A karyotype may be prepared from chorionic villi cells of the foetus. HLA is a multiple allelic system. The inheritance of HLA alleles follow a codominant Mendelian system. The HLA proteins are found inside the cell. HLA B37 is associated with ankylosing spondylitis.
Turner syndrome is seen only in females.
In classical haemophilia A, carriers may show clinical features. In Duchenne muscular dystrophy, carriers never produces affected males, if the husband is normal. Carrier states are seen in achondroplasia. Certain carrier states can be detected using DNA studies. Fragile X syndrome.