First, you introduce to the parents the importance of karyotype test, by describing its ability to detect two broad categories of abnormalities in chromosomes, (1) and (2). You provide a few examples of genetic disorders that can be caused by chromosomal abnormalities, such as (3) and (4). Some parents would like to know what is the main cause of these genetic disorders. Without going into too much detail, you explain to them that chromosomal abnormalities are usually caused by (5) in meiosis I and meiosis II, when the homologous chromosomes or sister chromatids fail to separate during meiotic cell division.