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Microbial Genetics. Gene Transfer,Genetic Engineering,and Genomics 1.   Genetic recombination. 2.   Genetic engineering. 3. Microbial genomics. A. Genetic Terminology. Genotype The genetic compliment of an organism Types of genotypic changes Mutation Conjugation Transduction

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Gene Transfer,Genetic Engineering,and Genomics

1.   Genetic recombination.

2.   Genetic engineering.

3. Microbial genomics.

slide4
Genotype
  • The genetic compliment of an organism
  • Types of genotypic changes
    • Mutation
    • Conjugation
    • Transduction
    • Transformation
slide5
Phenotype
  • The genetic expression of an organism
  • Types of phenotypic expressions
    • Morphology
    • Cultural
    • Physiological
slide7
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

slide9
Replication of the chromosome
  • DNA polymerase
  • The semiconservative method
  • Replication of a closed loop chromosome
  • Okazaki fragments
  • Rolling circle method
slide11
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
slide13
Permanent alteration in the DNA

Example: nonpathogenic Yersinia pestis

have genes that cause them to remain in

mid gut, pathogenic Y. pestis do not have

these genes

Types of mutations

Spontaneous

Induced

slide14
Spontaneous mutations

Occurs every 106 to 1010 replications

1 mutation in every billion bacteria

Example: Neisseria gonorrhoeae penicillin resistance original mutation was spontaneous

Example: Salmonella strains antibiotic resistance

slide15
Induced mutations
  • Chemical or Physical agents enhance mutation rate
  • Mutagens
    • Ultraviolet light—mechanism of action
    • Chemicals
    • Chromosomal changes
slide18
Mutation Type

Point (substitution)

(leu) (ser) (arg)

Normal AAT AGT GCC

(leu) (cyst) (arg)

Mutant AAT TGT GCC

slide19
Mutation Type

Frameshift (deletion)

(leu) (ser) (arg)

Normal AAT AGT GCC

(leu) (val)(pro)

Mutant AAT AGTGCCA

slide20
Mutation Type

Frameshift (insertion)

(leu) (ser) (arg)

Normal AAT AGT GCC

(leu) (glut)(cyst)

Mutant AAT CAGTGCC

slide21
Repair Mechanisms

DNA repair enzymes

Many enzymes

Constantly checking for errors

Repair mechanisms

Mismatch repair “proofreads”

Damage repair

Excision repair

Dimer repair (UV light)

slide24
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
slide28
Transformation

Description

Griffith's experiments

Modern interpretation: Avery,McLeod & McCarty

Mechanism

Competence

slide31
Conjugation
  • Male and female cells
  • Role of F factors (plasmids)
  • High frequency of recombination strains
    • Mechanism of Hfr conjugation
  • Sexduction
slide34
Transduction
  • Description
  • Role of the bacteriophage
    • The lytic cycle
    • Lysogeny
  • Generalized transduction
slide39
1. Mechanism proposed by Jacob and Monod
  • 2. The operon theory
  • 3. Repressor-inductor model
slide42

Genetic Engineering

  • Genetic Engineering Was Born from Genetic Recombination
    • Genetic engineering involves changing the genetic material in an organism to alter its traits or products
    • A recombinant DNA molecule contains DNA fragments spliced together from 2 or more organisms
slide43
History of Genetic Engineering

Discovery of endonucleases

Plasmids and sticky ends

slide44
Modern applications
  • Pharmaceutical production
    • Insulin, interferon, hormones, vaccines etc.
  • Genetically engineered plants
  • Animal gene alterations
  • Gene probes
  • DNA fingerprinting
  • The human genome initiative
slide49

Microbial Genomes Have Been Sequenced

    • Hundreds of microbial genomes have been sequenced since the first in 1995
      • Many of which are pathogens
  • Segments of the Human Genome May Have “Microbial Ancestors”
    • As many as 200 of the 35,000 human genes are essentially identical to those of Bacteria
      • They were passed down from early ancestors of humans
slide50

Microbial Genomics Will Advance Our Understanding of the Microbial World

    • Knowing genomes of bacteria that cause food-borne diseases can help us:
      • develop detection methods
      • make food safer
    • It can help us identify microbes that cannot be cultured in the lab
    • Environmental genomics helps us understand how microbial communities function
slide51

Microbial Genomics Will Advance Our Understanding of the Microbial World

    • Environmental genomics can help develop bioremediation techniques
    • Genomics can help develop detection methods for potential bioweapons organisms and other agents of warfare
slide52

Comparative Genomics Brings a New Perspective to

Defining Infectious Diseases

Studying Evolution

  • Types of Genomics
  • Functional genomics attempts to discover:
    • the function of proteins coded for in a genome
    • how the genes interact, allowing the microbe to grow and reproduce
    • Comparative genomics compares the DNA sequence of one microbe to another similar or dissimilar organism