We define karyotype as the set of chromosomes contained in the cells of an organism.
Morphologically, these chromosomes are identified, differentiated and classified according to the size and location of the centromere (region of the chromosome intermediate to the symmetrical or asymmetrical, short or long arms).
Classification of chromosomes:
Metacentric → Centromere positioned at the center of the chromosome; Submetacentric → Centromere displaced to one end of the chromosome; Acrocentric → Chromosome bearing a terminal sphere (satellite), located at the end of the short arm; Telocentric → Chromosome formed by only one arm, with strictly terminal centromere.
In order to determine and visualize the karyotype, making it possible to quantify the typical number of chromosomes of a species, it is necessary to interrupt the cell division process at the time of metaphase, the phase in which the chromosomes reach the maximum condensation.
In the human species, the karyotype of a diploid cell, for example, consists of 46 chromosomes, the last sex-defining pair (XX or XY – allosomal pair), differing the male and female gender (man and woman) and the other 22 pairs (autosomal - AA) responsible for decoding the other characteristics.
Thus, we have for a normal karyotype of the human species, the following possible representations:
Male karyotype → 22AA + XY or 46,XY
A woman's karyotype → 22AA + XX or 46,XX