Microbiology Chapter 7/8
Microbiology Chapter 7/8 2300
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This 7 page Class Notes was uploaded by Lauren Dennis on Thursday September 8, 2016. The Class Notes belongs to 2300 at Georgia State University taught by Dr. Fuhua Lu in Fall 2016. Since its upload, it has received 17 views. For similar materials see Microbiology 2300 in Microbiology at Georgia State University.
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Date Created: 09/08/16
Chapter 7/8: Microbial Genetics Genome: complete set of genetic information o Functional unit: gene o Study of transfer of genes: genetics o Study of DNA: genomics Flow of genetic information: o Vertical gene transfer: reproduction Sexual and asexual DNA RNA Protein DNA to RNA: transcription RNA to Protein: translation o Horizontal gene transfer: transfer of genes between cells of the same generation Transformation, transduction, and conjugation DNA: Deoxyribonucleic Acid: o Polymer of nucleotides o Bases: adenine, guanine, cytosine, thymine o Sugar: Deoxyribose o Two component Strands: Adenine (purine) to thymine (pyrimidine) 2 hydrogen bonds Guanine (purine) to cytosine (pyrimidine) 3 hydrogen bonds o bacterial DNA: circular one zone of replication bidirectional RNA: Ribonucleic Acid: o Polymer of nucleotides o Bases: adenine, guanine, cytosine, uracil o Sugar: ribose o Three different types: mRNA, rRNA, tRNA o RNA is an intermediate step from transcription to translation of DNA to a protein Two strands in Bacterial Transcription: o (-) strand: template for RNA synthesis resulting RNA molecule is complementary to this strand o (+) strand: complementary to the (-) strand nucleotide sequence of the RNA molecule is the same Uracil rather than thymine RNA: mRNA, tRNA, rRNA o Transcription: DNA to RNA RNA polymerase binds to promoter sequence Proceeds in 5’ to 3’ direction Stops when it reaches terminator sequence o Translation: Protein synthesis: mRNA to protein mRNA is translated to codons 3 nucleotides for 1 amino acid tRNA contain specific amino acids and anticodons mRNA start codon: AUG stop codon: UAA, UAG, UGA o Regulation of Gene Expression Constitutive enzymes expressed at fixed rates Other expressed when needed: Repressible: produced continuously unless production is repressed by an inhibitor Inducible: expressed only under adaptive conditions Bacteria Ribosome: o Unit: 70s o 2 subunits o no introns in the sequence o Transcription and Translation Done in the cytoplasmic region Can be done at the same time Bacteria is circular Major Differences: Mutation: o Change in genetic material Neutral, beneficial, or harmful Auxotroph: growth factor required Prototroph: no growth required o Spontaneous Mutation: Absence of a mutagen o Base Substitution Point mutation Missense: change in one base Different amino acid Nonsense: Results in a stop codon o Frameshift: Insertion or deletion of one or more nucleotide pairs o Mutagen: agent that causes a mutation Chemical or radiation UV light or Xrays o Chemicals: base pair mutagens, nucleoside analogs, frameshift o Ionizing Radiation: causes the formation of ions that can react with nucleotides and deoxyribose Repair of Damaged DNA: Mutant Selection o Positive (direct) selection: detects mutant cells because they grow or appear different Ames Test: measures the effect of chemical on reversion of histine- requiring Salmonella (auxotroph) o Negative (indirect) selection: detects because they do not grow Genetic Transfer and Recombination o Exchange of genes between two DNA molecules to form new combinations of genes on a chromosome Transformation: genes transferred into bacteria as a ‘naked’ DNA in a solution Griffith experiment: demonstrates genetic transformation o Using various components of killed Salmonella proved DNA was the carrier of genetic transformation Conjugation: genes transferred through F. pili from donor bacteria to recipient bacteria Translation: genes transferred into bacteria through bacteriophages Plasmids: o Conjugative: carries genes for sex pili and transfer of the plasmid reproduction o Dissimilation: encode enzymes for catabolism of unusual compounds Oil spill o R Factors: encode antibiotic resistance E. coli; helps create the resistance for new generations Transpoons o Segments of DNA that can move from one region of DNA to another Copy and paste o Contains insertions sequences for cutting and resealing of DNA Cut and paste o Complex transpoons carry other genes o Insertion sequence: transpose genes flanked by short repeat sequences o Composite: recognizable gene flanked by insertion sequences Generalized Transduction: by chance o Bacteria infects the host Bacteriophage Use host cells to create many bacteriophage Creates fragments of DNA o While packing the DNA they accidently pack the host DNA When replicating again the host cell is created while not creating bacteria Gene Expression and Environmental Functions: o Signal transduction: process that transmits information from external environment to inside cell Allows cells to respond to changes o Two component regulatory systems: Sensors recognize change in environment Response regulators activate or repress gene expression o Quorum sensing: density of the population enables activation o genes beneficial to mass Natural Selection o Mechanism to enhance survivability Antigenic variation N. gonorrhoeae changes numerous surface proteins Phase variation Routine switching on and off of genes Altering expression allows portions of population to survive and multiply