Chromosome abnormalities, also known as chromosome dysgenesis, refer to abnormalities in the number and structure of chromosomes. Chromosomes are composed of DNA and proteins, and most genes are located in the DNA of chromosomes. Chromosomes are the basic substances that make up the cell nucleus and are the carriers of genes. Chinese American Jiang Youxing (1956) found that humans have 46 chromosomes, and Caspersson et al. (1970) published the first human chromosome banding photos. Since the Paris International Chromosome Nomenclature Conference in 1971, more than 3,000 abnormalities in the number and structure of human chromosomes have been discovered. More than 100 chromosomal disease syndromes have been confirmed. Mental retardation and growth retardation are common characteristics of chromosomal diseases.