207 Questions
In a standard growth curve, what phase represents when the number of cells growing and dying are equal?
Stationary Phase
Which enzyme catalyzes the reaction: H2O2 + 2H+ -> 2H2O
Catalase
In a figure/graph, which line best depicts a psychtroph incubated at 0°C?
The line that is gradually increasing
A media that has a pH indicator and a high salt concentration can likely _____ the growth of most bacteria.
inhibit
Which is NOT a direct measurement of microbial growth?
Turbidity
Which one is a complex medium?
Tryptone Soy Agar
A sample of ocean water is tested for its bacterial content in a plate count assay. A one-milliliter sample of the water is diluted in a 1:10 dilution series. 0.1 milliliter of the second dilution tube is plated in a pour plate. After incubation, the plate has 191 colonies, indicating that the original water sample contained
191000
If 100 colonies are on a 1:1000 dilution plate, how many bacteria/mL were in the original sample?
100,000
For which of the following types of microbes would a microbiologist employ living host cells to support their growth?
obligate intracellular organisms, such as chlamydias, rickettsias, and viruses
Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched?
thermophile – growth at 37°C
Which of the following statements accurately describes the culture medium necessary for growing an obligate anaerobe, such as Clostridium tetani?
Reducing media are complex media containing chemicals, such as thioglycolate, that combine with oxygen, creating an anaerobic environment.
Which medium (or media) would an autotroph grow but a heterotroph could not?
NaHCO3
Bacteria that can grow in the presence or absence of oxygen (O2) are called __________.
facultative anaerobes
An isolated colony on a streak plate contains millions (or even billions) of identical cells all arising from one initial cell.
True
Which biosafety level (BSL) is appropriate for handling organisms that present a moderate risk of infection?
BSL-2
Microbes have very narrow optimum temperature ranges. Which of the following classifications of microbes are most likely to cause human disease, based on their temperature requirements?
mesophiles
Which of the following phases of the bacterial growth curve is matched with the correct definition?
log phase--the phase in which organisms are actively dividing and the generation time is constant
The chemical requirements for microbial growth include carbon, nitrogen, phosphorus, and sulfur. Why do all cells need nitrogen?
for building amino acids, proteins, and nucleic acids
which line best depicts an obligate anaerobe in the presence of O2?
No growth line
Which of the following statements regarding infections involving biofilms is FALSE?
There is no way to prevent biofilms from developing on surfaces.
Salts and sugars work to preserve foods by creating a
hypertonic environment
Which of the following methods used to count microbes is correctly identified as direct or indirect?
filtration--direct method
Three cells with generation times of 60 minutes are inoculated into a culture medium. Assuming no lag phase takes place, how many cells are there after 5 hours?
96
Which process is best for the short-term storage of bacterial cultures?
refrigeration
Which of the following is an advantage of the direct microscopic count?
requires no incubation time
Assume you inoculated 100 facultatively anaerobic cells onto nutrient agar and incubated the plate aerobically. You then inoculated 100 cells of the same species onto nutrient agar and incubated the second plate anaerobically. After incubation for 24 hours, you should have
the same number of colonies on both plates
The term trace elements refers to
small mineral requirements.
Which one of the following temperatures would most likely kill a mesophile?
60°C
Which of the following is not a characteristic of biofilms?
iron deficiency
Which of the following types of media would not be used to culture aerobes?
reducing media
An organism that has peroxidase and superoxide dismutase but lacks catalase is most likely an
aerotolerant anaerobe
The process of destroying pathogenic microorganisms from skin or living tissue is called?
Antisepsis
Which phase of the Microbial Growth Curve represents a period when the number of viable cells remains relatively constant?
Stationary phase
What are examples of chemical agents that can influence microbial death?
Disinfectants, heavy metals, and solvents
If a population of 1 million bacteria is treated with an antimicrobial chemical, and after 3 minutes only 1,000 bacteria are left alive, what percentage of the population was killed per minute?
99%
How does the death rate of bacteria change as the treatment time increases?
Remains constant
Which phase of the bacterial growth curve would be affected by an antimicrobial treatment that rapidly kills the majority of the population?
Log phase
What factor could influence the effectiveness of antimicrobial chemicals on bacterial populations?
