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T4 �������

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Photograph of phage T2 plaques on a lawn of E. coli

bacteria

T2 phage

T2 mutant phage

T2 r : rapid-lysis mutantT2 r+:wild-type

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3

Phage recombination in cells infected with two different strains of phage T2

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T2 r : rapid-lysis ���

4

The life cycle of a lysogenic bacterial virus

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Insertion of the chromosome of phage

λ into E.colichromosome

6

Insertion of Mu DNA

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Transduction, the passive transfer of genetic material from one bacterium to another by means of carrier

phage particles

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Specialized transducing phage

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9

The demonstration of crossing over with

in the gene

10

The genetic map of the rIIA and rIIB genes of phage T4

��"����'��%� �� ��!#���%������(�$�&��!�����%� ������S. Benzer, PNAS, (1961)

11

Deletion mutations with in the rII region of T4

12

The rII region consists of two

distinct genes that can complement each other during

simultaneous infection

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13

The Genetic Systems Provided by E. coli

Molecular Biology of the Gene

14

Fluctuation analysis of bacterial resistance to phage

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15

Replica plating

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16

Isolation of mutant E. coli cells with a specific growth

factor requirement

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Enriching mutants I

direct selection counterselection

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Enriching mutants II

physical selection

pH-sensitive dyes to detect metabolic mutants

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19

The use of growth factor requirments to demonstrate sexuality in E. coli

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20

The attachment of a male F pilus to

the surface of a femail cell

F pilus

Type-I pili

21

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23

The genetic map of F factor of E. coli

(94 kb)fin : fertility inhibitionphi : phage inhibition

inc : incompatibilityrep : replicationtra : the transfer of the F factor to female cells ilz : immunity to lethal zygosisori : origin of transer replication

Hfr : the positions where insertion elements on F recombine with the bacterial chromosome

24

The transfer of F+ DNAto an F- cell ����

25

Hfr (high frequency of recombination)

Integratiion of the F factor into the main chromosome

Movement of the bacterial chromosome from an Hfr cell into an F- cell

26

Conjugation between F- and Hfr bacteria, as shown in a classic diagram

F. Jacob & E.L. Wollman, Sexality and the Genetics of Bacteria, (1961)

27

The frequency fo donor Hfr marker genesThe relative gene order ⇨ azi-T1-lac-gal

28

Order of genes in conjugal transfer in different Hfr strains

29

Complete genetic map of E. coli I

Flagellar region I

Flagellar region IIIFlagellar region II

30

gal

lacazileuthr

Complete genetic map of E. coli II

31

The genetic maps

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32

4.6Mb 4.2Mb

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