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Biology Exam 3
Terms in this set (214)
Natural selection for a certain phenotype will affect the
allele frequency of a population
When bird populations migrate and mix with populations that do not migrate this can cause
Genotypes are said to be in ________ equilibrium if there is random mating and no other forces tend to alter the proportions of alleles from one generation to the next.
The key point in Darwin's proposal is that the ________ imposes the conditions that determine the direction of selection.
Natural selection, as a mechanism of evolution that acts on variants within populations and ultimately leads to the evolution of different species, was proposed by
In the Hardy-Weinberg equation, p and q are
A restriction in genetic variability caused by a drastic reduction in population size is called a
Reproductive success of an individual is known as
Darwin proposed that natural selection occurs in an environment by
favoring heritable features that make the organism better suited to survive and reproduce
In the Hardy-Weinberg equations, the frequencies of 2 alleles in a population (where there are only 2 alleles to consider) can be designated as
p and q
"The inheritance of acquired characteristics" proposal was put forward by
The frequency of a particular allele within a population can be changed over time by
The genetic preservation of the features that increase the likelihood of survival and reproduction of some individuals within a population is called the process of
There are more than 30 blood group genes in humans, in addition to the ABO locus. If an additional set of previously unknown blood group genes were used to determine blood groups, this would effectively increase ________ in human populations.
Two parents who do not have sickle cell anemia but are less susceptible to malaria have a child who has the disease. The parents are both
heterozygous for the sickle cell allele
For a gene with two alternative alleles, A (with a frequency of p) and B (with a frequency of q), the term in the algebraic form of the Hardy-Weinberg equilibrium that represents the heterozygote genotype frequency is
The observation that most pureblood Native Americans have type O blood is best explained by
a founder effect
Female cardinals select male mates in part based on their bright red color. What effect would this have on a cardinal population that was in Hardy-Weinberg equilibrium?
The frequency of red alleles would be greater than those predicted by Hardy-Weinberg equilibrium
You spray your kitchen with an insecticide to kill the cockroaches. A few survive and reproduce, producing a large healthy population in a few generations that all have similar genetic backgrounds. This is an example of
Some flowering plants cannot self-pollinate, which increases their tendency to mate with phenotypically different mates, a process called disassortative mating. What effect would this have on a population in Hardy-Weinberg equilibrium?
An increase in heterozygotes would be observed
Being born with extra fingers on a hand is called polydactyly. This is more common in some populations in North America than others due to
a founder effect because their ancestors from Europe carried the alleles
In a forest, trees that get more sunlight grow taller than other nearby trees. This is a form of
Certain small towns in the western United States have remained isolated since their settlement many years ago. Some alleles are more common in these communities as compared to the rest of the US population. This difference is a result of
the founder effect
Cheetahs that experience a genetic bottleneck would be characterized by evidence that shows
there is very little genetic variability
Animals that select mates that are phenotypically similar will have ________ when compared with Hardy-Weinberg predictions.
If a population was in Hardy-Weinberg equilibrium then ________ would occur in that population.
no evolutionary changes
An island is on the migration route of sea birds. What best describes the way this will change Hardy-Weinberg equilibrium in non-migrating populations, if the migrating birds have very different allelic frequencies?
The 0.5 equilibrium will be greatly altered due to influencing frequencies from migrating birds.
In some instances environmental change causes a situation where one phenotype is favored for a period of time, and then a different phenotype is favored. This oscillating selection causes
the maintenance of genetic variation in the population
People homozygous for the sickle-cell anemia allele develop a life threatening disease, while those homozygous for the normal allele are at the highest risk of dying from malaria. Carriers have some resistance to malaria, but do not develop sickle cell anemia. This is an example of
During a drought on the Galapagos islands, finches with larger beaks were able to crack the large tough seeds produced by plants that survived the dry conditions. This is an example of
The factor that would be expected to produce the largest evolutionary change in a given period of time in a bird population is
The disease sickle-cell anemia is common in malaria-infested areas because individuals that are heterozygous for the gene (AS) have enhanced resistance to malaria over normal individuals (AA). Individuals with severe sickle-cell anemia (SS) usually die before reproduction. If this population moves to an area without malaria, what will happen to the allele frequency of the A allele over time?