The presence of biofilms
If you have 1,000,000 cells, how many survivors would there be after x minutes ( what formula to use?)
90% die every minute
Which one is the best example of sanitization?
Restaurant uses dishwasher with hot water and soap to treat plates and utensils
Which is the best example of commercial sterilization?
Canned food is treated with heat before being preserved in a can
Which is the best example of disinfectant?
The teacher wipes down each desk with a Clorox wipe
What is the best example of sterilization?
The surgical tech treats each surgical instrument thoroughly for surgery use
What is the best example of degerming?
The new mom asks everyone to wash their hands thoroughly before holding the newborn
What is the best example of antisepsis?
An aseptic solution is applied to a wound before being bandaged up
A suspension of 10^6 Bacillus cereus endospores was put into hot air oven at 170 degrees Celsius. Plate count were used to determine the number of endosporees surviving at the time intervals shown. In a given figure/graph, what is the thermal death time? For 106 Bacillus cereus it is 60
10 minutes
In a particular liquid culture, 100% of the microbes are killed by 12 minutes at 30 degrees Celsius. This is called...
Steam Sterilization
Which treatment is the most effective at controlling microbial growth?
Dry Heat/ Direct Flame
Which of the following disinfectants from a given list by disrupting the plasma membrane?
Phenolics
How does osmotic pressure provide microbial growth control?
Higher osmotic pressure causes dehydration
Which chemical method disrupts the plasma membrane?
Bisphenol
Which chemical method disrupts the proteins of the microbe?
Halogens
Which chemical method disrupts the DNA?
Alcohol
Describe binary fission
A method of asexual reproduction in which a single cell divides into two genetically identical daughter cells.
What do the macronutrients CHONPS stand for?
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur
Why is CHONPS needed for the cell?
Carbon -Backbone of DNA Hydrogen- Maintains structure (part of water) Oxygen- breathing Nitrogen-Builds proteins for DNA Phosphorus- DNA Sulfur- helps form amino acids
What does catalase do?
Breaks down Hydrogen Peroxide (turns it into water and oxygen)
What is the importance of hydrogen peroxide?
antimicrobial agent, sterilization, used for detection of microbes, byproduct of cellular metabolism
What is the importance of peroxidase?
Protects cells against hydrogen peroxide
What is the importance of superoxide radicals?
Defender of the cell from invaders but can still be harmful to the cell
What is the importance of superoxide dismutase?
Protects cells from superoxide radicals
Match each method to whether or not it is a direct or indirect method
Direct microscopic count = Direct The plate count method = Direct Turbidity estimation of bacterial numbers = Indirect Determination of dry weight of cells = Indirect
Match each method to whether or not it is a direct or indirect method
Electronic enumeration of cell numbers = Direct The plate count method = Direct Determination of nitrogen content. = Indirect None = None
By deep-freezing, bacteria can be stored without harm for extended periods. Why do refrigeration and freezing preserve foods?
Slows the growth rate of bacteria which will stop the food from spoiling
A pastry chef accidentally inoculated a cream pie with six S. aureus cells. If S. aureus has a generation time of 60 minutes, how many cells would be in the cream pie after 7 hours?
768
Nitrogen and phosphorus added to beaches following an oil spill encourage the growth of natural oil-degrading bacteria. Explain why the bacteria do not grow if nitrogen and phosphorus are not added.
Nitrogen and Phosphorus are needed for bacteria to grow especially because of the oil spill
Which of the lines best depicts the log phase of a thermophile incubated at room temperature?
The line that is the highest
Which of the lines best depicts the log phase of Listeria monocytogenes growing in a human?
