DNA mapping in growth and developmental disorders.
DNA mapping techniques are being increasingly applied to familial and acquired disorders affecting growth and development. To understand the potential applications of these techniques, one must first have a good understanding of the components and basic structure of DNA, the genetic code, the basic structure of genes and the roles that various components of gene structure play in regulating gene expression. Following review of this basic information, a variety of DNA mapping techniques including in situ hybridization, Southern blotting, polymerase chain reaction amplification, DNA sequencing and linkage analysis will be covered. Applications of these techniques can enable mapping of unknown genes by detection of loss of allelic heterozygosity or use of linkage analysis and genetic maps. With increasing ease, mutations such as deletions, expansions, rearrangements and point mutations can be detected in diseases such as congenital adrenal hyperplasia, cystic fibrosis, diabetes insipidus, growth hormone deficiency, fragile X syndrome, Laron dwarfism and Turner syndrome. From this discussion, a better understanding of methods of gene localization, uses of genetic maps and rapid, convenient methods to detect a variety of molecular derangements causing familial disorders affecting growth and development will be gained.