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Micro Test 2
Terms in this set (102)
The whole of the genetic information of an organism
segments of DNA that code for proteins
genetic makeup of an organism
expression of the genes
How do plasmids and chromosomes differ?
A plasmid is a small, often circular DNA molecule found in bacteria and other cells.
Plasmids are separate from the bacterial chromosome and replicate independently of it.
What are noncoding regions of DNA (short tandem repeats) used for?
Used in DNA fingerprinting
Explain Vertical vs. horizontal gene transfer
Vertical gene transfer - parent to offspring - it's through either sexual or asexual reproduction.
Horizontal gene transfer - movement of genetic info between organisms that are not parent/offspring
DNA replication (understand well enough to label a basic picture):
Major Enzyme used?
DNA polymerase is the major enzyme used.
How do nucleotides pair?
A, T, C, G
leading vs lagging strand
Leading: synthesized continuously into the widening replication fork. Runs 5'-3'
Lagging: replicates away from the fork, must wait until it widens to polymerize and is discontinuous, leading to Okazaki fragments
Why do leading and lagging strands exist?
Because of the different directions the two enzymes move on the lagging strand, the DNA chain is only synthesized in small fragments. ... Hence it is called the lagging strand.
How does DNA replication differ from protein synthesis: # DNA strands copied, how much is copied
DNA Replication - purpose is for reproduction, both strands copied, and DNA polymerase binds bases.
Protein Synthesis - purpose is for protein synthesis, one strand copied, and RNA polymerase binds bases.
RNA types: where are they found, what do they do
rRNA - intergral part of ribosomes
tRNA - transports amino acids during protein synthesis
mRNA - carries coded info from DNA to ribosomes
Protein Synthesis (understand transcription & translation well enough to label simple diagram):
Know steps in order AND where each step occurs for prokaryotes vs. eukaryotes
DNA unravels, exposing code.
mRNA comes in.
transcription (copying genetic code from DNA)
mRNA exits nucleus, goes to ribosome.
translation (gives message to ribosome)
tRNA brings in specific amino acids (anticodons)
protein synthesis begins.
What nucleotide binds to adenine in RNA?
Major enzyme used in protein synthesis
Where does RNA polymerase bind during transcription?
What tells RNA polymerase when to stop?
3 mRNA nucleotides that code for amino acid:
Tell me what a start codon & stop codon does
Start codon - begins reading
Terminator - ends reading
What is an anticodon?
An anticodon is the three unpaired bases on a tRNA that is complementary to one mRNA.
What does degeneracy mean?
many codons code for the same amino acid
Why can translation begin in bacteria before transcription is complete?
Because it takes place in the cytoplasm
Exons and Introns: know function of each; what organisms do it
Exons - expressed DNA
Introns - noncoding regions
Gene Expression in bacteria: why is it beneficial turning genes on or off?
Genes are turned on and off in different patterns during development to make a brain cell look and act different from a liver cell or a muscle cell, for example. Gene regulation also allows cells to react quickly to changes in their environments.
What is a constitutive operon?
A gene that is always on, like regulatory genes.
What is an inducible operon?
operon that is usually off and only turned on when needed.
What is a repressible operon?
An operon that is usually on, but can be inhibited when a molecule, like tryptophan binds to a regulatory protein.
What is an operon?
group of genes that is transcribed together and controlled by one promoter
What is a promoter?
binding site for RNA polymerase
What are structural genes?
genes that code for proteins
What are regulatory genes?
A gene that produces repressor proteins.
What is a repressor
a protein that binds to the operator and prevents transcription. Genes only turned off when needed.
What is an operator?
a segment of DNA to which a repressor binds
How pre-transcriptional control differs from post-transcriptional control
Pre-transcriptional - transcription must be turned on via induction, once turned on must be turned off via repression.
Post-transcriptional - removes introns that do not code for proteins.
· Default position?
· What must be present to "induce"
· Example in E. coli? What does this operon do?
Will only be switched on when lactose is present and glucose isn't.
The lac operon produces the necessary enzymes needed to breakdown lactose. If lactose isn't present, the repressor binds to operator, keeping it off, and preventing transcription.
· Default position?
· What causes a change in gene expression? Hint: Co.....re....press
· Example in E. coli? What does this operon do?
Default: on until turn off.
Corepressor binds to inactive repressor to stop transcription.
