A karyotype is the complete set of all chromosomes of a cell of
any living organism. The chromosomes are arranged and displayed
(often on a photo) in a standard format: in pairs, ordered by
size. Karyotypes are examined in searches for chromosomal
aberrations, and may be used to determine other macroscopically
visible aspects of an individual's genotype, such as sex (XX vs.
XY pair). The study of karyotypes is known as karyology. Normal
human karyotypes are denoted 46,XX (for most women) and 46,XY
(for most men). However, some individuals have other karyotypes
with added or missing sex chromosomes, including 47,XYY, 47,XXY,
47,XXX and 45,X. The other possibility, 45,Y, does not occur, as
an embryo without an X chromosome is incapable of survival. In
the "classic" (depicted) karyotype, a dye, often Giemsa, is used
to make bands on the chromosomes visible. This is also referred
to as G-banding. Each chromosome has a characteristic banding
patern which helps to identify them (notice that the two
chromosomes of o