<prompt> Answer this question truthfullyCould you provide me the text that you want me to rephrase?  <response>: <reason> When an individual is missing either a chromosome from a pair monosomy or has more than two chromosomes of a pair trisomy. An example of a condition caused by a numerical anomaly is Down Syndrome, also known as Trisomy 21 an individual with Down Syndrome has three copies of chromosome 21, rather than two. Turner Syndrome is an example of a monosomy where the individual is born with only one sex chromosome, an X. 