Exam 2 Study Guide
Exam 2 Study Guide BIO 208
Popular in Introduction to Microbiology
verified elite notetaker
Popular in Biology
verified elite notetaker
This 7 page Study Guide was uploaded by Crysta Meekins on Saturday March 5, 2016. The Study Guide belongs to BIO 208 at University of Kentucky taught by Dr.Richard in Winter 2016. Since its upload, it has received 28 views. For similar materials see Introduction to Microbiology in Biology at University of Kentucky.
Reviews for Exam 2 Study Guide
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 03/05/16
Chapter 8 Define gene and genome. ● gene: a segment of DNA encoding a functional product ● genome: one complete copy of the genetic information in a cell Describe the process of DNA replication, including the functions of helicase, ligase, primase, and DNA polymerase. How does base pairing of a DNA molecule make replication easier? How does synthesis of the leading and lagging strands differ? DNA replication ● the two strands of the double helix separate at the replication fork, and each strand is used as a template by DNA polymerases to synthesize new strands of DNA according to the rules of complementary base pairing. The result is two new strands of DNA. 1. Double stranded DNA is unwound by helicase. 2. Proteins bind to the DNA in order to stabilize the single strands. 3. Primase synthesizes an RNA primer. 4. DNA polymerase catalyzes formation of a sugarphosphate bond between neighboring nucleotides. 5. Hydrogen bonds form between the complementary bases. *Helicase: unwinds double helix *DNA polymerase: synthesizes DNA by copying a DNA template *Primase: RNA polymerase that makes RNA primers from a DNA template *Ligase: covalently bonds a carbon atom of one nucleotide with the phosphate of another nucleotide; okazaki fragments, and new segments in excision repair Describe protein synthesis, including transcription, RNA processing, and translation. What is the role of the promoter, terminator, mRNA, and RNA polymerase in transcription? What is the role of ribosome and the start and stop codons in translation? Transcription ● the synthesis of a complementary strand of RNA from a DNA template. 1. RNA polymerase binds to the promoter, and DNA unwinds at the beginning of the gene. 2. RNA is synthesized by complementary base pairing of free nucleotides with the nucleotide bases on the template strand of DNA. 3. The site of synthesis moves along DNA, DNA that has been transcribed rewinds. 4. Transcription reaches the terminator. 5. RNA and RNA polymerase are released, and the DNA helix reforms. *Promoter: the starting site on a DNA strand for transcription of RNA by RNA polymerase. *Terminator: the site on a DNA strand at which transcription ends. *mRNA: directs the incorporation of amino acids into proteins *RNA polymerase: copies RNA from a DNA template The sequence of codons on an mRNA molecule determines the sequence of amino acids that will be in the protein being synthesized. Each codon “codes” for a particular amino acid. The start codon initiates the synthesis of the protein molecule. Define operon and be able to discuss how expression is regulated in inducible and repressible operons. Operon: the operator and promoter sites and structural genes they control. Inducible operons ● normally OFF ● OFF= something bound to operator ● repressor is active by default ● In the absence of lactose, the repressor binds to the operator site. If lactose is present, the repressor binds to a metabolite of lactose instead of to the operator. Repressible operons ● normally ON ● ON= something isn’t bound to operator ● repressor is inactive by default ● tryptophan operon: repressible operons are turned OFF when the corepressor activates the repressor Types of mutations ● silent: results in no change in amino acid ● missense: results in change in amino acid ● nonsense: results in early STOP codon ● frameshift: an insertion or deletion of a base that alters the reading frame How do mutagens affect the mutation rate? A mutagen usually increases the spontaneous rate of mutation Outline the methods of positive and negative selection of mutants. How would you use positive selection to isolate an antibioticresistant bacterium? How would you use negative selection to isolate auxotrophic mutant bacterium? positive selection: trying to isolate bacteria that are resistant to antibiotic negative selection: only mutants won’t grow What is the purpose of the Ames test. What is the principle behind it? Uses bacteria as carcinogen indicators. To find mutagens or carcinogens. Types of Horizontal Gene Transfer Transformation ● genes are transferred from one bacterium to another as “naked” DNA in solution ● cells that take up naked DNA are competent results from alterations in cell wall and cytoplasmic