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Microbial Genetics

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Title: Microbial Genetics Author: SMCCCD Last modified by: Nickolas V. Kapp Created Date: 3/25/2003 1:38:47 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: Microbial Genetics


1
Microbial Genetics
  • The how and why of information flow in living
    things.
  • What exactly is living?

2
Genetics Terms
  • Genome
  • Chromosome
  • Gene
  • Base pair
  • Genetic code
  • Genotype
  • Phenotype

3
The Polymers of life
  • Define Polymer
  • Define Monomer
  • What are the polymers of life?
  • Why use polymers?

4
Determine Relatedness
Clinical Focus, p. 223
5
Determine Relatedness
  • Which strain is more closely related to the
    Uganda strain?

Strain Similar to Uganda
Kenya 71
U.S. 51
6
The genetic Code
  • Name the monomers that make up the genetic code.
  • Name the monomers that make up Proteins

7
What is the flow of genetic information in the
bacterial cell?
Verb Enzyme Substrate Product



8
Genetic Map of the Chromosome of E. coli
Figure 8.1b
9
The Flow of Genetic Information
Figure 8.2
10
DNA Replication
  • The double strand of DNA is separated.
  • DNA polymerase reads the DNA strand and creates
    another.
  • The newly synthesized DNA contains an old strand
    and a new strand.
  • The two new strands are then separated into the
    two new daughter cells.

11
Semiconservative Replication
Figure 8.3a
12
DNA Synthesis
Figure 8.4
13
DNA Synthesis
  • DNA is copied by DNA polymerase
  • In the 5' ? 3' direction
  • Initiated by an RNA primer
  • Leading strand is synthesized continuously
  • Lagging strand is synthesized discontinuously
  • Okazaki fragments
  • RNA primers are removed and Okazaki fragments
    joined by a DNA polymerase and DNA ligase

14
Transcription
  • A sequence of DNA is relaxed and opened up.
  • RNA polymerase synthesizes a strand of RNA
  • RNA uses ACGU
  • Starting point is a promoter

15
Transcription
Figure 8.7
16
The Process of Transcription
Figure 8.7
17
Translation
  • mRNA associates with ribosome's (rRNA and
    protein)
  • 3-base segments of mRNA specify amino acids and
    are called codons.
  • Genetic code relationship among nucleotide
    sequence and corresponding DNA sequence.

18
Degenerate Most amino acids are code for by
more than one codon.
  • 64 codons
  • 3 are nonsense
  • Start codon Aug is for methionine.
  • See the codon sequence.

19
The Genetic Code
Figure 8.8
20
Simultaneous Transcription Translation
Figure 8.10
21
The Process of Translation
Figure 8.9
22
The Process of Translation
Figure 8.9
23
The Process of Translation
Figure 8.9
24
The Process of Translation
Figure 8.9
25
The Process of Translation
Figure 8.9
26
The Process of Translation
Figure 8.9
27
The Process of Translation
Figure 8.9
28
The Process of Translation
Figure 8.9
29
Info
  • From information storage to reality.
  • What determines what info is used
  • What determines how information is moved about.

30
Regulation
  • Constitutive genes are expressed at a fixed rate
  • Other genes are expressed only as needed
  • Repressible genes
  • Inducible genes
  • Catabolite repression

31
Operon
ANIMATION Operons Overview
Figure 8.12
32
Induction
Figure 8.12
33
Induction
Figure 8.12
34
Repression
Figure 8.13
35
Repression
ANIMATION Operons Induction
ANIMATION Operons Repression
Figure 8.13
36
Catabolite Repression
Figure 8.14
37
  • Lactose present, no glucose
  • Lactose glucose present

Figure 8.15
38
Types of Bacterial sex
Name Process What it is Comments



39
Genetic Recombination
  • The rearrangement of genes.
  • Crossing over is where genes are recombined
    within a chromosome.

40
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41
Transformation
  • Naked DNA is transferred from one bacteria to
    another.
  • Was the first experiment that showed DNA was the
    genetic information

42
Genetic Recombination
Figure 8.25
43
Genetic Transformation
ANIMATION Transformation
Figure 8.24
44
Conjugation
  • DNA transferred from one bacteria to another by a
    sex pillus.
  • Information of transfer coded by a plasmid called
    F
  • Hfr cells occur when F plasmid goes into the
    host chromosome and recombines, it will then draw
    across the DNA.

45
Bacterial Conjugation
Figure 8.26
46
Conjugation in E. coli
Figure 8.27a
47
Conjugation in E. coli
Figure 8.27b
48
Conjugation in E. coli
Figure 8.27c
49
Transduction
  • DNA is passed from one bacterium to another in a
    bacteriophage and put into recipients DNA.

50
Transduction by a Bacteriophage
Figure 8.28
51
Alternate forms of the chromosome format.
  • Plasmids self replicating circular molecules of
    NDA
  • Transposes small segments of DNA that can move
    into different parts of the genome.
  • Can these have an effect on Evolution?

52
Control of gene expression
  • Repression
  • Induction

53
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54
The Operon Model of gene expression
  • Repression regulatory mechanism inhibits gene
    expression
  • Induction a process that turn on gene
    expression

55
Repressible Operon
56
Inducible operon
57
Where are the points of control
58
If a cell has all the genes that are needed then
why are they not expressed at one time?
59
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60
Mutations
  • What are they?

61
Mutations
  • What can they do

62
Mutation
  • A change in the genetic material
  • Mutations may be neutral, beneficial, or harmful
  • Mutagen Agent that causes mutations
  • Spontaneous mutations Occur in the absence of a
    mutagen

63
Mutation
  • Base substitution (point mutation)
  • Missense mutation
  • Change in one base
  • Result in change in amino acid

Figure 8.17a, b
64
Mutation
  • Nonsense mutation
  • Results in a nonsense codon

Figure 8.17a, c
65
Mutation
  • Frameshift mutation
  • Insertion or deletion of one or more nucleotide
    pairs

Figure 8.17a, d
66
The Frequency of Mutation
67
Chemical Mutagens
Figure 8.19a
68
Radiation
  • Ionizing radiation (X rays and gamma rays) causes
    the formation of ions that can react with
    nucleotides and the deoxyribose-phosphate backbone

69
Radiation
  • UV radiation causes thymine dimers

Figure 8.20
70
Repair
  • Photolyases separate thymine dimers
  • Nucleotide excision repair

Figure 8.20
71
Selection
  • Positive (direct) selection detects mutant cells
    because they grow or appear different
  • Negative (indirect) selection detects mutant
    cells because they do not grow
  • Replica plating

72
Replica Plating
Figure 8.21
73
Ames Test for Chemical Carcinogens
Figure 8.22
74
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75
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76
The old and new genetics
  • Screening and selection of mutants

77
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78
What do you think we would call the new genetics?
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