bio 102 unit 3 cumulative practice
Fruit flies normally produce two types of antimicrobial peptides (defensin and drosomycin). Mutant fruit flies were generated that produced no antimicrobial peptides, defensin only, or drosomycin only. Wild-type flies and the mutant flies were then tested for survival after infection with Micrococcus luteus bacteria. What statement about these data is true?
After five days, greater than 90% of mutant fruit flies are dead.
A new pathogenic form of influenza A can emerge when __________. there is a concurrent infection of a pig or bird by two or more different strains of influenza A the genomes of two or more influenza A strains mix and match during viral assembly within a host a mutation occurs in a virus as it passes from one host to another All of choices are correct. a virus with a novel genetic makeup recombines with viruses that circulate widely among humans
All of choices are correct.
Emerging viruses can originate from which of the following sources? animal viruses the mutation of existing human viruses viruses previously confined to small, isolated populations that can now spread due to technological or social changes such as the development of affordable international travel All of the choices are correct. None of the choices is correct.
All of the choices are correct.
HIV is a dangerous pathogen because __________. the virus prevents recognition and elimination by the immune system the virus evolves within the body it leads to the loss of T cells it mutates at a very high rate All of the choices are correct.
All of the choices are correct.
The symptoms of a viral infection in a person can be caused by __________. toxic viral components, such as envelope proteins the death of infected cells the reaction of the individual's immune system to the infection the production of toxins by infected cells All of the choices are correct.
All of the choices are correct.
Which is an example of vertical transmission of a virus in plants?
An infected plant produces seeds that contain the virus, giving rise to infected progeny. Vertical transmission refers to the spread of a virus from parent to offspring.
Which of the following events occurs first when a wound that breaks the skin has occurred?
Platelets release proteins that form clots and decrease bleeding. (the first response to broken skin is the release of clotting proteins from platelets in the bloodstream, which decreases bleeding and helps to seal the wound.)
How do prions, which are misfolded proteins, infect organisms?
Prions enter brain cells and cause normal forms of the protein to refold into the prion form.
Which statement about prokaryotes is true?
Prokaryotes are widely used for bioremediation. Prokaryotes have been used in sewage treatment for decades, and they are being used to clean up oil spills and radioactive waste.
Why is salt a good preservative to use for foods such as pork and fish?
Prokaryotic cells living in the food will shrink from their cell walls, impacting their ability to reproduce.
Which statement about the genomes of prokaryotes is correct?
Prokaryotic genomes are composed of circular DNA.
Which of the following nucleic acids make(s) up viral genomes?
DNA or RNA
Fruit flies normally produce two types of antimicrobial peptides (defensin and drosomycin). Mutant fruit flies were generated that produced no antimicrobial peptides, defensin only, or drosomycin only. Wild-type flies and the mutant flies were then tested for survival after infection with Neurospora crassa fungi. What statement about these data is true?
Drosomycin protects fruit flies from N. crassa infections to a higher degree than does defensin.
What is the origin of the phospholipid membrane that envelops many animal viruses?
It is "stolen" from the host cell, but it contains some proteins encoded by the viral genome. Newly formed viruses "cloak" themselves in phospholipid membrane derived from the host, but certain components encoded by the viral genome are also included in the envelope.
True or false? The leukocytes of the innate immune system are B cells, macrophages, and neutrophils.
False, the leukocytes of the innate immune system are mast cells, macrophages, and neutrophils.
Which statement about cholera is true?
Its symptoms are caused by an exotoxin that stimulates intestinal cells to release chloride ions into the gut.
Currently scientists think the early atmosphere probably consisted of __________.
N2, H2O, CO2, NH3, CH4, H2, and H2S
Which is an immediate function of histamine?
Nearby blood vessels dilate, becoming more permeable and resulting in an increase of the local blood supply. This causes redness and an increase in temperature.
What can a virus do without a host cell? produce nucleotides for use in replication and transcription transcribe DNA produce ATP for energy synthesize proteins None of the choices is correct.
None of the choices is correct. Viruses are obligate intracellular parasites. They require a host cell to carry out all of the above cellular processes (and more).
Research suggests that the first self-replicating molecules were __________.
RNA RNA molecules are important catalysts in modern cells. Some RNA is autocatalytic, and in the prebiotic world, long before there were enzymes or DNA, RNA molecules may have been fully capable of self-replication
Why do some scientists believe that RNA, rather than DNA, was the first genetic material?
RNA has both information storage and catalytic properties.
Reverse transcription, carried out by retroviruses, is the process by which __________.
RNA information is copied into DNA Retroviruses are equipped with an enzyme called reverse transcriptase, which makes a DNA copy of an RNA template, providing information flow from RNA to DNA.
Suppose a B cell is unable to perform alternative splicing. What consequence will this have in regards to the immune response of the B cell?
The B cell will make a limited number of antigen receptors.
Salmonella are a genus of pathogenic bacteria that can cause infections through the gastrointestinal tract. How could Salmonella poisoning be initiated if a human were to ingest these bacteria?
The bacteria survive the acidic environment of the stomach and resist lysosomal degradation in macrophages.
Two prokaryotes are shown in the figure that have additional cellular membranes within the plasma membrane. What functions could the respiratory membranes and the thylakoid membranes provide?
The respiratory membrane allows a functional electron transport chain and oxidative phosphorylation of ATP.
Which of the following responses correctly lists the order of events in a generalized viral replicative cycle?
The virus enters the cell, host enzymes replicate the viral genome, enzymes transcribe the viral genome into mRNA.
A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?
The plants would develop the typical symptoms of TMV infection.
Which of the following statements correctly describes one difference between vertical and horizontal transmission of plant viruses?
Vertical transmission is transmission of a virus from a parent plant to its progeny horizontal transmission is one plant spreading the virus to another plant.
Most molecular biologists think that viruses originated from naked bits of cellular nucleic acid. Which of the following observations supports this theory?
