A karyotype is a picture of the chromosomes in a cell. A karyotype is used to see what kinds of chromosomes a person has. It is created by taking a blood or tissue sample from a person, and then staining the chromosomes with dye and photographing them through a microscope. The photograph is then cut up and rearranged so that the chromosomes are lined up into corresponding pairs. The result is usually reported as the number and type of a person’s chromosomes, such as 45,X (the individual has 22 pairs of matched chromosomes and one X chromosome); 46,XX (the individual has 22 pairs of matched chromosomes and two X chromosomes; 46,XY (the individual has 22 pairs of matched chromosomes), one X chromosome and one Y chromosome); 47, XXY, etc.

Klinefelter Syndrome (47,XXY or XXY syndrome) occurs when an individual has at least two X chromosomes and at least one Y chromosome. It typically results in small testes and reduced fertility.