Bottom line
Which of the following does not kill endospores?
pasteurization
Which of the following is most effective for sterilizing mattresses and plastic Petri dishes?
ethylene oxide
Which of these disinfectants does not act by disrupting the plasma membrane?
halogens
Which of the following cannot be used to sterilize a heat-labile solution stored in a plastic container?
autoclaving
Which of the following is used to control microbial growth in foods?
organic acids
Which of the following is not a characteristic of quaternary ammonium compounds?
sporicidal
A classmate is trying to determine how a disinfectant might kill cells. You observed that when he spilled the disinfectant in your reduced litmus milk, the litmus turned blue again. You suggest to your classmate that
the disinfectant might oxidize molecules
Which of the following is most likely to be bactericidal?
ionizing radiation
Gluteraldehyde is among the most effective chemical control agents because it __________.
is considered a relatively safe sterilizing agent
Prior to drawing blood for a blood donation, the nurse will clean the arm with a Betadine solution. This form of antimicrobial control is called __________.
antisepsis
Consider various effects of moist and dry heat to control microbial growth. Which of the following methods would best reduce the number of microbes without altering the taste and chemical composition of beer?
pasteurization
When microbial control methods are used, microbes are destroyed at a constant rate; there is no instantaneous death of all the microbes present. That microbial death rate is influenced by all of the following factors EXCEPT __________.
toxins produced by the microbe
Microbial control methods usually target any of the following cellular components EXCEPT which one?
mitochondria
Contaminated hospital equipment represents a difficult environment to control harmful microbial growth. Regarding influences that affect disinfection of hospital equipment, which of the following is an accurate statement?
The cell walls of gram-negative bacteria are especially resistant to many chemicals that are used destroy microbes.
An agent used to reduce the number of bacteria on a toilet would most accurately be called a(n)
disinfectant
Each of the following chemicals is paired with an item that it can be used on for disinfection or antisepsis purposes. Which one is mismatched?
Chlorhexidine; disinfection of stethoscopes and blood pressure cuffs
This graph shows a microbial death curve for a bacterial population subjected to a heat treatment. Treatment began at time zero. About how many cells were still living after 4 minutes of treatment?
1000 cells
An antimicrobial chemical was added to a population of bacteria. The initial population was 107 living cells (10,000,000). After 2 minutes, only 106 cells still remained alive. After another 2 minutes (4 minutes of total treatment), about how many cells would still be alive?
10^5
Which of the following best describes why microbial death curves are typically plotted logarithmically?
Most of the cell death occurs early in the treatment.
All of the following factors contribute to hospital-acquired infections EXCEPT
None of the answers is correct; all of these factors may contribute to hospital-acquired infection.
Surface-active agents act by decreasing surface tension so that microbes can more easily be removed. All of the following agents use this mechanism of action EXCEPT __________.
halogens
lyophilization
desiccation
Which of the following correctly lists, in increasing order, the resistance of microorganisms to chemical biocides?
Gram-positive bacteria, fungi, endospores, prions
The following data were obtained by incubating gram-positive bacteria in nutrient medium + disinfectant for 24 hours, then transferring one loopful to nutrient medium (subculturing). (+ = growth; - = no growth)
The answer cannot be determined based on the information provided.
Which of the following physical methods of microbial control denatures proteins as a mechanism of action?
boiling or autoclaving
Repeating sequences of noncoding DNA that are used in forensic analysis is called
Short Tandem Repeat Analysis
The antibiotic chloramphenicol binds the 50S large subunit of a ribosome. From this information, you can conclude that chloramphenicol
Prevents translation in prokaryotes
Which are examples of horizontal gene transfer?
Conjugation, transformation, and transduction
How is DNA transferred into transformation from donor to recipient cell?
The recipient grabs the DNA from the donor and integrates it into its own DNA which may give the recipient new abilities
if tryptophan is present, the repressible operon is
affected by the presence of tryptophan is the trp operon.
How do you identify auxotrophs?
From how they grow (they can only grow in a nutrient agar) (So look for a complex agar such as beef broth)
if you have HFr, Trp+ cell that recombines with an F-, Trp-cell, what might happen to the F-, Trp- cell (what traits could it acquire?)
Acquire the ability to synthesize tryptophan
if you have F+, Cys+ cell recombines with an F-, Cys-cell, what might happen to the F-, Cys- cell (what traits could it acquire?)
acquire the ability to produce its own cysteine
What are the products of semiconservative replication for a double-stranded DNA molecule?
Two double-stranded DNA molecules, each consisting of one parental strand and one daughter strand.
Why is DNA replication essential for a cell?
An organism must copy its DNA to pass genetic information to its offspring.
What is the function of the parental DNA in replication?
It serves as the template for DNA replication.
