Dr. Rashad Shawgi Babiker M.Sc. (Microbiology) (UMST) M.Sc. Stud. (Immunology ) Institute of Tropical Medicine.(SAS)

Microbial Genetics  Basic Molecular Genetics Central Dogma Gene Expression  Genetic Variability Mutations Recombination Plasmids  Genetic Engineering Terminology and Technology Products and Benefits 2

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

DNA Structure

Transcription & Translation

Transfer RNA

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 Engineering 12

Mutations Types of mutations Spontaneous Induced

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 enzymes Many enzymes Constantly checking for errors Repair mechanisms Mismatch repair “proofreads” Damage repair Excision repair Dimer 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 elements Insertion sequences Small DNA segments Provide no genetic information Located at several places on the chromosome Transposons Larger than Insertion sequences Provide information for protein synthesis

Sections A & B repeating but reversed “palindrome”

Genetic Engineering Technology

The ‘Benefits’ of Genetic Engineering  Genetically 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 37