Errors in Meiosis:

1. The normal separation of chromosomes or sister chromatids is termed as disjunction. When the separation is not normal, it is called non-disjunction. This results in the production of gametes which have either more or less than the usual number of chromosomes i.e. there may be trisomy (2n+1) or monosomy (2n-1).
2. It causes several medical conditions in humans such as Down’s syndrome (trisomy of chromosome 21), Klinefelter’s Syndrome (an extra X chromosome in males), Turner’s Syndrome (only one X chromosome present in females). Such individuals have 45 or 47 chromosomes.