In a normal situation, all the cells in an individual will have<unk>  chromosomes with one being an<unk>  and one a Y or with two<unk> s. However, sometimes during this complicated early copying process (DNA replication and cell division), one chromosome can be lost. In<unk> ,X/46,XY, most or all of the Y chromosome is lost in one of the newly created cells. All the cells then made from this cell will lack the Y chromosome. All the cells created from the cells that have not lost the Y chromosome will be<unk> Y. The<unk> ,XY cells will continue to multiply at the same time as the<unk> ,X cells multiply. The embryo, then the fetus and then the baby will have what is called a<unk> ,X/46,XY constitution. This is called a mosaic karyotype because, like tiles in mosaic floors or walls, there is more than one type of cell. There are many chromosomal variations that cause the<unk> ,X/46,XY karyotype, including malformation (isodicentricism) of the Y chromosomes, deletions of Y chromosome or translocations of Y chromosome segments. These rearrangements of the Y chromosome can lead to partial expression of the SRY gene which may lead to abnormal genitals and testosterone levels.
45,X/46,XY mosaicism
XY gonadal dysgenesis
XX gonadal dysgenesis
Y chromosome microdeletion
Distal trisomy 10q
Small supernumerary marker chromosome
XY sex-determination system
Tetrasomy 18p