The trp operon responds to a repressor protein that binds to two molecules of tryptophan. ... This binding prevents the binding of RNA polymerase, so the operon is not transcribed
Positive regulation (differs from simple inducing and repressing. Changes RATE of expression)-be able to tell me the status of glucose and lactose in this system
Mechanism that allows bacteria to digest other sugars when glucose is running low. When glucose is low, CAMP increases, which in in turn turns on the lac operon if lactose is present.
Epigenetic Inheritance: How are genes turned off, is it permanent?
Genes can be turned off by methylating nucleotides and passed to offspring. The genes can be turned back on in offspring.
mRNA + substrate= changes part of the mRNA structure. This is called:
Single-stranded RNA that binds to mRNA. What are they called?
Mutations: What are they? Are they all bad?
A permanent change in the base sequence of DNA.
Not all are bad.
Point mutations: know difference between silent, missense, nonsense
Silent mutation - doesn't affect gene or its expression.
Nonsense - base substitution codes for a STOP codon.
Missense - base substitution codes for another amino acid.
Do mutagens have to be present for mutations to occur?
What is a mutagen and the types of mutagens we discussed
· What does nitrous acid do?
· What do nucleoside analogs do?
Mutagen - environmental agent responsible for mutations.
Nitrous acid - causes adenine to bind with cytosine rather than thymine. So A-C instead of A-T
Nucleoside analogs - incorporates into DNA in place of a normal base, causes mistakes in base pairing.
Types of plasmids: what are they, what do they carry genes for
plasmids are self-replicating circular pieces of DNA.
Often code for proteins that enhance the pathogenicity of a bacterium
Types of plasmids (factors)
Conjugative plasmid (F factor):
Resistance factors (R factors):
Conjugative plasmid (F factor):carries genes for
sex pili and transfer of the plasmid.
Dissimilation plasmids: encode enzymes for the
catabolism of unusual compounds
Resistance factors (R factors): encode antibiotic
How was the plasmid for antibiotic resistance discovered? Anything else unique noticed during this discovery?
How is a transposon different from a plasmid?
Transposons are segments of DNA that can move
from one region of DNA to another.
plasmids transfer genetic material between genomes, whereas transposons transfer genetic material between chromosomes within same genome.
Explain the three different genetic transfer pathways
Transformation: genes transferred from one
bacterium to another as "naked" DNA.
Conjugation: plasmids transferred from
one bacterium to another - cell to cell contact via sex pili.
Transduction: transfer of DNA from one plasmid to anothe via bacteriophages.
What experiment led to discovery of transformation? Know the basic steps and how it showed transformation was occurring.
Griffith's Experiment -
Streptococcus with a capsule is deadly to mice.
Genes from the dead bacteria had entered the cells and changed them genetically.
Each mouse was injected, one with smooth strain (died), rough strain (lived), heat kill smooth strain (lived), and one with rough strain and heat killed smooth strain.
The other bacteria picked up the genes from the dead bacteria, changing its genome and therefore becoming capsulated and killing the mouse.
Requirements of conjugation
cell-to-cell contact via sex pili
Conjugating cells must be of opposite mating type
What is competence? F+? F-? Hfr?
When the bacteria is in a physiological
state where it can take up the DNA.
Hfr (high frequency of recombination) cells,
the F factor integrates on the chromosome converting an F+ cell into an Hfr cell.
F+ donor, F- recipient - creating two F+.
Then when an F factor becomes integrated into the F+ it becomes the Hfr.
Transduction: What transfers the DNA in this pathway;
DNA is transferred from a donor cell to a recipient via a
Differences in microbial Growth requirements
· Growth curve for temperature: Be able to interpret a growth curve
Chemical requirements for microbial growth:
Carbon - used for energy
Nitrogen - protein, DNA and ATP
Sulfur - Amino Acids
Phosphorus - DNA, RNA, ATP
Classification based on oxygen use:
can live with or without oxygen
Unable to use O2 and possibly harmed by it
Tolerate O2 but cannot use it
require oxygen concentration lower than air
Compare selective media and differential media?
Selective media - suppress unwanted microbes/encourage growth of desired microbes
Differential - allow for distinguishing and different microbe growth on same plate
ability to detect and respond to cell population density by gene regulation
Benefits for bacteria living in a biofilm?
Where can they be found?
Found on smooth surfaces, teeth, catheters, heart valves.
Bacterial Division: Binary Fission vs. Budding
Binary Fission - DNA replicate, cell wall pinched, then cells separate, increases number of cells.
Budding - creates a new bud.