Viral genomes are usually similar to the genome of the host cell.
In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA, referred to as the Baltimore requirements. The table below shows the results of testing five viruses (A−−E) for nuclease sensitivity, the ability of the viral genome to act as an mRNA, and the presence (+) or absence (-) of each virus's own polymerase.
a
Which statement describes what would most likely happen to microbes in the blood?
They are phagocytosed by macrophages in the spleen, (Microbes are trapped in the netlike architecture of the spleen and then are attacked by macrophages)
Which of the following statements accurately describes plant virus infections?
They are spread via the plasmodesmata.
What do macrophages and neutrophils have in common?
They are the two types of phagocytic cells in the mammalian body, (Neutrophils are phagocytic cells that constitute 60-70% of all white blood cells. Macrophages, which develop from monocytes, are long-lived phagocytes)
What is true about R plasmids?
They can be transferred from one bacterium to another via conjugation. They can carry several resistance genes. (2 and 3 choices correct)
How do retroviruses, such as HIV, differ from other viruses?
They can transcribe a DNA copy from an RNA template. Retroviruses contain the enzyme reverse transcriptase, which transcribes DNA from an RNA template, which is opposite of the usual direction of information flow.
Which of the following statements correctly describes viruses?
They cannot reproduce without a host cell.
What is the role of heterocysts in a cyanobacterial filament?
They carry out nitrogen fixation. Filaments are colonies of prokaryotic cells. In some cases, photosynthesis and nitrogen fixation cannot occur in a single cell because oxygen inactivates enzymes needed for nitrogen fixation. Heterocysts are specialized cells that carry out nitrogen fixation.
Which of the following statements correctly describes adenoviruses?
They contain DNA surrounded by a capsid.
Which of the following statements best describes the role of mast cells in the inflammatory response?
They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream. (Mast cells release chemicals that dilate nearby capillaries, increasing their permeability and allowing blood components to enter the region from the bloodstream, thus causing localized swelling.)
Why are retroviruses considered a special class of viruses?
They transcribe RNA to DNA using reverse transcriptase, (Retroviruses reverse the normal flow of information, forming a DNA provirus from an RNA genome.)
Why are retroviruses considered a special class of viruses?
They transcribe RNA to DNA using reverse transcriptase.
Viruses that infect bacteria are called __________.
bacteriophages
Please use the following information to answer the question below. Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O2 reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O2. Consider the colonial aquatic cyanobacterium Anabaena, whose heterocytes are described as having "a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates." Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
be obligate anaerobes and package these enzymes in specialized cells or compartments that inhibit oxygen entry
Please use the following information to answer the question below. Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O2 reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O2. Consider the colonial aquatic cyanobacterium Anabaena, whose heterocytes are described as having "a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates." Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
be obligate anaerobes and package these enzymes in specialized cells or compartments that inhibit oxygen entry
Once you have been exposed to an antigen, you develop immunity against the same antigen because __________.
certain lymphocytes enable the rapid formation of the proper antibodies These lymphocytes are called memory cells. On later exposure to the antigen, a rapid response occurs and effector cells are quickly produced.
Innate immunity and adaptive immunity are both _____.
characteristics of all vertebrate animals
Innate immunity and adaptive immunity are both _____.
characteristics of all vertebrate animals (Only vertebrate animals have fully developed adaptive immunity to supplement their innate immunity)
Thiobacillus ferrooxidans is a type of bacteria that oxidizes iron compounds for energy and then uses that energy to build carbohydrates. We might best recognize this bacterium as the rust-colored ring that builds up inside toilet bowls. Thiobacillus ferrooxidans is an example of a
chemoautotroph
Which of the following describes an organism that oxidizes inorganic substances to obtain energy that is used, in part, to fix CO2 from the atmosphere?
chemoautotrophs
In an experiment, a microbiologist put equal numbers of each of the following organisms into a flask of sterile broth, consisting mostly of sugar and a few amino acids. She then placed the flask in the dark. Which of the organisms would be most likely to survive?
chemoheterotrophic bacteria These organisms do not require light and use organic compounds for both energy and carbon.
Which group of bacteria is unusual in that they lack peptidoglycan in their cell walls?
chlamydias The gram-negative walls of chlamydias are unusual in that they lack peptidoglycan. One species, Chlamydia trachomatis, is the most common cause of blindness in the world.
The proliferation of the B lymphocyte to which a specific antigen binds is referred to as __________.
clonal selection When an antigen binds to a B cell or a T cell, that cell proliferates, forming clones of effector cells with the same specificity.
Bacterial cells, but not eukaryotic cells, possess __________.
a nucleoid with a circular chromosome The bacterial chromosome is one double-stranded DNA molecule in the form of a ring, and is not contained within a nuclear envelope.
The H1N1 2009 outbreak is considered to have been which of the following?
a pandemic
Which of the following is a defining characteristic that all protocells or vesicles had in common?
a surrounding membrane or membrane-like structure
Which statement about cyanobacteria is true? They are the only prokaryotes that perform plantlike, oxygen-producing photosynthesis. It can be said that nitrogen-fixing cyanobacteria are the most self-sufficient of all organisms. Some species may carry on nitrogen fixation. Some are single cells, whereas others live in filamentous colonies. All of the choices are correct.
all
Plasmids __________. are transferred from one bacterium to another by conjugation replicate independently of the main chromosome often contain antibiotic resistance genes allow bacteria to survive adverse conditions All of the choices are correct.
all may also direct the metabolism of rarely encountered nutrients
Which of the three types of viruses shown in the figure above would you expect to include a capsid(s) as part of their overall structure?
all three
An adaptive immune response is initiated by the presence of which molecules?
antigen antigen- a foreign molecule that elicits a specific response by a lymphocyte
New flu shots are needed every year to protect against infection because of __________.
antigenic variation
If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell but does contain the large circular chromosome, the regenerated bacterium will probably also
lack antibiotic-resistant genes.