Transcription produces which of the following?
mRNA, tRNA, and rRNA are all produced by transcription.
which of the following makes mRNA from the information stored in a DNA template?
RNA polymerase
Ribosomes contain which of the following?
rRNA
Which of the following is involved in bringing amino acids to the ribosomes?
tRNA
What results from the process of translation?
A polypeptide
How is bacterial translation different from eukaryotic translation?
Bacteria can begin translation before transcription has terminated.
Ribosomes move along the mRNA in which direction?
5’ to 3’
Which of the following genetic elements is transcribed into a single mRNA?
The structural genes
Which operons are always transcribed unless deactivated
Repressible operons
Which operons are never transcribed unless activated?
Inducible operons
where on the DNA strand does a repressor bind?
The operator
A recombinant cell....
is a cell that receives DNA from an outside source and incorporates it into its own.
What is the hallmark of all horizontal gene transfers?
Transfer of DNA between organisms of the same generation
Which of the following is an example of horizontal gene transfer in bacteria?
Transduction, conjugation, and transformation
What is the process of protein synthesis specifically The Central Dogma?
DNA, mRNA, Protein
Operons are made of two or more genes that are located near each other in a sequence of DNA. Some operons allow for regulation of the expression of proteins at the transcriptional level. As a result, some operons are inducible, while others are repressible. Which of the following represents an inducible operon?
the production of enzymes that allow for the fermentation of the sugar lactose when it becomes available in the culture medium
When lactose is not present, the genes to catabolize it are neither transcribed nor translated, so therefore, no proteins are made. Given what you know about bacterial cells and the environments that they grow in, why wouldn’t a bacterium express the lactose catabolism genes all of the time?
It would waste energy and resources to express lactose catabolism genes all of the time (constitutively) because lactose is not always preferred.
One of the benefits of performing genetic experiments is to better understand microbial processes. Which of the following scenarios is NOT an application for microbial genetics?
Grocery stores are now selling fruits that have been irradiated to prevent the growth of fungi.
Which of the following enzymes unwinds the two strands of DNA so that they can be copied during replication?
helicase
Which of the following is a DNA strand complementary to CGA ATC AGC?
GCT TAG TCG
Which of the following statements concerning transcription is true?
All types of RNA in the cell are synthesized by transcription, which uses a portion of DNA as a template for copying.
Which of the following best describes the flow of information in cells?
mRNA is made by copying specific regions of DNA called genes. Ribosomes use mRNA as instructions, which provide a code specifying the order of amino acids in a protein.
Which of the following statements concerning sugar utilization in E. coli is true?
Bacteria growing on glucose as the sole carbon source grow faster than on lactose.
Which of the following does NOT accurately apply to the Ames test?
The Ames test is based on the observation that reversions CANNOT occur in mutant bacteria.
Deleting or inserting one nucleotide pair in the middle of a gene is an example of which of the following?
frameshift mutation
Which of the following is a method of vertical gene transmission?
cell division
Frederick Griffith did experiments on genetic transformation. Which of the following statements about his experiments is accurate?
Griffith found that a soluble substance (referred to as the "transforming principle") released from dead (virulent) bacteria entered live (avirulent) bacteria and changed them genetically, causing them to become virulent. We now know that this "transforming principle" is DNA.
Which statement regarding genes and evolution is true?
Random, heritable genetic mutations are a source of genetic variation. This variation is necessary for natural selection to occur.
When two genes from two different people are sequenced and aligned, it is discovered that there are multiple sequence differences in the coding segment DNA level. However, when the proteins formed by the genes have their amino acids sequenced, there is no difference observed between the two. What is the most likely explanation for this observation?
The mutations lie at locations where they don't affect protein sequence due to degeneracy of the genetic code.
The necessary ingredients for DNA synthesis can be mixed together in a test tube. The DNA polymerase is from Thermus aquaticus, and the template is from a human cell. The DNA synthesized would be most similar to
human DNA.
Synthesis of a repressible enzyme is stopped by the
corepressor-repressor complex binding to the operator.
