The number of chromosomes in normal human body cells is 23 pairs or 46, of which 22 pairs are autosomes, which are common to both males and females. There are also a pair of sex chromosomes, which determine sex, and are different for males and females. Chromosomes are made up of nuclear proteins and are located in the nucleus of the cell. They are the carriers of the genetic material, genes, and can be stained with an alkaline dye to make them visible. Each pair of autosomes is the same in size and shape, with basically similar properties, and its shape and number are characterized by germline. The sex chromosomes are a special pair of chromosomes, called sex chromosomes because the X and Y chromosomes can determine sex; the male sex chromosome is XY, while the female sex chromosome is XX. It is important to note that some diseases are inherited with the genes on the sex chromosomes, and thus clinical features such as male-to-female transmission and female-to-male transmission can occur. When pregnant women with familial hereditary disease factors become pregnant, early clarification of the chromosome type of the fetus can help in the clinical diagnosis of some sex chromosome genetic diseases. Consultation with a specialized doctor is recommended for specific cases.