Macrophages are _____.
large phagocytic cells present throughout the body (they are active phagocytes)
Gram-negative bacteria have __________ peptidoglycan than gram-positive cells, and their cell walls are __________ complex structurally.
less ... more
A phage that inserts itself into the host DNA is called __________.
lysogenic In the lysogenic cycle, the nucleic acid enters the host cell and the phage "ghost" remains outside. The phage DNA forms a circle and is incorporated into the host chromosome as a prophage.
An invertebrate, such as an insect, has innate immunity activity in its intestine that likely includes
lysozyme
The phage reproductive cycle that kills the bacterial host cell is a __________ cycle, and a phage that always reproduces this way is a __________ phage.
lytic ... virulent A lytic cycle ends with the lysis of the bacterial host cell.
RNA viruses require their own supply of certain enzymes because __________.
host cells lack enzymes that can replicate the viral genome
What is part of the inflammatory response?
dilation of the capillaries Histamine triggers the dilation and increased permeability of nearby capillaries; this increased blood flow is what causes redness and fever during an inflammatory response.
Mammals have Toll-like receptors (TLRs) that can recognize a kind of macromolecule that is absent from vertebrates but present in/on certain groups of pathogens, including viral
double-stranded RNA.
Prokaryotes found inhabiting the Great Salt Lake would be __________.
extreme halophiles Extreme halophiles (salt-loving bacteria) live in such places as the Great Salt Lake and the Dead Sea.
Which of the following steps has NOT yet been accomplished by scientists studying the origin of life?
formation of protocells that use DNA to direct the polymerization of amino acids
Which of the following characteristics, structures, or processes is common to both bacteria and viruses?
genetic material composed of nucleic acid
The pointer is indicating the virus's _____. it is circle of dots/smaller circles and in the middle of it are two squiggly lines stacked on top of each other and the arrow is pointing to the lines
genome (its nucleic acid genome)
Which of the following processes can be effective in preventing the onset of viral infection in humans?
getting vaccinated
The body produces antibodies complementary to foreign antigens. The process by which the body comes up with the correct antibodies to a specific invader is most like __________.
going to a shoe store and trying on shoes until you find a pair that fits Unless an immune cell with the appropriate surface receptor exists prior to the infection, no immune response will be possible. Antigens will be presented to a number of lymphocytes, each containing any one of millions of antigen receptors, until a match is found.
Please use the following information to answer the question(s) below. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from bacteriophages and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.What should be true of the cell wall of this bacterium?
got it wrong but we know its NOT : Its innermost layer is composed of a phospholipid bilayer.
The complement system is a
group of antimicrobial proteins that act together in a cascading manner
The complement system is a
group of antimicrobial proteins that act together in a cascading manner.
Vaccines for viral diseases are __________ and help prevent infection by __________.
harmless derivatives of pathogenic viruses ... stimulating the immune system to mount a defense against the actual pathogen
In the figure above, at the arrow marked II, what enzyme is being utilized? (its like a circle off to the side)
host cell DNA polymerase
Inflammatory responses typically include
increased activity of phagocytes in an inflamed area.
Acidity in human sweat is an example of
innate immunity.
Chemicals produced by virus-infected cells that alert neighboring cells to prepare a defense are called __________.
interferons, Interferon is a chemical messenger of the immune system, produced by virus-infected cells and capable of helping other cells resist the infection.
Innate immunity
is activated immediately upon infection.
Which group of prokaryotes is classified as a member of the domain Archaea?
methanogens The three main groups of archaea are the methanogens (methane producers), extreme halophiles (salt lovers), and extreme thermophiles (heat lovers).
Which type of cell is responsible for causing apoptosis in cancer cells and virus-infected cells?
natural killer cells Once natural killer cells are attached to a virus-infected cell or cancer cell, they release chemicals that lead to the programmed death of the cell.
The early atmosphere on Earth is thought to have contained little of which gas?
oxygen
The flu virus H1N1 caused a __________.
pandemic
A type of ecological relationship called __________ involves one organism living at the expense of another organism.
parasitism
Adaptive immunity depends on
pathogen-specific recognition
Adaptive immunity depends on
pathogen-specific recognition.
Bacteria that use light for their energy source and CO2 for their carbon source are called __________.
photoautotrophs Photoautotrophs are photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from carbon dioxide.
Which of the following describes an organism that obtains energy from light?
phototroph only
Plant viruses spread throughout the plant by way of __________.
plasmodesmata
The bacterium that causes tetanus can be killed only by prolonged heating at temperatures considerably above boiling. This suggests that these bacteria __________.
produce endospores are extremely heat resistant.
Alternative RNA splicing
produces multiple proteins from a single coding gene.
The earliest organisms were most likely __________.
prokaryotic
Antibodies are in which class of proteins?
receptor Antibodies are antigen-binding immunoglobulins, produced by B cells, which function as the effector in the immune response. They are soluble receptors specific to particular antigens.
Histamines trigger dilation of nearby blood vessels as well as an increase in vessel permeability, producing
redness, heat, and swelling.
If microorganisms penetrate the innate defenses, an inflammatory response may be initiated by the __________.
release of chemicals such as histamine by mast cells
Which choice below describes a function of white blood cells that helps them carry out defensive functions more effectively?
release of cytokines Cytokines help recruit and activate lymphocytes.
The tertiary structure of a protein
relies on multiple weak bonds between side chains.
A bacterium or other particle taken up by phagocytosis is
routed to lysosomes for degradation.
The lytic cycle of bacteriophage infection ends with the _____.
rupture of the bacterium (the bacterium ruptures and phages are released)
On early Earth, what substance is hypothesized to have played a key role to facilitate the formation of polymers of amino acids, polymers of RNA, and vesicles?
sand, rock, or clay
The first genes on Earth were probably
self-replicating RNA molecules.
