THEIMPACTOFMOLECULARGENETICS ON ORALHEALTHPARADIGMS

Asaresult ofourincreased understanding ofthehumangenome, andthefunctional interrelationships ofgene products witheachother andwiththeenvironment, itisbecoming increasingly evident that manyhumandiseases areinflu- enced byheritable alterations inthestructure orfunction ofgenes. Significant advances inresearch methods andnewly emerging partnerships between private andpublic sector interests arecreating newpossibilities forutilization ofgenetic information for thediagnosis andtreatment ofhumandiseases. Theavailability andapplication ofgenetic information totheunderstanding ofnormal andabnormal humangrowth anddevelopment arefundamentally changing thewayweapproach thestudy ofhuman diseases. Asaresult, theissues andprinciples ofmedical genetics arecoming tobear across alldisciplines ofhealth care. In this review, wediscuss someofthepotential applications ofhumanmolecular genetics forthediagnosis andtreatment oforal diseases. Thisdiscussion ispresented inthecontext oftheongoing technological advances andconceptual changes that are occurring inthefield ofmedical genetics. Torealize thepromise ofthis newmolecular genetics, wemustbeprepared tofore- seethepossibilities andtoincorporate these newly emergent technologies intotheevolving discipline ofdentistry. Byusing examples ofhumanconditions, weillustrate thebroad application ofthis emerging technology tothestudy ofsimple aswell ascomplex genetic diseases. Throughout this paper, wewill usethefollowing terminology: Penetrance Inapopulation, defined astheproportion ofindividuals posessing adisease-causing genotype whoexpress thedisease phenotype. Whenthis pro- portion isless than100%, thedisease issaid tohavereduced orincomplete penetrance. Polymerase chain reaction (PCR)-A tech- nique foramplifying alarge number ofcopies ofaspecific DNAsequence flanked bytwooligonucleotide primers. TheDNAis alternately heated andcooled inthepresence ofDNApolymerase andfree nucleotides, sothat thespecified DNAsegment is denatured, hybridized withprimers, andextended byDNApolymerase. MIM-Mendelian Inheritance inMancatalogue number fromV.McKusick's Mendelian Inheritance inman(OMIM, 1998).