bacterial genetics

Dr. Rashad Shawgi BabikerM.Sc. (Microbiology)

(UMST)M.Sc. Stud. (Immunology )Institute of Tropical Medicine.

(SAS)

Microbial Genetics

Basic Molecular GeneticsCentral DogmaGene Expression

Genetic VariabilityMutationsRecombinationPlasmids

Genetic EngineeringTerminology and TechnologyProducts and Benefits

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Introduction

DNA is arranged as a single molecule with no histones present, and with no dominance or recessiveness in the genes.

Bacterial chromosome is located in the nucleoid.

In E. coli there are 4000 genes spread over 1.5mm of DNA in less than 1 micrometer of space

Loop domain structure allows for compaction of DNA

F. Control of protein synthesis

Microbial Genetics Basic Molecular Genetics

Central Dogma

Genotype and Phenotype

Genetic Variability-Mutations -Recombinations: Transformation, Conjugation, Transduction

-Plasmids: Conjugative, Resistance, Toxigenic, Metabolic

Genetic Engineering

Terminology and Technology

Products & Benefits of Genetic Engineering12

Mutations

Types of mutations

SpontaneousInduced

Spontaneous mutations

1 mutation in every billion

bacteria

Example: Neisseria gonorrhoeae

penicillin resistance original

mutation was spontaneous

Induced mutations

Chemical or Physical agents

enhance mutation rate

Mutagens

Ultraviolet light—mechanism

of action

Chemicals

Mutation Type

Point (substitution) (leu) (ser) (arg)

Normal AAT AGT GCC

(leu) (cyst) (arg)

Mutant AAT TGT GCC

Mutation Type

Frameshift (deletion) (leu) (ser) (arg)

Normal AAT AGT GCC

(leu) (val) (pro)

Mutant AAT AGT GCC A

Mutation Type

Frameshift (insertion) (leu) (ser) (arg)

Normal AAT AGT GCC

(leu) (glut) (cyst)

Mutant AAT CAGT GCC

Repair Mechanisms

DNA repair enzymesMany enzymesConstantly checking for errors

Repair mechanismsMismatch repair “proofreads”Damage repair

Excision repairDimer repair (UV light)

Mismatch Repair

Excision Repair

Transformation

Conjugation

Male and female cells

Role of F factors (plasmids)

High frequency of

recombination strains

Mechanism of Hfr conjugation

Sexduction

Simple Conjugation

Hfr Conjugation

Transduction

Role of the bacteriophage

The lytic cycle

Lysogeny

Generalized transduction

Lysogeny

Plasmids

Fragments of DNA in the cytoplasm

R Factors - confer drug resistance

Bacteriocins -proteins toxic to other

bacteria and human cell

Many plasmids are found in Gram-

Negative bacteria

Microbial Genetics

Basic Molecular Genetics Central Dogma

Gene Expression Genetic Variability

Mutations, Recombinations, Plasmids

Genetic Engineering-Terminology: Genetic engineering, Gene cloning,

Recombinant DNA technology, Restriction endonucleases, Vectors

-Products of Genetic Engineering: Proteins, Genetically modified organisms, Genes therapy

-Process of Genetic Engineering: Gene cloning, Gene characterization, Gene expression 32

Transposable genetic elementsInsertion sequences

Small DNA segments Provide no genetic informationLocated at several places on the chromosome

TransposonsLarger than Insertion sequencesProvide information for protein synthesis

Sections A & B repeating but reversed “palindrome”

The ‘Benefits’ of Genetic EngineeringGenetically engineered proteins:

Hormones (e.g.interferons, erythropoietin, insulin, growth factors), Vaccines (e.g.Hep B), others

Genetically modified organisms:

Genetically modified foods,

herbicide and pesticide resistant plants

Genetically engineered genes:

Genes for therapy

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