The Miller and Urey abiotic synthesis experiment (and subsequent, similar experiments) showed that __________.
simple organic molecules can form spontaneously under conditions like those thought to prevail early in Earth's history In 1953 Stanley Miller created, in the laboratory, conditions thought to be comparable to those of early Earth, with water vapor, hydrogen, methane, and ammonia. The Miller apparatus produced a variety of amino acids and other organic compounds found in living organisms today.
The genetic material of HIV consists of _____. Which of these binds to receptor molecules on the host cell membrane? What is the function of reverse transcriptase? What is the source of a viral envelope? Which of these is reverse transcriptase? Which of these is the viral genome? What enzyme allows a retrovirus to make DNA from an RNA template? Double-stranded viral DNA is incorporated into a host cell as a _____.
single-stranded RNA, (consists of two molecules of single-stranded RNA) A, (glycoproteins on the viral envelope recognize and bind to receptors on the host cell. It catalyzes the formation of DNA from an RNA template. host cell membrane C E, (HIV is an RNA virus) reverse transcriptase, (it catalyzes the formation of this) provirus, ("provirus" is the name given to double-stranded viral DNA that has been incorporated into a host cell's genome)
A type of cell that makes immunizations effective is the __________.
memory B cell The secondary immune response, which is due to memory cells, provides long-term protection after exposure to a pathogen.
Which types of cells initiate a secondary immune response?
memory cells The secondary immune response, which depends on memory cells, provides long-term protection after exposure to a pathogen.
Secondary immune responses upon a second exposure to a pathogen are due to the activation of
memory cells.
Biofilms are an example of __________.
metabolic cooperation among prokaryotic species Bacteria in biofilms send signals to each other, produce structures to channel nutrients in and wastes out, and produce proteins that help the cells adhere to the substrate and to each other.
The cells and signaling molecules that initiate inflammatory responses are
the mast cells and the histamines.
According to scientists' hypotheses, prokaryotes most likely evolved prior to eukaryotes because
the oldest fossilized cells resemble prokaryote
According to scientists' hypotheses, prokaryotes most likely evolved prior to eukaryotes because
the oldest fossilized cells resemble prokaryotes.
Which of the following characteristics determine a virus's host range?
the proteins on its surface and that of the host
The eyes and the respiratory tract are both protected against infections by
the secretion of lysozyme onto their surfaces.
In humans, the first line of defense against infection is __________.
the skin and mucous membranes (provide first-line barriers preventing pathogens from gaining entrance to the body)
Miller and Urey's experiments that attempted to recreate conditions on early Earth were significant because __________.
they showed that organic molecules such as amino acids could be produced from inorganic molecules
Bacterial infection in a previously uninfected house cat would most quickly activate its
toll-like receptors.
Viral DNA makes mRNA by the process of _____.
transcription, (Viral DNA co-opts the cell's reproductive machinery)
Antibodies are made up of
two heavy chains and two light chains.
A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from bacteriophages and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.In which feature(s) should you be able to locate a complete chromosome of this bacterium? 1. nucleolus 2. pili 3. endospore 4. nucleoid
3 and 4
Please use the following information to answer the question(s) below. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from bacteriophages and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.In which feature(s) should you be able to locate a complete chromosome of this bacterium?1. nucleolus2. pili3. endospore4. nucleoid
3 and 4, so the endospore and nucleoid
Approximately how far back in time does the fossil record extend?
3.5 billion years
Earth probably formed __________ years ago, and the first life evolved as early as __________ years ago.
4.5 billion ... 3.9 billion, (Because fossils of bacterial communities have been discovered that are 3.5 billion years old, it is reasonable to assume life originated around 3.9 billion years ago)
In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA, referred to as the Baltimore requirements. The table below shows the results of testing five viruses (A−−E) for nuclease sensitivity, the ability of the viral genome to act as an mRNA, and the presence (+) or absence (-) of each virus's own polymerase. Based on the table above, which virus meets the requirements for a bacteriophage?
A
Based on the table above, which virus meets the requirements for a bacteriophage?
A
Which of the following statements correctly describes one characteristic of the lytic cycle of viral replication?
A large number of phages are released at a time.
In the lysogenic cycle of phages __________. the nucleic acid core of the phage is all that enters the host cell the viral nucleic acid inserts itself into the host chromosome the viral nucleic acid is replicated along with the host DNA only a small number of the viral genes are expressed All of the choices are correct.
All of the choices are correct. In the lysogenic cycle, the phage DNA enters the host cell, forms a circle, and is then incorporated into the host chromosome as a prophage. The prophage replicates with each round of host replication. Under certain conditions, the prophage exits the host chromosome and enters the lytic cycle.
Which may be a component of a virus? single-stranded RNA double-stranded DNA phospholipid bilayer protein All of the choices can be part of a virus.
All of the choices can be part of a virus.
Emerging viruses arise by __________. -mutation of existing viruses -the spread of existing viruses to new host species -the spread of existing viruses more widely within their host species -All of the listed responses are correct.
All of the listed responses are correct.
Emerging viruses arise by __________. mutation of existing viruses the spread of existing viruses to new host species the spread of existing viruses more widely within their host species All of the listed responses are correct.
All of the listed responses are correct.
Why are viruses called obligate intracellular parasites? -All of the listed responses are correct. -They must use a host cell's amino acids to synthesize proteins. -They must use a host cell's nucleotides for transcription and replication. -They must use a host cell's metabolic enzymes and pathways to obtain energy. -They must use a host cell's ribosomes to synthesize proteins.
All of the listed responses are correct.
Which secretion is not a barrier that prevents pathogens from entering the body?
Antigens (are foreign molecules that initiate an immune response)
Which secretion is not a barrier that prevents pathogens from entering the body? True or false? The leukocytes of the innate immune system are B cells, macrophages, and neutrophils. How do cells involved in the innate immune response detect the presence of pathogens? Which of the following cells can engulf a pathogen? Which of the following statements best describes the role of mast cells in the inflammatory response? Which of the following events occurs first when a wound that breaks the skin has occurred? The site of inflammation may become swollen due to the increased numbers of cells and fluids at the site and painful due to signals from pain receptors.