Assume the two E. coli strains shown below are allowed to conjugate. Hfr: pro+, arg+, his+, lys+, met+, ampicillin-sensitive F-: pro-, arg-, his-, lys-, met-, ampicillin-resistant What supplements would you add to glucose minimal salts agar to select for a new recombinant cell that is lys+, arg+, amp-resistant?
ampicillin, proline, histidine, methionine
Match
A mutagen that is incorporated into DNA in place of a normal base = Nucleoside analog A mutagen that causes the formation of highly reactive ions = Ionizing radiation A mutagen that alters adenine so that it base-pairs with cytosine = Base-pair mutagen
Match
A mutagen that causes insertions = Frameshift mutagen
= A mutagen that causes the formation of pyrimidine dimers = Nonionizing radiation
Describe transduction
Transfer of DNA from a donor to a recipient cell by a bacteriophage.
Describe Transformation
Transfer of DNA from a donor to a recipient as naked DNA in solution.
Feedback inhibition differs from repression because feedback inhibition
stops the action of preexisting enzymes.
Bacteria can acquire antibiotic resistance by all of the following except
snRNPs
Suppose you inoculate three flasks of minimal salts broth with E. coli. Flask A contains glucose. Flask B contains glucose and lactose. Flask C contains lactose. After a few hours of incubation, you test the flasks for the presence of β-galactosidase. Which flask(s) do you predict will have this enzyme?
Flask C (the one with lactose)
Plasmids differ from transposons in that plasmids
are self-replicated outside the chromosome.
Describe catabolite repression
Mechanism by which the presence of glucose inhibits the lac operon.
Describe induction
The mechanism by which lactose controls the lac operon.
Two offspring cells are most likely to inherit which one of the following from the parent cell?
a change in a nucleotide in DNA
Which of the following is not a method of horizontal gene transfer?
binary fission
What does a vector, like PUC19 contain in order to easily take an insert and transform a cell?
Vectors like pUC19 contain essential elements for replication, selection, and manipulation of the inserted DNA.
Advantages of a viral vector over plasmid vector is
Accept larger pieces of foreign DNA, Can be cloned in the virus host cells
Describe the key features of a restriction enzyme
Recognizes and cut only one particular sequence of nucleotide bases in DNA through recognition, Protect bacterial cells by hydrolyzing phage DNA
Place the steps of constructing a genomic library in order (A collection of cloned DNA fragments created by inserting restriction enzyme fragments in a bacterium, yeast, or phage.)
- Isolate DNA from the organism
- Use a restriction enzyme on the DNA and the vector
- Use ligase on the DNA and the vector
- Transform host bacteria
- Culture bacteria on a plate containing antibiotics
- Use reverse transcriptase on the mRNA and the vector
Explain how DNA replication and PCR are similar
DNA occurs naturally while PCR occurs in a lab
How is cDNA made?
cDNA (short for copy DNA; also called complementary DNA) is synthetic DNA that has been transcribed from a specific mRNA through a reaction using the enzyme reverse transcriptase.
How can genomes from microbes that are not able to grow in the lab still be studied?
Even if microbes can't be grown in a lab, their DNA can still be studied using a method called metagenomics.
Which technology uses DNA probes to detect DNA fragments?
Southern Blotting
Foreign DNA can be inserted into cells using a variety of different methods. Which method involves the formation of microscopic pores in the cell's membrane?
electroporation
The use of "suicide" genes in genetically modified organisms is designed to
prevent the growth of the modified organisms in the environment.
The field of proteomics concerns itself with
determining all of the proteins expressed by a cell.
Which of the following best describes a clone in the context of genetic modification procedures?
a culture of genetically identical cells
Which of the following best describes why a vector is used in genetic modification procedures?
Cells usually won’t copy an isolated gene sequence.
Recombinant DNA techniques typically involve generating a clone. Why?
Producing a clone generates many copies of the gene of interest.
Which of the following best describes how recombinant DNA technology currently helps patients who do NOT produce adequate amounts of growth hormone (hGH)—a condition that otherwise leads to stunted growth?
Bacteria now produce hGH.
Which of the following is NOT a property of useful vectors?
They always contain only one gene.
Which of the following statements about recombinant DNA technology is FALSE?
It has limited application because genes of interest cannot be moved from one type of cell to another.
Why is baker's yeast useful for expressing genetically engineered genes?
Yeast cells are eukaryotic and so would likely be successful in expressing eukaryotic genes.
