<Li> Squashing the preparation on the slide forcing the chromosomes into a single plane </Li> <Li> Cutting up a photomicrograph and arranging the result into an indisputable karyogram . </Li> <P> The work took place in 1955, and was published in 1956 . The karyotype of humans includes only 46 chromosomes . Rather interestingly, the 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 . </P> <P> The study of karyotypes is made possible by staining . Usually, a suitable dye, such as Giemsa, is applied after cells have been arrested during cell division by a solution of colchicine usually in metaphase or prometaphase when most condensed . In order for the Giemsa stain to adhere correctly, all chromosomal proteins must be digested and removed . For humans, white blood cells are used most frequently because they are easily induced to divide and grow in tissue culture . Sometimes observations may be made on non-dividing (interphase) cells . The sex of an unborn fetus can be determined by observation of interphase cells (see amniotic centesis and Barr body). </P>

How many chromosomes are in a human karyotype