Antigens, (those are foreign molecules that initiate an immune response) False, (leukocytes of the innate immune system are mast cells, macrophages, and neutrophils) Leukocytes recognize unique molecules on pathogens. (such as the amino acid N-formylmethionine in bacteria. receptor binding=activation of the innate immune response) Macrophages They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream. Platelets release proteins that form clots and decrease bleeding. True
Which cell type carries out humoral immunity?
B cells Humoral immunity involves B cell activation and the production of antibodies by plasma cells.
Ticks that live on deer and field mice are responsible for spreading the bacterium __________, which causes __________.
Borrelia burgdorferi ... Lyme disease The hallmark of infection is a large rash that appears at the location of the tick bite.
Which statement is a correct comparison of an RNA non-retrovirus and an RNA retrovirus?
Both produce protein coats via translation of mRNA. Both regular RNA viruses and retroviruses have genes encoding the protein coats in which they are encased.
In what way(s), if any, is a chemoautotroph different from a chemoheterotroph?
Chemoautotrophs can produce carbon-containing compounds for use in metabolism or for the building of its structures, whereas a chemoheterotroph must consume such compounds.
Which clade of archaea includes most of the extreme thermophiles?
Crenarchaeota
What is the role of dendritic cells in the primary immune response?
Dendritic cells present antigen to, and thus activate, helper T cells. In response, the T cell proliferates.
Which of the following is likely the greatest impact that organisms have ever had on Earth?
Early cyanobacteria released oxygen to Earth's atmosphere during the water-splitting step of photosynthesis.
What is the function of hemagglutinin in the influenza virus?
Hemagglutinin is the protein that helps the influenza virus attach to host cells.
Why can flare-ups of herpesvirus infection recur throughout a person's life?
Herpesvirus can leave its DNA behind as mini-chromosomes in nerve cell nuclei. Stress can trigger another round of virus production, producing characteristic blisters and sores. Herpesvirus remains in a person's cells virtually for their whole lifetime, so flare-ups are always a possibility.
Several scientific laboratories across the globe are involved in research concerning the origin of life on Earth. Which of these questions is currently the most challenging and would have the greatest impact on our understanding if we were able to answer it?
How did RNA sequences come to carry the code for amino acid sequences?
Which of the three types of viruses shown in the figure above would you expect to include glycoproteins as part of their overall structure?
II only
Which of the three types of viruses shown in the figure above would you expect to include glycoproteins as part of their overall structure? (one is hexagon thingy, two is sphere thingy, three is that monster leg thing like from toy story)
II only
You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent .I. Treat the substance with nucleases that destroy all nucleic acids and then determine whether it is still infectious. II. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope. III. Culture the substance by itself on nutritive medium, away from any plant cells. IV. Treat the sample with proteases that digest all proteins and then determine whether it is still infectious.If you already knew that the infectious agent was either bacterial or viral, which treatment listed above would allow you to distinguish between these two possibilities?
III. Culture the substance by itself on nutritive medium, away from any plant cells.
Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O2 reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O2. Consider the colonial aquatic cyanobacterium Anabaena, whose heterocytes are described as having "a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates. Which of the following question arise from a careful reading of this quotation and are most important for understanding how N2 enters heterocysts and how O2 is kept out of heterocysts?
If carbohydrates can enter the heterocysts from neighboring cells via the "intracellular connections," how is it that O2 doesn't also enter via this route?
Chloramphenicol is an antibiotic that targets prokaryotic (70S) ribosomes but not eukaryotic (80S) ribosomes. Which of these questions stems from this observation plus an understanding of eukaryotic origins?
If chloramphenicol inhibits prokaryotic ribosomes, should it not also inhibit mitochondrial ribosomes?
What is an example of the invertebrate defense mechanism?
In insects, an exoskeleton is the first physical barrier against pathogens. The digestive system is protected by lysozyme, a(n) enzyme that breaks down bacterial cell walls and acts as a chemical barrier. The major immune cells are called hemocytes, which carry out phagocytosis and cam secrete antimicrobial peptides.
Which is a characteristic of adaptive immunity?
It has the ability to detect very specific pathogens.
Why is the four stage hypothesis for the abiotic origin of life useful?
It leads to predictions that can be tested.
How do cells involved in the innate immune response detect the presence of pathogens? (how are pathogens recognized as foreign invaders?)
Leukocytes recognize unique molecules on pathogens. Pattern-recognition receptors on leukocytes recognize and bind to unique molecules on the pathogens, such as the amino acid N-formylmethionine in bacteria. This receptor binding leads to activation of the innate immune response.
What happens first when a phage infects a bacterial cell and is going to enter a lysogenic cycle?
Linear DNA circularizes.
When searching for a donor for an organ transplant, doctors try to match the __________ of the donor and recipient as closely as possible.
MHC proteins The major histocompatibility complex is a large set of cell-surface antigens encoded by a family of genes. Foreign MHC markers trigger T cell responses that lead to the rejection of transplanted tissue.
Which of the following cells can engulf a pathogen?
Macrophages. (are leukocytes that can engulf and digest a pathogen)
Why are the curves different? Match the terms in the left column to the appropriate blanks in the sentences on the right. Not all terms will be used.
On the graph A, the number of bacteria increases exponentially and gradually because bacteria spread by binary fission. On the graph B, steps show the periods of viral particles release from dead cells. During replication, the viral particles cannot be detected because this process occurs inside the cell, but at the time of release, their number increases rapidly
Which of the following statements is NOT true? Only some archaea use CO2 to oxidize H2, releasing methane. The cell walls of archaea lack peptidoglycan. Archaea and bacteria have different membrane lipids. Only bacteria have histones associated with DNA.
Only bacteria have histones associated with DNA.
Suppose there is a phagocytic cell in which the pH inside the lysosome is significantly higher than normal. What outcome regarding phagocytosis is most likely to occur?
