ABSTRACT
A basic knowledge of disease inheritance and relevant genetic musculoskeletal disorders is required by the orthopaedic surgeon. Learn to draw a family pedigree of single-gene inheritance and know the gene mutations of the more common conditions. Chromosomes are structures found within the cell nucleus. Chromosomes are composed of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), polysaccharides and histone and non-histone proteins. Chromosomal abnormalities can involve whole chromosomes or result from structural changes of one or more chromosomes. Monosomy, the loss of one chromosome, occurs less often than an increase in number of chromosomes. In trisomy, the cells have an extra chromosome. The addition of an extra X sex chromosome is seen in Kleinfelter's syndrome (XXY). Mucopolysaccharidoses (MPS) are a group of inherited metabolic disorders caused by deficiency of specific lysosomal enzymes, which results in intracellular accumulation of partially degraded glycoaminoglycans. Duchenne's muscular dystrophy (DMD) is the most common form of muscular dystrophy, and is an X-linked recessive myopathy affecting only males.
