Medical Microbiology

178 3 GeneralBacteriology

strictionendonucleasescandestroyforeignDNAthatbearsno“fingerprint”

(modification)signifying“self.”Thesemodificationstaketheformofmethy-

lationoftheDNAbasesbymodificationenzymes.

Bacterialrestrictionendonucleasesareinvaluabletoolsinmoderngene

cloningtechniques.Theprocessistermedgene“cloning”becauseitinvolves

replicationofDNAthathasbeenmanipulatedinvitroinasuitablehostcellso

astoproduceidenticalcopiesofthisDNA:molecularclonesorgeneclones.

DNACloning

Fig.3. 24 TheDNAsequence

tobeclonedisintegratedina

vector DNA(plasmid, bacte-

riophagegenome).Thisvector

isthentransferredintoahost

bacterium,e.g.,E.coli,foriden-

ticalreplication.

3

Kayser, Medical Microbiology © 2005 Thieme