Source: Human Male Karyotype image, Public Domain: http://upload.wikimedia.org/wikipedia/commons/5/53/NHGRI_human_male_karyotype.png; Down Syndrome Karyotype image, Public Domain: http://upload.wikimedia.org/wikipedia/commons/1/11/Down_Syndrome_Karyotype.png
When chromosomes don’t separate during meiosis causing gametes to have abnormal numbers, Down syndrome is an example of this.
A genetic disorder in which the 21st pair of chromosomes have three chromosomes vs. the normal pair, this is called a trisomy.
A genetic condition in which an X chromosome is missing, if the child is not miscarried, the effects can range from non-life threatening to life threatening. People with Turner syndrome are female due to the presence of only an X chromosome, are almost universally infertile and typically have cardiovascular issues along with other organ system problems.
A condition in which a person has an XXY chromosomal pattern; males that inherit this are often infertile, may develop breasts and other female secondary characteristics and possible mental retardation.
A condition in which a male inherits an extra Y chromosome; XYY syndrome doesn’t express any cognitive or life threatening abnormalities, it just tends to make males taller than average.