The molecular pathology laboratory of the 21st century

Human cells contain deoxyribonucleic acid in mitochondria and nuclei. Human diseases may be caused by mutations in mitochondrial DNA, nuclear DNA or b oth. The volume of work performed in the diagnostic molecular pathology lab oratory will continue to grow as more disease-related mutations are discove red. Many factors will influence the diagnostic molecular pathology laborat ory in the 21(st) century, such as future clinical laboratory organization, amplification methods, specimen integrity, ethical guidelines and opportun ities to expand service. In the evaluation of a patient suspected of a mito chondrial DNA mutation, care must be exercised in the selection of a primer for amplification and of the specimen to be examined for the mutation. The uneven distribution of normal and abnormal mitochondrial DNA within the va rious tissues (heteroplasmy) may result in a normal mitochondrial DNA seque nce if the wrong tissue is examined. The presence of mitochondrial-like seq uences (pseudogenes) within nuclear DNA may result in amplification of nucl ear genes if generic primers are used to duplicate a mitochondrial DNA gene . Diabetes mellitus is a heterogeneous disease with mutations occurring in a variety of proteins leading to either prereceptor, receptor or postrecept or defects. In this example, the diagnostic molecular pathology laboratory may be asked to define the specific genotype a specific patient with this c ommon phenotype may possess.