1. Bacterial Genetics

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

3. Chromosome Subdivided into basic informational packets called genes
Procaryotic
Histonelike proteins condense DNA
Located in cytoplasm
Usually circular
Usually single chromosome

4. Chromosomes Eucaryotic Histone proteins condense DNA
Located in nucleus
Vary in number
Can be diploid (sister chromatids) or haploid
Appear elongate

5. Genes Part of DNA that encodes a protein Direct cell function
Basic unit of heredity
In general, linear sequence of nucleotides or codons with a fixed start and end point
Genes--> chromosomes-->organisms

6. Genes encoded by DNA Three categories Genotype Phenotype
Structural- encode proteins
Regulatory- control gene expression
Encode for RNA- rRNA or tRNA
Genotype
sum of all gene types
Phenotype
Collection or expression of traits encoded in an organism’s genotype

7. How genes effect heredity
Genotype
sum of all gene types
Phenotype
Collection or expression of traits encoded in an organism’s genotype

8. Central Dogma DNA RNA Protein replication translation transcription
Reverse
transcription

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

10. Nitrogenous bases
Purines
Adenine
Guanine
Pyrimidines
Thymine
Cytosine

11. Purines and pyrimidines pair (A-T or G-C) and the sugars (backbone) are linked by a phosphate.
Three views of DNA structure

12. Replication Semiconservative Enzymes Leading strand Lagging strand
Okazaki fragments

13. Semiconservative
New strands are synthesized in 5’ to 3’ direction

14. Semiconservative replication of DNA synthesizes a new strand of DNA from a template strand.
Simplified steps to show the semiconservative
replication of DNA

15. Steps in replication Uncoiling- unwinding of DNA from histones
Unzipping- breaking hydrogen bonds between base pairs allowing strands to separate
Addition of nucleotides- each parent strand is used as the template for synthesis of daughter strands. Read 3’-5’, synthesis 5’-3’

16. Enzymes

17. Leading strand
RNA primer initiates the 5’ to 3’ synthesis of DNA in continuous manner

18. Lagging strand Multiple Okazaki fragments are synthesized
Okazaki fragments are ligated together to form one continuous strand
Replication begins at the origin of replication

19. The steps associated with the DNA replication process.
The bacterial replicon: a model for DNA
Synthesis

20. Replication processes from other biological systems (plasmids, viruses) involve a rolling cycle.
Simplified model of rolling circle DNA
Replication

21. RNA Transcription Message RNA (mRNA)- protein Transfer RNA (tRNA)
Ribosomal RNA (rRNA)

22. Transcription
A single strand of RNA is transcribed from a template strand of DNA
Template strand- transcribed
Coding strand- nontranscribed
RNA polymerase catalyzes the reaction
In eucaryotes
RNAP I- rRNA
RNAP II- mRNA -->protein
RNAP III-tRNA

23. Eucaryotic mRNA mRNA can have interruptions Exon expressed sequences
Gene1
exon
intron
gene 1
exon
Exon expressed sequences
Intron intervening sequence
Removed by splicesosomes. Splicesosome loops the intron into lariat shape ,excises them, and joins exons. Some introns become endonucleases.

24. The processing of pre-mRNA into mRNA involves the removal of introns.

25. RNA Thymidine is replaced by uracil
Synthesis in 5’ to 3’ direction (with regard to RNA)
The message contains a codon (three bases)

26. Transcription Initiates when RNAP recognizes a promoter region
Two regions
1) 35 bp upstream from transcription start site
2) 10 bp upstream from transcription start site

27. Transcription
Terminates when RNAP reaches terminators in sequence. These make RNAP stutter and fall off or pause and fall off

28. The synthesis of mRNA from DNA.
The major events in mRNA synthesis

29. Transcription regulation
Operons- coordinated set of genes which are regulated as a single unit. They are transcribed as a single unit.
Types of operons
Inducible
Repressible

30. Regulator gene- gene that can repress the operon
Operator- acts as on/off switch
Structural gene- genes to be transcribed when the operon is on

31. Lactose operon (inducible)
Breaks down lactose
Normally in OFF position. Operon is controlled by the binding of the repressor to the operator
Lactose binding to repressor causes conformation changes in the repressor
Repressor dislodges from the operator
RNAP binds and transcribes structural genes

32. When lactose levels fall: the repressor is free to bind the operator again
In this system lactose is the inducer
This operon is not inducible in the presence of glucose. Glucose is preferred over lactose as a carbon source

33. The regulation of sugar metabolism such as lactose involves repression in the absence of lactose, and induction when lactose is present.
The lactose operon in bacteria

34. Repressible operon Operon is normally on
Corepressor- normally the product of the operon. Turns operon off by binding and activating the repressor

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

36. mRNA Copy of a structural gene or genes of DNA
Can encode for multiple proteins on one message
Thymine is replaced by uracil
The message contains codons
Carries code for proteins

37. tRNA Copy of specific regions of DNA Cloverleaf structure
Complimentary sequences form hairpin loops
Amino acid attachment site
Anticodon
Participates in translation (protein synthesis)
Delivers amino acid to growing polypeptide chain

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

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

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

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

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

43. Representation of the codons and their corresponding amino acids.

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

45. Participants involved in the translation process.
The “players” in translation

46. 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

47. The process of translation.
The events in protein synthesis

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

49. Transcription and translation in eucaryotes
Similar to procaryotes except
AUG encodes for a different form of methionine
mRNA code for one protein
Transcription and translation are not simultaneous
Pre-mRNA
Introns
Exons

50. Mutations Loss of bases Addition of bases Misincorporation of bases
Wild-type: natural, nonmutated strain
Mutant: harbors 1 or more mutations

51. 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

52. Examples of chemical and radioactive mutagens, and their effects.
Selected mutagenic agents and their effects

53. Ames test Salmonella culture (his-) cannot make histidine
Minimal media (his-)
+ test reagent
6 colonies
INDUCED + SPONTANEOUS
MUTANTS
Enriched media (his+)
18 colonies
TOTAL BACTERIA
Minimal media (his-)
3 colonies
SPONTANEOUS
MUTANTS

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

55. Recombination Sharing or recombining parts of their genome Conjugation
Transformation
Transduction

56. 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

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

58. 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

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

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

61. Genetic transfer based on generalized transduction.

62. Genetic transfer based on specialized transduction.

63. Transposon “Jumping genes” Exist in plasmids and chromosomes
Contains genes that encode for enzymes that remove and reintegrate the transposon
Small transposons are called insertion elements