Down syndrome is caused by an error in meiosis resulting in and extra chromosome 21 to be in a gamete. During meiosis l the homologous chromosomes don’t separate during anaphase. During anaphase ll the sister chromatids don’t separate in meiosis ll. When this gamete with 24 chromosomes fuses with another gamete with 23 chromosomes it makes a zygote with 47 chromosomes, resulting in the offspring to have down syndrome. Most people with Down syndrome have physical characteristics that look different from normal people. They have upward slanting eyes, low muscle tone, small stature and a short neck, a flat nose, and a protruding tongue. Most people with Down syndrome have poor cognitive features with mild to moderate mental disabilities. They also have an increased risk to congenital heart defects, respitory or hearing problems, Alzheimer’s disease, childhood leukemia, epilepsy and thyroid conditions. Although they do have a lower risk of some types of cancers, diabetes, and hardening of the arteries. Approximately 1 in 750 babies are born with Down syndrome. Women under 30 have a 1 in 1000 chance of having a baby with Down syndrome while women who are 50 will have a 1 in 10 chance. The older the women gets the more often dis-conjunction happens while producing gametes.