Pathogens will be able to enter the cell but will not be able to be broken down.
Why do RNA viruses tend to have unusually high rates of mutation?
Replication of their genomes does not involve correcting errors in genome replication.
The structure of a prokaryotic ribosome is not the same as a ribosome in an animal cell. As a result, which of the following is correct?
Some antibiotics can block protein synthesis in bacteria without harming the eukaryotic host.
A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have __________.
T4 protein and T4 DNA
Part complete A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have __________.
T4 protein and T4 DNA
Which example below is a correct statement about Bacteroides thetaiotaomicron, a bacterium that lives in the human intestines?
The bacteria have a mutualistic relationship with the human body. The bacteria obtain food, energy, and shelter in the human intestines. Humans benefit from the many roles these bacteria play, such as involvement in the synthesis of vitamins and the release of antibiotic chemicals that kill other bacteria.
Suppose you get a cut on your finger, and bacteria enter your skin through the cut. What would be the immediate response by your immune system?
The complement system would be activated.
How can up to 9 million mutations can arise each day in the E. coli inhabiting one human?
The mathematics of large population size and rapid reproduction rate combine to produce many mutations without a particularly high mutation rate. Simply by rapid multiplication and a very large population with a normal mutation rate, enormous numbers of mutations can arise in a single day. Even if many of the mutations are lethal, they will hardly make a dent in the population.
In a series of immune system experiments, the thymus glands were removed from baby mice. What would you predict as a likely result?
The mice readily accepted tissue transplants. The thymus is necessary for the proper maturation of T cells. Without helper and cytotoxic T cells, there would no effective immune response.
Which of the following statements correctly describes the lysogenic cycle of lambda (λλ) phage?
The phage genome replicates along with the host genome.
A microbiologist analyzes chemicals obtained from an enveloped RNA virus that infects monkeys. He finds that the viral envelope contains a protein characteristic of monkey cells. Which is the most likely explanation?
The viral envelope forms as the virus leaves the host cell. An enveloped virus is wrapped in host plasma membrane or nuclear membrane (which contains host proteins).
A plant that has been raised in a sterile environment shows symptoms of a viral infection. How would you explain this?
The viral infection was acquired by vertical transmission, ("Vertical transmission" refers to the inheritance of a viral infection from a parent)
The antigen-binding sites of an antibody molecule are formed from the molecule's variable regions. Why do we say these regions are called variable?
Their shape is specific to a particular antibody molecule. The amino acid sequence for these regions varies extensively from one B cell to another
How could this drug prevent infection in someone who is exposed to the flu or could shorten the course of flu in an infected patient (the reasons for which it is prescribed)? Match the terms in the left column to the appropriate blanks in the sentences on the right. Not all terms will be used.
There are 16 different types of hemagglutinin, a protein that helps the virus attach to host cells, and 9 types of neuraminidase, an enzyme that helps release new virus particles from infected cells, which can then invade new cells. Without neuraminidase, infection is is suspected to be limited to one round of replication, rarely enough to cause disease.
How could this drug prevent infection in someone who is exposed to the flu or could shorten the course of flu in an infected patient (the reasons for which it is prescribed)? Match the terms in the left column to the appropriate blanks in the sentences on the right. Not all terms will be used.
There are 16 different types of hemagglutinin, a protein that helps the virus attach to host cells, and 9 types of neuraminidase, an enzyme that helps release new virus particles from infected cells, which can then invade new cells. Without neuraminidase, infectionis is suspected to be limited to one round of replication, rarely enough to cause disease.
Fruit flies normally produce two types of antimicrobial peptides (defensin and drosomycin). Mutant fruit flies were generated that produced no antimicrobial peptides, defensin only, or drosomycin only. Wild-type flies and the mutant flies were then tested for survival after infection with Neurospora crassa fungi or with Micrococcus luteus bacteria. The results are shown in the figures below. These results support the hypothesis that
These results support the hypothesis that
Which is a difference between bacteria and archaea?
They have different chemicals in their cell membranes and cell walls. Bacteria have peptidoglycan in their cell walls; archaea never have peptidoglycan.
How do antiviral drugs help to treat viral infections?
They interfere with viral replication.
The site of inflammation may become swollen due to the increased numbers of cells and fluids at the site and painful due to signals from pain receptors.
True (The site of inflammation may also become red due to increased blood flow at the site; the inflammatory response continues until all invaders are eliminated and the wound is repaired.)
Please use the following information to answer the question(s) below. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from bacteriophages and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.Adherence to the intestinal lining by this bacterium is due to its possession of
a capsule.
Please use the following information to answer the question(s) below. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from bacteriophages and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.Adherence to the intestinal lining by this bacterium is due to its possession of
a capsule.
In insects, which is analogous to mammalian epithelial tissue, in that it serves as a first line of defense against infection?
a chitinous exoskeleton
Which portion of a typical prokaryotic flagellum is embedded in the cell wall and plasma membrane?
a complex "motor"??????
A gram-negative cell wall consists of __________.
a thin layer of peptidoglycan surrounded by an outer membrane containing lipopolysaccharides
Which of the following statements correctly describes the best predictor of how much damage a virus causes?
ability of the infected cell to undergo normal cell division
In 2009, which of the following did scientists discover was possible on early Earth?
abiotic synthesis of RNA monomers
Which of these is NOT part of insect immunity?
activation of natural killer cells
Which of these is NOT part of insect immunity? activation of natural killer cells phagocytosis by hemocytes production of antimicrobial peptides antibacterial digestive enzymes
activation of natural killer cells
An F+ bacterial cell __________.
acts as a donor during conjugation The F+ designation indicates that the bacterial cell has the genes necessary to initiate conjugation and transfer DNA to a receptor cell.
Which subgroup of proteobacteria contains many species that are closely associated with eukaryotic hosts in mutualistic or parasitic relationships?
alpha Members of this subgroup include Rhizobium, which live in nodules within the roots of legumes and convert atmospheric N2 to compounds that are usable by the plants. This group also gave rise to mitochondria.
