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micro test 2
| Question | Answer |
|---|---|
| Common Additives of Media? | -Peptone -Yeast Extract -Chocolate -Blood -Casein Hydrolysate |
| What is Defined Media? | to determine what exactly is in it |
| What is Complex Media? | Less defined |
| What is selective Media? | Selects what to grow. Encourages and Discourages |
| What is differential media? | Differentiates by the way it looks |
| What is anaerobic media? | Can't tolerate oxygen |
| What is transport media? | Used with clinical samples |
| What are the nutritional growth requirements for bacteria? | Carbon Oxygen Nitrogen Hydrogen |
| Characteristics and usage of bacteriophage | Virus that infects and replicates within bacteria |
| pH at Which Microbes Grow Best | 7 (neutral) |
| Purpose of Agar in Nutrient Agar | To customize the media for the specific bacteria so that growth medium is as close as possible to natural environment |
| types (genera) of bacteria that form spores: | Gram-positive bacteria. Bacillus clostridium. |
| Mannitol Salt Agar – type of media and meaning | Selective-Alcohol carb utilized by staph and salt that inhibits other bacteriosis |
| Methylene Blue-type of media and meaning | Selective-Carbs promote growth of E-coli and gram negative die, inhibit gram positive |
| Macconkey -type of media and meaning | Differential-contain lactose, neutral red and crystal violet and dye inhibits gram positive |
| Optimal Temperatures for psychrophiles | below 25C |
| Optimal Temperatures for Mesophiles | Between 25C and 40C (This includes most human pathogens) |
| Optimal Temperatures for Thermophiles | above 40C |
| What is the lag phase? | preparing for division. Grow in size and metabolically active, but not reproductive |
| What is the log phase? | reproductively active. Increase in number. Symptoms appear due to cell/tissue damage |
| What is the stationary phase? | equalization; reproductive and death rates are equal; number of living cells are constant; immune system has been activated |
| What is the death/decline phase? | cell death; death rate higher than reproductive rate (log decrease) |
| What methods are direct to measure microbial growth? | 1)Viable plate counts 2)Membrane filtration 3)Microscopic counts 4)Electron counters 5)Most probable number |
| What methods are indirect to measure microbial growth? | 1)Metabolic activity 2)Dry weight 3)Turbidity |
| Steps of Viral Replication | -Attachment -Penetration -Biosynthesis -Maturation -Release |
| The structure that all viruses possess | A core of nucleic acid and a protein coat |
| Cytopathic effects that are cytocidal | All cytopathic effects are cytocidal. Cytopathic effects occur when a cell is invaded and bursts (dies). |
| Features of oncogenes (genes that transform a cell): 1/3 | -May provide genetic codes for growth factors to stimulate uncontrolled reproduction |
| Features of oncogenes (genes that transform a cell): 2/3 | -May program development of protein receptors that receive extracellular messages to nucleus at rapid rate |
| Features of oncogenes (genes that transform a cell): 3/3 | -May become incapable of producing substances that turn off cell growth |
| Methods of culturing viruses: | -Animal inoculation -embryonated eggs -tissue culture -organ culture -explant culture -cell culture -primary culture -diploid culture -continuous culture |
| Characteristics of a prophage: | A prophage is a viral genome inserted into the host cell DNA which then either integrates or exists as an extrachromosomal plasmid. They are the main component of viral gene transfer. |
| What is formaldehyde used for? | Formaldehyde is a chemical agent used to inactivate a virus by altering its genome |
| What is meant by a slow viral infection? | A slow viral infection is characterized by a very prolonged incubation period and a prolonged, slowly progressive clinical course. |
| Examples of slow viral infections: | Herpes, shingles from chicken pox |
| When is the cytopathic effect seen? | The cytopathic effect (CPE) is seen when a virus replicates |
| Support for the idea that viruses are nonliving: | Viruses cannot reproduce themselves outside of a host. |
| How bacteriophages contribute to bacterial virulence | By giving a new gene sequence to the host bacteria |
| How and when are viral envelopes acquired? | How: By budding off from a host cell. They gain the envelope from the host's lipid bilayer (cell membrane) When: Envelopes are acquired when a virus leaves a cell |
| Order of assembly of viral components of a cell: | 1. Assembly of the capsid (the capsid is also referred to as a protein capsule) 2. Association with the nucleic acid. |
| Factors that regulate the ability of a virus to infect an organism: | A virus can infect any living organism, including plants. |
| Effects of mutagenic agents on bacteria | always change the genotype (genes) |
| Important genes carried on plasmids: | |
| The use of the Ames test: | Used to determine if a substance is mutagenic by testing its ability to induce mutations in bacteria based on the finding that 90% of human carcinogens cause mutations |
| Example of the Ames test | in bacterial salmonella typhimurium that cannot metabolize histidine is placed on histadine medium and carcinogen is added mutations restoring histidine metabolism occur easily, and colonies grow if substance is carcinogenic |
| Characteristics of plasmids | closed loops separate from the bacterial DNA, Self replicating without help of bacterial DNA, and common in gram negative bacteria |
| What types of genes exist on plasmids | |
| How nitrous acid causes mutations: | converts adenine to hypoxanthine, hypoxanthine pairs with cytosine instead of thymine causes mRNA to code for guanine (not adenine). |
| Characteristics of the bacterial chromosome: | a. Single double helix in a closed loop b. Not enclosed by a membrane c. Tightly coiled: when unraveled, about 1 mm long. |
| Point mutation: How does it affect gene expression? | base substitution; changes a single codon only. |
| Frameshift mutation: How does it affect gene expression? | insertion or deletion of a base; changes entire sequence thereafter. |
| Differences between conjugation, transformation and transduction: | Transformation involves acquisition of DNA from the environment, conjugation involves acquisition of DNA directly from another bacterium, and transduction involves acquisition of bacterial DNA via a bacteriophage intermediate. |
| Components of an operon | Inducible operons – must be activated by inducers (Lactose Operon) Repressible Operons – transcribed continually until deactivated by repressors (Tryptophan Operon) |
| How mutations in overlapping genes may affect protein production: | |
| Use of restriction enzymes | Specific endonucleases used to cut DNA @ specific sites |
| Uses of genetic engineering and recombinant DNA technology: | Chemical production ( insulin, interferon, human growth hormone, tissue plasminogen activator), animal gene alterations, gene probes |
| First 2/4 Steps used to produce a recombinant vector: | (1) Ligase anneals the fragments to produce a recombinant plasmid (2) After the recombinant plasmid has been inserted in a bacterial cell |
| Steps 3 and 4 used to produce a recombinant vector: | (3) the bacteria are grown on a medium containing the antibiotic (4); only those cells that contain the recombinant plasmid (and thus the human growth hormone gene as well) can grow on the medium. |
| Purpose of PCR (polymerase chain reaction) | Produce a large number of identical molecules of DNA in vitro |
| Gene library purpose, what it’s used for and what it consists of: | Entire genome of an organism is cut with restriction enzyme (frequent cutter) Ligated into vector (plasmid or phage)Transformed into bacterial cells and store for future use |
| Uses for Southern Blot: | Used to transfer DNA fragments from a gel to a nylon membrane |
| Temperatures used and steps in PCR (polymerase chain reaction) | 1. Denaturation – heat to 94*C 2. Priming – cool to 65*C 3. Extension – 72*C 4. Repeat |
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