1. Microbial Genetics Methanococcus jannaschii

2. Chapter 9 Topics - Genetics - Flow of Genetics - Regulation - Mutation
- Recombination

3. The sum total of genetic material of a cell is referred to as the genome.
Fig. 9.2 The general location and forms of the genome

4. Figure 7.2 Bacterial genome-overview

5. Chromosome Prokaryotic Eukaryotic
Histonelike proteins condense DNA
Eukaryotic
Histone proteins condense DNA
Subdivided into basic informational packets called genes

6. Genes Three categories Genotype Phenotype Structural Regulatory
Encode for RNA
Genotype
sum of all gene types
Phenotype
Expression of the genotypes

7. Introduction
A. Gene – a segment of DNA that codes for a
protein.
B. Genetics – a study of genes or heredity, how
traits are passed from one
generation to the next.
C. Microbe traits that are heritable
1. Morphology – cell shape and arrangement.
2. Structures – capsules, flagella, endospores, cell wall type, etc.
3. Biochemistry – Enzymes, metabolic
pathways etc.

8. The prokaryotic chromosome
Only one chromosome, only one copy of the
genotype. Doesn’t deal well with deleterious
mutations. Makes up for this with bacterial
numbers and mutability.

9. Roles of DNA A. Replication B. Gene expression cell division
need accurate copy
B. Gene expression
DNA
RNA
Protein
Figure 6.2

10. Structure of DNA A. Two strands B. Nucleotides C. Double helix
1. Hydrogen bonds between strands
2. Neighboring deoxyribose connected
a. 3’ of one deoxyribose to 5’ of next deoxyribose
b. Phosphate in between
C. Double helix
D. Complimentary base pairing
G and C
A and T
Antiparallel strands
Figure 6.1

11. Structure Nucleotide Double stranded helix Phosphate Deoxyribose sugar
Nitrogenous base
Double stranded helix
Antiparallel arrangement

12. Nitrogenous bases
Purines
Adenine
Guanine
Pyrimidines
Thymine
Cytosine

15. DNA Replication A. Template Concept
Each side of a DNA molecule is a template for the synthesis of a new strand due to complementary base pairing

16. Semi Conservative Replication
Each half of the original strand is incorporated into the new double strand.

17. Events of replication
1. Origin/s
a. In prokaryotes = 1
b. In eukaryotes = many
2. Strand separation
a. Helicase- opens the strands
b. Single strand binding proteins – keeps
strands separated
c. Topoisomerases – keep DNA strands
from tangling up.
3. Building new strands
a. DNA polymerase I and III – adds in new
nucleotides
b. RNA primase – makes a short RNA primer on the
lagging strand
c. DNA ligase – binds Okazaki fragments

18. Enzymes Helicase DNA polymerase III Primase DNA polymerase I Ligase
Gyrase

19. The function of important enzymes involved in DNA replication.
Table 9.1 Some enzymes involved in DNA replication

20. topoisomerases

22. Bacterial chromosomes
Replication of circular
chromosome
1. Origin of replication
a. bubble forms
b. DNA unwinds
2. Replication occurs
in both directions
a. Two replication forks
b. Continues until replication forks meet
3. Strands separate
Figure 6.4

25. Fig. 9.6

26. Fig. 9.6a

27. Fig. 9.6b

28. Fig. 9.6c

29. Fig. 9.6d

30. Figure 7.8 The central dogma of genetics5´ 3´
DNA (genotype) 3´ 5´
Transcription
mRNA 5´ 3´
Translation by ribosomes
NH2
Methionine
Arginine
Tyrosine
Leucine
Polypeptide
Phenotype

31. RNA Transcription Codon Message RNA (mRNA) Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Codon

32. Transcription
A single strand of RNA is transcribed from a template strand of DNA
RNA polymerase catalyzes the reaction
Synthesis in 5’ to 3’ direction

33. mRNA Copy of a structural gene or genes of DNA
Can encode for multiple proteins on one message
Thymidine is replaced by uracil
The message contains a codon (three bases)

34. The synthesis of mRNA from DNA.
Fig The major events in mRNA synthesis

35. tRNA Copy of specific regions of DNA
Complimentary sequences form hairpin loops
Amino acid attachment site
Anticodon
Participates in translation (protein synthesis)

36. Important structural characteristics for tRNA and mRNA.
Fig Characteristics of transfer and message RNA

37. rRNA Consist of two subunits (70S)
A subunit is composed of rRNA and protein
Participates in translation

38. Ribosomes bind to the mRNA, enabling tRNAs to bind, followed by protein synthesis.
Fig. 9.9 Summary of the flow of genetics

39. Codons Triplet code that specifies a given amino acid
Multiple codes for one amino acid
20 amino acids
Start codon
Stop codons

40. The codons from mRNA specify a given amino acid.
Fig The Genetic code

41. Protein Translation Protein synthesis have the following participants
mRNA
tRNA with attached amino acid
Ribosome

42. Participants involved in the translation process.
Fig The “players” in translation

43. Figure 7.15 Prokaryotic ribosomes-overview

44. Translation Ribosomes bind mRNA near the start codon (ex. AUG)
tRNA anticodon with attached amino acid binds to the start codon
Ribosomes move to the next codon, allowing a new tRNA to bind and add another amino acid
Series of amino acids form peptide bonds
Stop codon terminates translation

