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What are the minimum requirements that bacteria need for growth and metabolism?
- Carbon
- Nitrogen
- Energy (ATP)
- H2O
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Define Catabolism
Substrate breakdown & conversion into usable energy
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Define Anabolism
energy used in synthesis of cellular constituents
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Types of glucose metabolism (3)
- fermentation
- anaerobic respiration
- aerobic respiration
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A nucleotide sequence with biological function
gene
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DNA sequence occurring just before start of transcribed gene, site recognized by RNA Polymerase
promoter
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Can be bound by repressor proteins to prevent transcription
Operator
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A group of genes expressed from a particular promoter & ending at a transcription terminator
operon
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What is a haploid?
When a cell only has one copy of chromosome (bacteria)
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What is a bacteriophage?
A bacterial virus
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Steps of DNA Replication
- 1. Initiated at the OriC Sequence
- 2. Helicase then unwinds DNA at origin
- 3. Primase synthesizes primers to start the process
- 4. DNA polymerase synthesizes DNA bidirectionally
- 5. Ligase ligates the pieces together
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Steps of Transcription
- initiation: RNA polymerase binds to the promoter
- elongation: sequential addition of nucleotides complementary to sequence in the DNA
- termination: RNA polymerase dissociates from DNA
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What is a codon?
set of 3 nucleotides encoding an amino acid or start/stop codon
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Define wobble
wobble = degeneracy of the genetic code (3rd nucleotide can vary and still produce same amino acid)
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What is an anticodon?
- Anticodon = tRNA molecules containing sequence complementary to a codon sequence
- Allows base pairing & binds to codon sequence on mRNA
- Corresponding amino acid attaches to opposite end of tRNA
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Steps of Translation
1)Formation of initiation complex: Binding of 30S ribosomal subunit & initiator tRNA for Met at AUG
2)Initiation of mRNA synthesis: 50S Subunit binds complex
3)tRNA corresponding to 2nd codon occupies A site
4)Transpeptidation: A site amino acid binds to P site amino acid
5)Empty tRNA in P site released from ribosome
6)Ribosome moves down mRNA 3 nucleotides (tRNA with attached nascent peptide moves to P site, next codon moves to A site)
7)Termination: process continues until stop codon moves to A site (no corresponding tRNA)
Protein is released into cytoplasm; complex disassembles
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increased concentration of specific small molecules used to turn on genes (virulence factors)
Quarum sensing
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What is the function of the repressor?
prevents gene expression by binding to specific DNA sequence (operator), blocking RNA Pol from initiating transcription
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What is the function of the apoinducer?
binds DNA sequence & assists RNA Pol in initiation steps
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What is the function of the inducer?
substrate that induces operon to increase expression of enzymes necessary for its metabolism (lactose)
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Describe the lac operon
the inducible operon
•The lac operon encodes genes necessary for metabolism of lactose
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What does the CAP-cAMP complex do?
- enhances binding of RNA Pol to promoter
- increases transcription
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Describe the trp operon
•Repressible operon
•Encodes enzymes necessary for tryptophan biosynthesis
•Repressor protein is inactive until binding by tryptophan
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Attenuation-antitermination mechanism
Leader peptide (with 4 domains - #4 is an attenuator) - High conc. of Trp, terminator hairpin forms (no transcription)
w/o Trp, antiterminator hairpin forms (transcription occurs)
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What type of mutation has occurred if:
purine (A,G) replaced by another purine or pyrimidine (C,T) replaced by another pyrimidine
transition mutation
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What type of mutation has occurred if:
purine replaced by pyrimidine or vice versa
transversion
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Types of DNA Repair
- Direct
- Excision Repair
- Recombinational
- SOS
- Error Prone repair
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DNA Repair: DIRECT
Enzymatic removal of damage (pyrimidine dimers)
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DNA Repair: EXCISION REPAIR
Excises mutated DNA segment and synthesizes new strand
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DNA Repairs: RECOMBINATIONAL
when both strands are damaged, retrieval of missing information by recombination
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DNA Repair: SOS
induction of many genes
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DNA Repair: ERROR PRONE REPAIR
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Genetic Transfer Mechanisms:
Transformation
acquisition of genes by incorporation of foreign DNA
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Genetic Transfer Mechanisms:
Transduction
transfer from one bacterium to another by bacteriophage
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