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The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms. This number, along with the visual appearance of the chromosome, is known as the karyotype , [ 1 ] [ 2 ] [ 3 ] and can be found by looking at the chromosomes through a microscope .
In systems with two sex chromosomes, they can be heteromorphic or homomorphic. Homomorphic sex chromosomes are almost identical in size and gene content. The two familiar kinds of sex chromosome pairs (XY and ZW) are heteromorphic. Homomorphic sex chromosomes exist among pufferfish, ratite birds, pythons, and European tree frogs.
Most spiders have a variation of the XO system in which males have two different X chromosomes (X 1 X 2 O), while females have a pair of X 1 chromosomes and a pair of X 2 chromosomes (X 1 X 1 X 2 X 2). [1] Some spiders have more complex systems involving as many as 13 different X chromosomes. [1] Some Drosophila species have XO males. [10]
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
Offspring have two sex chromosomes: an offspring with two X chromosomes (XX) will develop female characteristics, and an offspring with an X and a Y chromosome (XY) will develop male characteristics, except in various exceptions such as individuals with Swyer syndrome, that have XY chromosomes and a female phenotype, and de la Chapelle Syndrome ...
In those species, there is one sex chromosome, Z. Males have two Z chromosomes, whereas females have one Z. Males are ZZ, while females are ZO. [1] [2] [3] The ancestor of Lepidoptera and Trichoptera had ZO sex determination, which became a ZW sex-determination system in the largest clade, Ditrysia, as well as in Tischerioidea. Some of the ZW ...
Sex chromosomes (also referred to as allosomes, heterotypical chromosome, gonosomes, heterochromosomes, [1] [2] or idiochromosomes [1]) are chromosomes that carry the genes that determine the sex of an individual. The human sex chromosomes are a typical pair of mammal allosomes. They differ from autosomes in form, size, and behavior.
Males with Klinefelter syndrome typically have one extra copy of the X chromosome in each cell, for a total of two X chromosomes and one Y chromosome (47,XXY). It is less common for affected males to have two or three extra X chromosomes (48,XXXY or 49,XXXXY) or extra copies of both the X and Y chromosomes (48,XXYY) in each cell.