Cause 2: Problems with DNA replication
Mutations can occur due to the failure of homologous chromosomes or sister chromatids to separate properly during cell division. This includes:
- the failure of a pair of homologous chromosomes to separate in meiosis I
- the failure of sister chromatids to separate during meiosis II
- the failure of sister chromatids to separate during mitosis
Nondisjunction results in daughter cells with abnormal chromosome numbers (known as aneuploidy).
You are expected to be able to identify ploidy changes from karyotypes.
Trisomy 21 (Down Syndrome)
Trisomy 13 (Patau Syndrome)
Trisomy 18 (Edward’s Syndrome)
XXY male (Klinefelter’s Syndrome)
XYY male (XYY Syndrome)
Trisomy X (XXX female)
Monosomy X (Turner’s syndrome)