45. For procaryotes, translation can occur at multiple sites on the mRNA while the message is still being transcribed.
Fig Speeding up the protein assembly line in bacteria

46. Figure 7.19 A polyribosome in a prokaryotic cell-overview

47. Regulation Lactose operon Repressible operon Antimicrobials sugar
Amino acids, nucleotides
Antimicrobials

48. Regulation of Genetic Expression
Nature of prokaryotic operons
An operon consists of a promoter and a series of genes
Some operons are controlled by a regulatory element called an operator
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49. Figure 7.20 An operon Operon Promoter Operator Structural genes
Regulatory gene 1 2 3 4 3´
5´ Template DNA strand

50. Regulation of Genetic Expression
Nature of prokaryotic operons
Inducible operons must be activated by inducers
Lactose operon
Repressible operons are transcribed continually until deactivated by repressors
Arginine operon
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51. The regulation of sugar metabolism such as lactose involves repression in the absence of lactose, and induction when lactose is present.
Fig The lactose operon in bacteria

52. The regulation of amino acids such as arginine involves repression when arginine accumulates, and no repression when arginine is being used.
Fig Repressible operon

53. Antimicrobials
Ex. Antibiotics and drugs can inhibit the enzymes involved in transcription and translation

54. Mutations Changes made to the DNA Spontaneous – random change
Induced – chemical, radiation.
Point – change a single base
Nonsense – change a normal codon into a stop codon
Back-mutation – mutation is reversed
Frameshift – reading frame of the mRNA changes

55. Mutations A. Mutation – any change in the DNA base sequence.
B. May be harmless, harmful, or beneficial
C. can only be passed to next generation if mutation occurs in sex cells, not somatic cells.

56. Causes
1. Spontaneous – errors in replication
2. Radiation (Sun, X-rays, nuclear bombs)
3. Chemicals (nicotine, formaldehyde)

57. Types of mutations
1. Point Mutations – addition, deletion, substitution of a single base – One nitrogenous base is changed. May not be so severe since only one base, but can be severe. EX. Sickle cell anemia.
2. Missense Mutation – base changes cause a different amino acid to be inserted and a protein is made but an incorrect one
3. Nonsense Mutation – base changes result in normal codon change into a stop codon so no protein is made due to an early stop signal
4. Neutral or Silent Mutations – no effect on protein product (base sequence is read differently, but still same protein sequence)

58. 5. Frameshift mutation
Insertion – one or more nucleotides is added to the
sequence.
Deletion- one or more nucleotides is lost in the sequence.
Frame-shift mutations are very severe because it throws off the entire reading frame of a gene.
THE FAT CAT ATE THE BIG RAT
THE FAC ATA TET HEB IGR AT

60. Effects of mutations Positive effects for the cell
Allow cells to adapt
Negative effects for the cell
Loss of function
Cells cannot survive

61. Ways bacteria acquire DNA information
Transformation – picking up DNA from the environment.
2. Conjugation – primitive “mating” in between bacteria
3. Transduction – Bacterial DNA carried from one bacteria to another by a bacteriophage.

63. 1. Transformation a. DNA exits one cell, taken up by another cell
1. Natural
2. few bacteria take up DNA fragments
b. Artificial--induced in laboratory
1. useful tool for recombinant DNA technology
Figure 6.20

64. Transformation
Nonspecific acceptance of free DNA by the cell (ex. DNA fragments, plasmids)
DNA can be inserted into the chromosome
Competent cells readily accept DNA

65. DNA released from a killed cell can be accepted by a live competent cell, expressing a new phenotype.
Fig Griffith’s classic experiment in transformation

66. 2. Conjugation a. Conjugative plasmids sex pilus connect two cells
Transfers plasmid
one cell F+
one cell F-
Figure 6.21

67. Conjugation cont.
3. linear strand is copied forming a complete plasmid
4. both cells are now F+
Figure 6.21

68. Conjugation
Transfer of plasmid DNA from a F+ (F factor) cell to a F- cell
An F+ bacterium possesses a pilus
Pilus attaches to the recipient cell and creates pore for the transfer DNA
High frequency recombination (Hfr) donors contain the F factor in the chromosome

69. Conjugation is the genetic transmission through direct contact between cells.
Fig Conjugation: genetic transmission through direct contact

70. 3. Transduction a. Bacteriophage 1. virus that infects bacteria
2. reproduce in bacteria
3. some phages contain bacterial DNA
rare event
transducing particle
4. cell lysis and release
normal phage
transducing particles
Figure 6.23

71. Transduction 5. Transducing particles 6. genetic exchange
infect other bacteria
inject bacterial DNA into new cell
6. genetic exchange
one bacteria cell to another
7. integration into chromosome
Figure 6.23

72. Transduction Bacteriophage infect host cells
Serve as the carrier of DNA from a donor cell to a recipient cell
Generalized
Specialized

73. Genetic transfer based on generalized transduction.
Fig Generalized transduction

74. Genetic transfer based on specialized transduction.
Fig Specialized transduction