Cytogenetics: a branch of genetics that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis. Changes that affect the number and/or structure of the chromosomes can cause problems with growth, development, and how the body functions. Changes to chromosome structure can disrupt genes, causing the proteins made from disrupted genes to be missing or faulty. The analysis of chromosomes in human development and disease is accomplished through classical cytogenetic procedures (such as G-banding) combined with advanced molecular techniques such as genomic microarray analysis.