4、遗传变异（7）

nullnullHeredity — Variation — genotype Variationphenotype VariationnullMorphological ChangenullBacteriaL form bacteriaP.N.C. LysozymeL form of V. cholerae V. choleraeL Form ChangenullStructure ChangeCapsule Culture mediumLose of capsuleMouseFlagella0.1% carbolic acidlose of FlagellaOHnull Colonial VariationRSnullI. Chromosomeclosed double-Stranded circular DNA molecules 1、多为单拷贝基因 2、功能相关的基因高度集中成操纵子 3、具有连续的基因结构，无内含子 4、不编码的基因较少特点：nullII. Plasmid Plasmids are small， circular/line ，extra-chromosomal ，double-stranded DNA molecules； They are capable of self-replication and contain genes that confer some properties , such as antibiotic resistance ，virulence factors ； They are not essential for cellular survival. nullnullnullTransfer properties Conjugative plasmids； Non－conjugative plasmids Phenotypic effects F factor；Col plasmids；R factor；Vi plasmid Copy Numbers Stringent plasmid；Relaxed plasmids Compatibility Compatibility plasmid；Incompatibility plasmidsClassification of Plasmidsnull--- Virulent phage and Temperate phage III. Bacteriophage (phage)1. Definition--- viruses that infect bacteria, fungi, spirichaete et al.--- being highly host-specific--- obligate intracellular parasites--- being a type of bacterial genetic materialsnull2. Properties of phage1) MorphologyUnit of measurement --- nm ; Visible with EM nullT4 bacteriophage of E. coli null2) StructureHeadTail3) Composition3) CompositionNucleic acid: either DNA or RNA but not both ds DNA, ss RNA, ss DNA encode 3-5 gene products to over 100 gene products Protein: function in infection and protect the nucleic acid null3. Relation between host cell and phage1) Lytic or Virulent PhagesnullAdsorptionnullPenetrationnullBiological SynthesisnullMaturation and ReleasenullLytic cyclenullPlaquePhenomenon of lytic bacterianull2) Lysogenic or Temperate Phage2) Lysogenic or Temperate PhageLysogenic phages are those that can either multiply via the lytic cycle or enter a quiescent state in the cell. In this quiescent state most of the phage genes are not transcribed; the phage genome exists in a repressed state. nullAdsorptionnullPenetrationnullProphage FormationnullLysogenic bacteriumInductionInductionReplicationReplicationnullMaturation and Releasenullnull--- jumping genes or movable genesInsertion sequence, ISTransposon,TnMu phage---IV. Transposable elementnullBeing transposable genetic elements that carry no known genes except those that are required for transposition small stretches of DNA that have at their ends repeated sequences. Between the terminal repeated sequences there are sequences that can control the expression of the genes but no other nonessential genes are present.Insertion sequences (IS)null Being transposable genetic elements that carry one or more other genes in addition to those which are essential for transposition Its structure is similar to IS. The extra genes are located between the terminal repeated sequences. Many antibiotic resistance genes are located on transposons. Since transposons can jump from one DNA molecule to another, these antibiotic resistance transposons are a major factor in the development of multiple drug resistance.Transposons (Tn)null 一种运动性的DNA分子，具有独特结构可捕获和整合外源性基因，使之转化为功能性基因的达单位。可存在于染色体、质粒或转座子上，是细菌固有的遗传单位。 integron -gene cassettes systemV. Integron ( In)null5’3’intIgene2gene1 Structure of InattIABCP1P2PattC5CS 3CSVariable region gene cassettes nullI. Mutation1. Type --- spontaneous mutation and induced mutation --- point mutation and multiple mutationnull2. Mechanism --- substitution (transition and transversion) --- breakage (deletion or insertion) --- rearrangement (inversion or duplication) nullnull1. TransformationCell-free DNA donor recipientAbsorb directly II. Gene transfer and recombinationnullExperiment of transformationnullnullnullnull2. Conjugationdonor recipientSex pili Conjugative PlasmidnullMethod F+ ⅹ F - F+Hfr ⅹ F - F-F’ plasmidR plasmidnull1) F+ ⅹ F - 2F+null2) Hfr ⅹ F - F-null3) F’ ⅹ F - 2F’null4) R Plasmid--- component ofResistance determinantRTF(coding sex pili)null3. Transductiondonor recipientPlasmid, chromosome Temperate phage Generalized transduction Restricted transductionnull1) Generalized transduction nullGeneralized transductionnullGeneralized transductionnullGeneralized transductionnull2) Restricted transduction nullRestricted transduction null4. lysogenic conversionnull5. Protoplast Fusion