Medical Microbiology

TheGeneticVariabilityofBacteria 179

The techniquesimplifies thereplication ofDNA,makingexperimental

manipulationseasier.Ontheotherhand,thebacteriacanalsobeusedto

synthesizegeneproductsoftheforeigngenes.Suchforeignproteinsare

calledrecombinantproteins.Bacterialplasmidsoftenfunctionintherole

ofvectorsintowhichthesequencestobeclonedareinserted.Fig.3. 24 illus-

tratestheprincipleofgenecloninginsimplifiedform.

Table3. 3 liststhemostimportanttermsusedinthefieldofbacterial

genetics.

Table3. 3 GlossaryofImportantTerminologyinBacterialGenetics

Anticodon TripletsequencesoftransferRNAcomplementarytotheco-

donsofmRNA

Chromosome Seenucleoid

Cistron Geneticunit,identicalto“gene”

Code KeyrelatingtheDNAnucleotide(n=3)sequencetothe

polypeptideaminoacidsequence

Codon Sequenceofthreenucleotides,triplet

Corepressor Seeeffectormolecules

Deletion LossofaDNAsequenceinareplicon

Effectormolecules Smallmoleculesthatinactivate(=inductor)oractivate

(=corepressor)aregulatorproteinbymeansofanallosteric

effect

Episome Historicalterm;characterizesareplicon(e.g.,Fplasmid)oc-

curringeitherinthecytoplasmorintegratedinthebacterial

chromosome

Ffactor Prototypeofaconjugativeplasmid(fertilityfactor)

Gene DNAsegmentcontainingtheinformationusedinsynthesis

ofapolypeptideorRNA

Genome Allofthegeneticinformationcontainedinacell

Genotype Thetotalityofgeneticallydeterminedcharacteristics

Hfrcells ColibacteriawithFfactorintegratedintotheirchromo-

somes,thereforecapableoftransferringchromosomalgenes

atahighfrequencybymeansofconjugation(Hfr=high

frequencyofrecombination)

Inductor Seeeffectormolecules

Integron Geneticstructurecontainingthedeterminantsforasite-

specificrecombinationsystem;responsibleforintegrationor

excisionofmobilegenecassettes

3

Kayser, Medical Microbiology © 2005 Thieme