Diagnosis at the bedside by gene analysis.

Four different ideas are important in understanding the diagnostic applications of DNA analysis. When DNA changes in a gene are detected, one must determine whether they represent DNA polymorphisms (changes not associated with disease) or mutations that affect expression of the gene. Differences seen in mutations in different patients (heterogeneity) often explain clinical variation at a molecular level. Current methods used for gene analysis include restriction enzyme analysis, polymerase chain reaction amplification, allele-specific oligonucleotides, denaturing gradient gels, and DNA sequence analysis. Gene diagnosis is applicable to many clinical disorders, both genetic and acquired. Requisites are a portion of the gene involved or a segment of DNA that lies close to the gene.