division. Segregation errors that arise during reductive cell division, or meiosis, are upon fertilisation and subsequent embryo development constitutively present in all cells, resulting in whole organismal aneuploidy. Missegregation in mitosis leads to a mosaic distribution of aneuploidy in somatic cells. Aneuploidy is associated with pathological states in most organisms. Numerical aberrations represent a significant cause of pregnancy loss as well as abnormalities found in live births. Moreover, numerical aberrations are frequently found in ageing tissues or in tumour cells. Although the association of aneuploidy and cancer is known for almost a century, the dispute whether this is a cause or a consequence of cell transformation is still ongoing. Recently, new evidence is emerging that numerical aberrations significantly alter the physiology of eukaryotic cells and might indeed directly contribute to tumourigenesis. Key Concepts Numerical chromosomal aberrations result from errors in chromosome segregations. Trisomy, monosomy and polyploidy are among the major causes of spontaneous human abortions. Trisomies compatible with survival often result in multiple defects. Numerical chromosomal aberrations significantly alter physiology of eukaryotic cells. Numerical chromosomal aberrations are frequently found in cancer cells and can contribute to tumourigenesis.