is replaced by a pseudo color in a dedicated image analysis software. thus, chromosomes or chromosome sections can be visualized and identified, allowing for the analysis of chromosomal rearrangements. in the case of spectral karyotyping, image processing software assigns a pseudo color to each spectrally different combination, allowing the visualization of the individually colored chromosomes. spectral human karyotype multicolor fish is used to identify structural chromosome aberrations in cancer cells and other disease conditions when giemsa banding or other techniques are not accurate enough. digital karyotyping digital karyotyping is a technique used to quantify the dna copy number on a genomic scale. short sequences of dna from specific loci all over the genome are isolated and enumerated. this method is also known as virtual karyotyping. using this technique, it is possible to detect small alterations in the human genome, that cannot be detected through methods employing metaphase chromosomes. some loci deletions are known to be related to the development of cancer. such deletions are found through digital karyotyping using the loci associated with cancer development. chromosome abnormalities main article: chromosome abnormalities chromosome abnormalities can be numerical, as in the presence of extra or missing chromosomes, or structural, as in derivative chromosome, translocations, inversions, large-scale deletions or duplications. numerical abnormalities, also known as aneuploidy, often occur as a result of nondisjunction during meiosis in the formation of a gamete; trisomies, in which three copies of a chromosome are present instead of the usual two, are common numerical abnormalities. structural abnormalities often arise from errors in homologous recombination. both types of abnormalities can occur in gametes and therefore will be present in all cells of an affected person's body, or they can occur during mitosis and give rise to a genetic mosaic individual who has some normal and some abnormal cells. in humans chromosomal abnormalities that lead to disease in humans include turner syndrome results from a single x chromosome (45,x or 45,x0). klinefelter syndrome, the most common male chromosomal disease, otherwise known as 47,xxy, is caused by an extra x chromosome. edwards syndrome is caused by trisomy (three copies) of chromosome 18. down syndrome, a common chromosomal disease, is caused by trisomy of chromosome 21. patau syndrome is caused by trisomy of chromosome 13. trisomy 9, believed to be the 4th most common trisomy, has many long lived affected individuals but only in a form other than a full trisomy, such as trisomy 9p syndrome or mosaic trisomy 9. they often function quite well, but tend to have trouble with speech. also documented are trisomy 8 and trisomy 16, although they generally do not survive to birth. some disorders arise from loss of just a piece of one chromosome, including cri du chat (cry of the cat), from a truncated short arm on chromosome 5. the name comes from the babies' distinctive cry, caused by abnormal formation of the larynx. 1p36 deletion syndrome, from the loss of part of the short arm of chromosome 1. angelman syndrome – 50% of cases have a segment of the long arm of chromosome 15 missing; a deletion of the maternal genes, example of imprinting disorder. prader-willi syndrome – 50% of cases have a segment of the long arm of chromosome 15 missing; a deletion of the paternal genes, example of imprinting disorder. chromosomal abnormalities can also occur in cancerous cells of an otherwise genetically normal individual; one well-documented example is the philadelphia chromosome, a translocation mutation commonly associated with chronic myelogenous leukemia and less often with acute lymphoblastic leukemia. history of karyotype studies chromosomes were first observed in plant cells by carl wilhelm von nägeli in 1842. their behavior in animal (salamander) cells was described by walther flemming, the discoverer of mitosis, in 1882. the name was coined by another german anatomist, heinrich von waldeyer in 1888. it is neo-latin from ancient greek κάρυον karyon, "kernel", "seed", or "nucleus", and τύπος typos, "general form") the next stage took place after the development of genetics in the early 20th century, when it was appreciated that chromosomes (that can be observed by karyotype) were the carrier of genes. the term karyotype as defined by the phenotypic appearance of the somatic chromosomes, in contrast to their genic contents was introduced by grigory levitsky who worked with lev delaunay, sergei navashin, and nikolai vavilov. the subsequent history of the concept can be followed in the works of c. d. darlington and michael jd white. investigation into the human karyotype took many years to settle the most basic question: how many chromosomes does a normal diploid human cell contain? in 1912, hans von winiwarter reported 47 chromosomes in spermatogonia and 48 in oogonia, concluding an xx/xo sex determination mechanism. painter in 1922 was not certain whether the diploid of humans was 46 or 48, at first favoring 46, but revised his opinion from 46 to 48, and he correctly insisted on humans having an xx/xy system. considering the techniques of the time, these results were remarkable. fusion of ancestral chromosomes left distinctive remnants of telomeres, and a vestigial centromere joe hin tjio working in albert levan's lab found the chromosome count to be 46 using new techniques available at the time: using cells in tissue culture pretreating cells in a hypotonic solution, which swells them and spreads the chromosomes arresting mitosis in metaphase by a solution of colchicine squashing the preparation on the slide forcing the chromosomes into a single plane cutting up a photomicrograph and arranging the result into an indisputable karyogram. the work took place in 1955, and was published in 1956. the karyotype of humans includes only 46 chromosomes. the other great apes have 48 chromosomes. human chromosome 2 is now known to be a result of an end-to-end fusion of two ancestral ape chromosomes.