A human pandemic is __________.
an epidemic that extends around the world
Local swelling, increased blood flow, and fever are all parts of __________.
an inflammatory response, This line of defense includes phagocytic white blood cells, antimicrobial proteins, and the inflammatory response.
The following question(s) are based on the observation that several dozen different proteins comprise the prokaryotic flagellum and its attachment to the prokaryotic cell, producing a highly complex structure.If the complex protein assemblage of the prokaryotic flagellum arose by the same general processes as those of the complex eyes of molluscs (such as squids and octopi), then
ancestral versions of this protein assemblage were either less functional or had different functions from modern prokaryotic flagella.
The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can then reactivate, replicate again, and be infectious to others.In order to be able to remain latent in an infected live cell, HSV must be able to shut down what process?
apoptosis of a virally infected cell
Bacteria that __________ tend to have abundant internal membranes.
are photosynthetic Cyanobacteria have thylakoid membranes, much like those in chloroplasts, that function in photosynthesis.
Juan is a 5-year-old boy and recently recovered from the chickenpox. He returned to kindergarten and found out that his friend Tram had chickenpox too. Normally chickenpox is very infectious, but Juan did not acquire it again. Why was Juan protected from a second exposure to chickenpox?
because his immune system now has immunological memory
According to the graph, B cells will first produce effector cells
between 7 and 14 days.
Septic shock, a systemic response including high fever and low blood pressure, is a response to
certain bacterial infections.
The nucleic acid of a virus particle is enclosed in a protein coat. What is this protein coat called?
capsid
Complete the replicative cycle of a virus with a single-stranded genome that can function as mRNAmRNA. Drag the appropriate labels to their respective targets. Not all labels will be used.
capsid proteins, glycoproteins, viral genome, complementary strand, new viral genome
The nucleic acid of a virus particle is enclosed in a protein coat. What is this protein coat called?
capsid, (the protein shell that encases a viral genome)
Although not present in all bacteria, this cell covering often enables cells that possess it to resist the defenses of host organisms, especially their phagocytic cells.
capsule
Choose the list below that contains the substances required by typical nitrogen-fixing cyanobacteria.
carbon dioxide, nitrogen, water, light, and some minerals These bacteria are considered some of the most self-sufficient of all organisms.
Some people who have had a herpesvirus-mediated cold sore or genital sore may have flare-ups for the rest of their life. Why does this occur?
copies of the herpesvirus genome remaining as mini-chromosomes in some host cell nuclei
Restriction enzymes help defend bacteria against viral infections by __________.
cutting viral DNA once it has entered the cell Restriction enzymes cut viral DNA, but bacterial DNA is modified in such a way as to protect it against the enzymes.
Plantlike photosynthesis that releases O2O2 occurs in __________.
cyanobacteria
An otherwise healthy student in your class is infected with EBV, the virus that causes infectious mononucleosis. The same student had been infected when she was a child, at which time she merely experienced a mild sore throat and swollen lymph nodes in her neck. This time, although infected, she does not get sick. Her immune system's recognition of the second infection involves the
cytotoxic T cells.
Which subgroup of proteobacteria contains many species that are predators of other bacteria?
delta This group includes species that congregate into relatively large slimy colonies and species that are predators of other bacteria.
Our immune system does not usually attack our own healthy tissues because such lymphocytes are __________.
destroyed or rendered nonfunctional Some B and T cells that have receptors for the body's own molecules are destroyed by apoptosis; others are rendered nonfunctional.
The number of major histocompatibility complex (MHC) protein combinations possible in a given population is enormous. However, an individual in that diverse population has a far more limited array of MHC molecules because
each of the MHC genes has a large number of alleles, but each individual only inherits two for each gene.
Bacterial flagella have a very complex structure composed of 42 distinct proteins. What is the most likely explanation for the evolution of these complex structures?
exaptation Proteins that were already part of the bacterial body were modified through natural selection to take on new functions as the bacterial flagella.
Which of the following describes an organism that obtains both carbon and energy by ingesting prey?
heterotroph and chemotroph
An inflammation-causing signal released by mast cells at the site of an infection is (are)
histamine
In the absence of meiosis and sexual reproduction, what general process allows genetic recombination among prokaryotes?
horizontal gene transfer Horizontal gene transfer by way of transformation, transduction, and conjugation allows bacteria to share genetic material and recombine it.
Portions of the genomes of certain prokaryotic species are very similar to portions of the genomes of distantly related prokaryotes. The process that most likely accounts for this genetic similarity is __________.
horizontal gene transfer Prokaryotes are adept at obtaining DNA from other sources, including other species of prokaryotes, through the processes of conjugation, transformation, and transduction.
Scientists hypothesize that the O157:H7 strain of E. coli is so different from the K-12 strain because of __________.
horizontal gene transfer over many years, most likely through the action of bacteriophages
In the figure above, at the arrow marked II, what enzyme is being utilized?
host cell DNA polymerase
A vaccine may contain __________.
inactivated disease-causing microbes Inactivation may result from killing the organisms or by treatments that weaken or remove the disease-causing aspects while leaving antigens intact.
The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can then reactivate, replicate again, and be infectious to others.If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection?
interference with new viral replication in preexisting cases
Suppose that a mosquito has been internally infected by a potentially pathogenic fungus. What will help protect it from the infection?
its antimicrobial peptides
B lymphocytes __________.
multiply and make antibodies that circulate in blood and lymph B lymphocytes that secrete antibodies are called plasma cells.
The early atmosphere may not have been as reducing as originally postulated by Haldane, Oparin, Miller, and Urey. In light of current thinking about the composition of the early atmosphere, what is regarded as a likely place for the abiotic synthesis of organic molecules to have occurred?
near volcanoes Recent analyses of the amino acids produced by Miller have shown that they formed under volcanic conditions.