Phases of growth in order:
Lag - preparing for growth, no increase in pop.
Log - drastic increase in pop.
Stationary - bacteria approach the carrying capacity.
Death - pop die.
Methods for measuring microbial growth?
Plate count -
Most probable number -
Direct microscopic count -
plate - dilute and plate
filtration - pass through fine filter and grow on dish
MPN - multiple lactose tubes
Direct - use special cell counter
Major stages of Carbon cycle (how organisms use carbon so you can tell me what kind of organism (i.e., chemoheterotroph, photoautotroph) is converting it at each stage)
Bacteriostatic vs. Bactericidal
Bacteriostatic - inhibit growth of bacteria, not killing them.
Bactericidal: kills microbes.
Microbial Control Agents: How does dry heat sterilization kill the microbe?
Dry heat sterilization kills by oxidation. By flaming, incineration, hot-air sterilization.
disk diffusion method
Evaluates efficacy of chemical agents
We look for the zone of inhibition and can see how well each antibiotic works.
an interdependent relationship
The use of organisms to detoxify and restore polluted and degraded ecosystems.
Major stages of Nitrogen Cycle--Able to recognize when ammonification, nitrification, and denitrification occur in the cycle (see diagram from class- don't have to know chemical structure)
Ammonification - release of ammonia by bacteria and fungi
Nitrification - oxidation of ammonium ions to produce nitrate
Denitrification - nitrate used as electron acceptor by microbes in absence of O2.
Nitrogen-fixation converts atmospheric Nitrogen into:
What is a lichen? Which cycle are they important in?
Combination of fungus and algae or cyanobacteria
In freshwater aquatic systems (review zones), where might you find photosynthetic algae? Microbes that use very little O2? How about no light and O2?
Littoral - along shore
Limnectic - surface of open water, photosynthetic algae
Profundal - deeper water under limnetic zone, low O2.
Benthic - bottom sediment, no light or O2.
In saltwater aquatic systems, what microbes make up most of oceans (below 100 meters)?
What organisms do luminescent bacteria live on?
What is eutrophication? What causes an algal bloom?
Is an abundance of nutrients that causes a dense growth of plant life and death of animal life from lack of oxygen.
Excessive nitrogen and phosphorus
What are coliforms? How do we use them in sanitation?
Coliforms are fecal particles that can be found in drinking water.
The presence of fecal coliform in a drinking water sample often indicates recent fecal contamination, meaning that there is a greater risk that pathogens are present than if only total coliform bacteria is detected.
Major steps of water treatment
Flocculation - removal of colloidal materials, bacteria, and viruses by adding alum
Filtration - passing water through fine sand or coal
Disinfection - using ozone, chlorination, or UV light
major steps in sewage treatment
Primary - removal of solids
Secondary - activated sludge system and trickling filters.
Disinfection - sewage disinfected by chlorination.
During commercial canning, what organism are they targeting during sterilization?
What can be caused by C. botulinum?
Difficulty breathing, paralysis, or even death
How does thermophilic anaerobic spoilage differ from flat sour spoilage?
Thermophilic - cause gas (swelling of can) and sour food.
Flat sour - no gas but sour food
Can mesophilic bacteria spoil canned goods? How?
Yes, in leaking cans. External bacteria introduced during sealing process.
How do they sterilize packaging that can't undergo extreme heat treatment?
Through aseptic packaging, usually with super-heated steam or high-energy electron beams
What kind of radiation is used to sterilize food?
X-rays; used to inactivate trichinella spiralis.
What is pascalization? What is it used on?
High-pressure food preservation, for pre-wrapped foods (Fruits, deli meats) submerged in tanks of pressurized water.
1. Cheese, butter, and yogurt are all possible because of bacteria producing:
1. Non-dairy food/beverage products: Most possible due to sugars being ___________ by yeast in _____________ fermentation.
Why can translation begin in bacteria before transcription is complete?
Everything takes place in the cytoplasm
Which type of genes are always on; sometimes called housekeeping genes?
An inducible operon is an example of:
During protein synthesis, the enzyme that copies DNA binds to the:
Which type of horizontal gene transfer of bacteria involves a bacteriophage?
Which would accurately describe a microbe that could only live in environments free of oxygen?
Which type of post-transcriptional control is a single stranded RNA that inhibits protein production in eukaryotes?
Which type of plasmid allows bacteria to digest unusual compounds?
What experiment led to the discovery of transformation?
Disk Diffusion Method
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