membrane that allow DNA to enter cell Transduction ● transducing phage (viruses) carries random DNA segment from donor to recipient. bacteriophage viruses infect bacteria Conjugation ● mediated by a plasmid containing the F factor (fertility factor) ● requires physical contact (pilus or mating bridge) between the recipient cells shares plasmid Why do bacteria have plasmids? What types of genes do plasmids carry? ● Plasmids can contain resistances, virulence factors, or fertility genes. ● Plasmids are selfreplicating circular molecules of DNA carrying genes that are not usually essential for the cell’s survival. Chapter 6 Why is the bacterial growth curve usually plotted logarithmically? the numbers double each generation ● logarithmic: straight line ● arithmetic: slight curve The bacterial growth curve is exponential. Under ideal conditions. Know the 4 phases of the bacterial growth curve and what happens in each. ● lag phase: no growth ● log phase: maximum growth ● stationary phase: the number of cells dividing equals the number dying ● death phase: decrease in bacterial population Know the basic technique, advantages and disadvantages of the ways to quantify bacterial growth. Direct ways ● plate growth A method of determining the number of bacteria in a sample by counting the number of colonyforming units on a solid culture medium. advantage measures number of viable cells disadvantages takes 24 hours to grow colonies on the plates not used in food industry, too slow ● Direct microscope count A measure volume of a bacterial suspension is placed within a defined area on a microscope slide disadvantages difficult to count motile bacteria difficult to distinguish live from dead bacteria dvantages no wait time Indirect ways ● Turbidity The cloudiness of a suspension *instrument used: spectrophotometer disadvantages can’t read concentrations below 10 million cells/ 1 mL Osmotic pressure can cause plasmolysis (shrinking of the cell in hypertonic environments) Extreme or obligate halophiles (love salt) require high osmotic pressure Facultative halophiles tolerate high osmotic pressure Know the preferred growth conditions (temperature, pH, osmotic pressure) of the following groups of microbes and the effects of these growth conditions (altered enzyme shape, plasmolysis). ● thermophiles (heat loving) optimum growth : 50 degrees60 degrees Celsius ● psychrophiles (cold loving) grows best at about 15 degrees Celsius and does not grow above 20 degrees Celsius ● mesophiles (moderate temp loving) grows between about 10 degrees Celsius and 50 degrees Celsius ● acidophiles grows below pH 4 What are the chemical requirements for growth of the following: ● Heterotrophs/autotrophs H: requires an organic carbon source A: uses carbon dioxide as its principal carbon source ● Chemotrophs/phototrophs C: uses redox as its primary energy source P: uses light as its primary energy source What is the difference between a pure culture and a mixed culture? How can you use differential media, enrichment media, or streaking to isolate a pure culture from a mixed one? ● A pure culture contains one cell and a mixed culture contains many cells. ● Differential media: growth of one type of bacteria is distinguishable from others ● Enrichment media: growth of one type of bacteria is encouraged (only allows certain bacteria to grow) ● Streak plate method: to find what is present in the culture. Chapter 7 Why is the bacterial death curve usually plotted logarithmically? The death rate is constant What factors are important to consider when determining how to kill microbes (What’s the item? What is its purpose? What organism are you trying to kill? How many organisms are you trying to kill?) 1. What? Disinfection/sanitization ● high heat ● harsher chemicals Degerming/antisepsis ● nothing that will damage tissue 2. Why? ● normal use ● surgical or commercial use 3. What? ● Prions, spores, Gram , Gram + 4. How many organisms? Know the physical methods of controlling microbial growth: ● Heat TDP: lowest temperature at which all cells in a culture are killed in 10 min TDT: time during which all cells in a culture are killed moist heat denatures proteins Autoclave= most heat+pressure *more efficient & bactericidal ● Filtration used to sterilize liquids ● Low Temps inhibits microbial growth bacteriostatic ● Desiccation suspends microbial metabolism bacteriostatic: stops growth ● Osmotic Pressure causes plasmolysis ● Radiation can kill microbes UV light: 1x10^9 nm, very high energy How is KirbyBauer disc diffusion method used to evaluation the effectiveness of chemicals in killing microbes? A disk of filter paper is soaked with a chemical and placed on an inoculated agar plate; a zone of inhibition indicates effectiveness.
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'