The Desulfovibrio bacterium breaks down organic matter (which it must have) and uses sulfate (not oxygen) as an electron acceptor. Oxygen is a deadly poison to Desulfovibrio. We would call Desulfovibrio a(n) __________.
obligately anaerobic chemoheterotroph Obligate anaerobes are poisoned by oxygen. Chemoheterotrophs must consume organic molecules for both energy and carbon.
On early Earth, more than 4 billion years ago, environmental conditions were very different from those today because
only early Earth was intensely bombarded by large rocks and ice from space.
When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?
only the nucleic acid After attaching to receptors on the surface of the bacterial cell, the virus injects its DNA into the cell.
What is the term for a virus that attacks a bacterium?
phage
Which viruses have single-stranded RNA that acts as a template for DNA synthesis?
retroviruses
Birds act as a natural __________ for the influenza __________ virus.
reservoir ... A
HIV uses which of the following processes to synthesize a DNA strand using its RNA genome as a template?
reverse transcription
Several scientific laboratories across the globe are performing research concerning the origin of life on Earth. Suppose one of these laboratories conducts abiotic experiment(s) to test the potential for hydrogen bonding between various nucleic acids and amino acids. Which of the following results of such experiments are most consistent with our current understanding of Earth's first genetic systems?
rna amino acid is highest
As a result of the lytic cycle, _____.
the host cell's DNA is destroyed, (when the host cell's DNA is destroyed, ultimately, the host cell itself is destroyed in the lytic cycle.
Which photograph in the figure shows the cellular structure observed in species such as Staphylococcus epidermis, Staphylococcus aureus, and Streptococcus pneumoniae?
spherical
The following question(s) are based on the observation that several dozen different proteins comprise the prokaryotic flagellum and its attachment to the prokaryotic cell, producing a highly complex structure.Certain proteins of the complex motor that drives bacterial flagella are modified versions of proteins that had previously belonged to plasma membrane pumps. This evidence supports the claim that
structures originally adapted for one purpose can take on new functions through descent with modification.
Infection by a bacterium that has elements on its surface that enhance its resistance to lysozyme will likely result in
successful reproduction of the bacterium and continued progression of the disease.
Cave art by early humans recognized the existence of the major signs of inflammation. The most inclusive set of symptoms of inflammation that might appear in such early human art is
swelling, heat, redness, and pain.
Which of the following is the correct sequence of events in the origin of life?
synthesis of organic molecules, synthesis of organic macromolecules, formation of protocells, formation of DNA-based genetic systems
Abiotically-produced vesicles display which rudimentary quality necessary for life?
the ability to perform simple reproduction and metabolism Abiotically produced vesicles are capable of dividing and performing simple metabolic reactions.
Immunological memory accounts for
the ancient observation that someone who had recovered from the plague could safely care for those newly diseased.
Phagocytosis is best defined as __________.
the cellular ingestion and digestion of foreign substances
Fruit flies normally produce two types of antimicrobial peptides (defensin and drosomycin). Mutant fruit flies were generated that produced no antimicrobial peptides, defensin only, or drosomycin only. Wild-type flies and the mutant flies were then tested for survival after infection with Neurospora crassa fungi or with Micrococcus luteus bacteria. The results are shown in the figures below. These results support the hypothesis that
the drosomycin gene protects flies from fungal infection.
In the lytic life cycle of phages __________.
the host cell typically dies, releasing many copies of the virus After attaching to receptors on the surface of the bacterial cell, the phage injects its nucleic acid into the cell. The phage then hijacks the cellular machinery to manufacture many copies of itself.
Several scientific laboratories across the globe are performing research concerning the origin of life on Earth. Suppose one of these laboratories conducts abiotic experiment(s) to test the potential for hydrogen bonding between various nucleic acids and amino acids. Which of the following results of such experiments are most consistent with our current understanding of Earth's first genetic systems?
the one that has RNA amino acid as the tallest bar
Viruses can vary according to the following characteristics, except for __________.
the presence or absence of metabolic machinery Viruses are not classified by the presence or absence of metabolic machinery, because viruses lack the structures and metabolic machinery found in a cell.
The idea behind vaccination is to induce __________ without requiring the vaccinated individual to get sick.
the primary immune response Ideally, the vaccine will consist of the antigen with the disease-causing aspects of the microorganism removed.
HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because __________.
the virus binds to specific receptors that are only present on certain immune cells The virus binds to receptors, such as CD4, that are only present on certain cells such as helper T cells.
You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. Treat the substance with nucleases that destroy all nucleic acids and then determine whether it is still infectious. II. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope. III. Culture the substance by itself on nutritive medium, away from any plant cells. IV. Treat the sample with proteases that digest all proteins and then determine whether it is still infectious. If you already knew that the infectious agent was either bacterial or viral, which treatment listed above would allow you to distinguish between these two possibilities?
uh idk maybe release nuclease maybe not sorry dude
The atmosphere of early Earth probably contained no O2 until the emergence of organisms that __________.
used water as an electron source for photosynthesis. (oxygen began to accumulate in the atmosphere due to the action of photosynthetic cyanobacteria)
What is the most effective way to stop viral infections?
vaccines, (vaccines stimulate the immune system to recognize and effectively fight off invading viruses. They have proven to be the most effective weapon against viruses)
In the lysogenic cycle _____. Cycle A is the _____ cycle and cycle B is the _____ cycle.
viral DNA is replicated along with host DNA, (viral DNA, incorporated into host DNA as a prophage, is replicated along with host DNA) lytic ... lysogenic (The lytic cycle concludes with rupture of the host cell. The lysogenic cycle involves replication of viral DNA along with replication of the host.)
A prophage is a(n) __________.
viral genome that has been incorporated into a bacterial cell's chromosome
The pointer is indicating the _____. (it is in the middle of the top half and is just pointing to the surface level/outer layer)
viral protein coat, (The viral protein coat surrounds its genome.)