The most important property of a DNA vector is
its ability to replicate within the cell.
Which of the following applications of recombinant DNA technology is NOT controversial?
metagenomics
Which of the following pairings of recombinant DNA techniques and applications does NOT match?
Gene silencing; production of subunit vaccines
What is the end goal of PCR?
To quickly increase the number of copies of a specific DNA sequence
PCR stands for
polymerase chain reaction.
Which of the following is an application that uses PCR?
Sequencing a gene, diagnosing a disease, and providing enough DNA for cloning into another organism
Which enzyme would cut this strand of DNA? GCATGGATCCCAATGC
Enzyme Recognition BamHI G↓GATCC CCCTAG↑G
Scientists like to use fluorescent proteins for various types of recombinant DNA procedures. You have a very small amount of the gene for a fluorescent protein. You'd like to make a fluorescent bacterium. Which of the following represents the correct sequence of procedures that you would use?
Amplify the gene using PCR. Insert the gene into a plasmid vector. Transform the vector into the bacteria.
PCR can be used to identify an unknown bacterium because
the DNA primer is specific to particular target DNA sequences
Which of the following methods could be used to identify the source of an outbreak?
DNA fingerprinting
How do restriction enzymes cut DNA sequences
They cut DNA at sites, called recognition sites, that have specific nucleotide sequences
In general, how might recombinant DNA technology be used to prevent a genetic disorder caused by a mutation in a single gene?
To insert a desirable gene, remove an undesirable gene, or replace a defective gene with a functioning gene
Which of the following attaches the target gene to a desired location?
DNA ligase
Why would a recombinant DNA molecule be inserted into a host cell?
It can be copied, transcribed, and translated into a desired protein.
Which statement regarding agricultural biotechnology is FALSE?
Agricultural biotechnology is extremely limited because foreign genes cannot be inserted into plant cells.
Self-replicating DNA used to transmit a gene from one organism to another is a
vector
Which statement best describes restriction enzymes?
They are important for cloning applications because they can be used to cut DNA at specific nucleotide sequences.
What is the function of the primers in PCR?
They provide a 3’ end for the DNA polymerase.
In which direction does DNA polymerase synthesize the new DNA strand?
5’ to 3’
What provides the energy for DNA polymerization in a PCR reaction?
Deoxyribonucleoside triphosphates
Why is DNA polymerase from Thermus aquaticus ideal for PCR?
It can withstand the high temperatures associated with PCR
Restriction enzymes were first discovered with the observation that
phage DNA is destroyed in a host cell.
The DNA probe, 3’-GGCTTA, will hybridize with which of the following?
5’-CCGAAT
Which of the following is the fourth basic step to genetically modify a cell?
ligation
The following enzymes are used to make cDNA. What is the second enzyme used to make cDNA?
ribozyme
If you put a gene in a virus, the next step in genetic modification would be
transduction.
You have a small gene that you want replicated by PCR. You add radioactively labeled nucleotides to the PCR thermal cycler. After three replication cycles, what percentage of the DNA single strands are radioactively labeled?
87.5%
Define Library
Pieces of human DNA stored in yeast cells.
Describe a clone
A population of cells carrying a desired plasmid.
Describe a vector
Self-replicating DNA for transmitting a gene from one organism to another.
Describe antisense
DNA that hybridizes with mRNA.
A prokaryotic cell hitched a ride to Earth on a space shuttle from some unknown planet. The organism is a psychrophile, an obligate halophile, and an obligate aerobe. Based on the characteristics of the microbe, describe the planet.
Cold, salty, aerobic
Which of the following criteria is most useful in determining whether two organisms are related?
Both are gram-positive.
If you Gram-stained the bacteria that live in the human intestine, you would expect to find mostly
gram-negative rods
Which stain (from a list) would be helpful in determining the size and shape of a colorless bacterium WITHOUT fixing.
India Ink or Nigrosin stain
If you were preparing nutrient agar at home and did not have an autoclave, what could you use to sterilize the nutrient agar?
pressure cooker at 121°C for 15 minutes
If you knew the sequence of nucleotides within a gene, which one of the following could you determine with the most accuracy?
the primary structure of the protein
Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage, such as through the urethra and into the urinary bladder) are susceptible to infections because
biofilms develop on catheters.
A suspension of 106 Bacillus cereus endospores was put in a hot-air oven at 170°C. Plate counts were used to determine the number of endospores surviving at the time intervals shown.
The answer cannot be determined based on the information provided
Most fungi grow best at pH
5
Which of the following is NOT a characteristic of B cells?
They recognize antigens associated with MHC I.
Study Notes
Binary Fission: A Fundamental Aspect of Prokaryotic Reproduction
- Binary fission is a form of asexual reproduction used by prokaryotes, such as bacteria, where one parent cell divides into two identical daughter cells.
- Each daughter cell receives a complete set of genetic instructions, ensuring the continuation of the species' traits.
- Binary fission is a clonal method of reproduction, meaning the offspring are genetically identical to the parent.
DNA Replication and Segregation
- Before cell division, DNA replication occurs, producing two identical sets of genetic material.
- The duplicated DNA is distributed equally between the two daughter cells, ensuring each cell receives a complete set of genetic information.
Cell Division and Asexual Reproduction
- Binary fission is a crucial aspect of prokaryotic cell division, enabling rapid population growth and adaptation to environmental changes.
- Asexual reproduction allows for the creation of offspring without the fusion of gametes, ensuring the genetic information remains intact.
Prokaryotic Cells and Binary Fission
- Prokaryotic cells, such as bacteria, have unique characteristics that enable efficient binary fission:
- Circular chromosomes allow for continuous division without issues related to telomeres.
- Small genome size enables efficient replication and adaptation to changing conditions.
- Rigid cell walls preserve cell shape during cell division.
- Compartmentalization of organelles prevents mixing of organelles between mother and daughter cells.
Variants of Binary Fission
- Some bacteria engage in variations of binary fission, such as:
- Multiple offspring production: producing multiple daughter cells rather than just two.
- Budding: forming a protrusion from the surface, which eventually detaches as a new cell.
Importance of Binary Fission
- Binary fission plays a pivotal role in the asexual reproduction of prokaryotic organisms, particularly bacteria.
- Understanding binary fission provides insights into fundamental aspects of life and has potential applications in fields like synthetic biology and medicine.
Microbial Death and Control
- Disinfection, sterilization, antisepsis, and sanitization are methods used to destroy or reduce pathogenic microorganisms:
- Disinfection: reducing the number of pathogens on non-living surfaces.
- Sterilization: eliminating all forms of life from surfaces and objects.
- Antisepsis: destroying or inhibiting the growth of microorganisms on living tissue.
- Sanitization: reducing pathogens to levels considered safe by public health standards.
Microbial Growth Curve
- The Microbial Growth Curve represents the changes in the number of viable cells over time under specific conditions:
- Four main phases: lag phase, logarithmic growth phase, stationary phase, and death phase.
Factors Influencing Microbial Death
- Physical, chemical, and biological agents can influence microbial death:
- Temperature, light, and nutrient levels affect bacteria.
- Chemical agents include disinfectants, heavy metals, and solvents.
- Biological agents encompass viruses, bacteriophages, and parasites.
Applications of Microbial Death
-
Understanding microbial death is crucial in various fields, including biology, medicine, agriculture, and environmental science.
-
It helps develop strategies to control microbial populations, prevent diseases, improve food production, and protect ecosystems.### Investigating Cell Death Processes
-
Researchers expose cells to varying concentrations of a potential cytotoxic drug to investigate cell death processes.
-
Microscopy techniques, flow cytometry, and biochemical assays are used to quantify the resulting effects.
-
These methods enable monitoring of cell viability, apoptosis, necrosis, and autophagy under different treatment conditions.
Cell Survival Calculations
- Cell survival calculations are crucial for understanding how cells respond to environmental stressors.
- By determining the concentration of a substance needed to cause significant cell death, researchers can estimate its therapeutic index and potential efficacy as a treatment option.
- Survival curves help establish optimal conditions for culturing cells in vitro.
Importance of Cell Survival Calculations
- Cell survival calculations are essential tools for studying cell death processes.
- They enable researchers to assess the impact of various stressors on cell function and survival.
- These calculations contribute to our understanding of cellular responses to stress and the development of novel therapies based on these responses.
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