It will go up because there is no malaria
The California populations of the Northern elephant seal are descendants from a very small population of seals that was over-hunted in the 1890s. Heterozygosity in this population would be expected to be ________ due to ________.
slight; a bottleneck effect
The several hundred species of picture-winged fruit flies of the Hawaiian Islands are genetically very similar, yet they all differ markedly from their ancestral population in Asia. This is mainly accounted for by
An insect population that becomes resistant to a commonly used insecticide is an example of
The organism with the highest fitness is an animal that lives
10 years and produces 10 offspring per year
A population of lizards lives in a rocky area next to a desert. Some lizards are light colored and blend into the sand, whereas others are dark and blend into the rocks. Over time, this lizard population is likely to
evolve into two separate species as a result of disruptive selection
Both extremes of an array of phenotypes are favored in
In early ancestors of the modern giraffe, longer necks allowed animals to reach higher tree branches as food. This would lead to ________ in the ancestral giraffe population.
The midrange of an array of phenotypes is favored in
Average human males are most likely to be attracted to women with a specific waist to hip ratio. Women with this waist to hip ratio are also the most fertile. By being attracted to women with a waist to hip ratio, a male is increasing his chances of having children and thus improves his
A selection experiment you are doing requires certain conditions in order for evolutionary change to occur. What conditions would cause this change?
Variation between individuals in a population
Genetic variations being heritable
Survival rate of offspring varying due to parental genetic differences
In the lab you show that guppies under different predatory conditions change in rapid evolution. In the field you wish to design an experiment that would generate data to support your observation. What experiment would best help you achieve your goal?
Transfer wild guppies from a predator free pond into one with predators but no guppies, over time observe the guppies for physiological changes
In both field and lab studies of guppies, you observe a rapid evolutionary change in the physiological traits that help the animals avoid predation. This observation illustrates which main point?
Natural selection is an ongoing process
Evolutionary change is facilitated by natural selection
Hardy-Weinberg states out that original genotype proportions within a population remain constant across generations if certain assumptions were met. These assumptions include
the occurance of random mating
the lack of selection
a large population size
an absence of gene flow
Mutations affect Hardy-Weinberg equilibrium by
altering frequencies of particular alleles within a population
Which statement applies to artificial but not natural selection?
Phenotypic variation of a species has variable appeal to humans interested in that species
Artificial selection involves a selective breeding to enhance desirable traits
A new plant species is introduced to Daphne Major and produces small, thin seeds. This plant species is highly adapted to drought and after 5 years has replaced over 80% of the native plants that produce large seeds. How will this change affect the evolution of beak size in the medium ground finch population?
Small beaks will be favored under all rainfall conditions
A new plant species is introduced to Daphne Major and produces small, thin seeds. This plant species is highly adapted to drought and after 5 years has replaced over 80% of the native plants that produce large seeds. How will this change affect the evolution of beak size in the medium ground finch population?
Considerable variation existed in the beak size and shape of this finch
Beak shape (depth) varied with the dryness of the year
Offspring were similar to parents in beak size and shap
In studying the medium ground finch on Daphne Major, the Grants noted that each generation of finches had beaks
best suited for their parents' environment
Industrial melanism is a term
describing the evolutionary process in which initially light-colored organisms become dark as a result of natural selection
The evidence for industrial melanism being caused by an increase in the dark allele was provided from field tests carried out by
The shape of the beaks of Darwin's finches and industrial melanism are often cited as examples of the process of _______________ leading to evolutionary change.
Natural selection occurred in both of these examples; the pressures leading to the selection of deeper beaks following drought or darker pigmentation following pollution were environmental changes. Natural selection is the change in allele frequencies from one generation to the next in response to changes in environmental pressures.
Natural selection has favored the dark form of the peppered moth in areas subject to severe air pollution, perhaps because on darkened trees, moth-eating birds see them less easily. As pollution abated, the light forms increased in the population because
light moths were able to produce more offspring than dark moths
Industrial melanism involving the peppered moths (Biston sp.) is cited as an example of natural selection that has been observed in the last one hundred years. Recall that the peppered moth exhibits two distinct morphological types with dark and light colored wings. Which of the following statements about changes in these two types of moths as a result of industrial melanism is true?
The dark forms are selected against in nonpolluted forests
In a hypothetical study, equal numbers of marked dark and light moths are released in polluted and unpolluted woodlands and recaptured 10 days later. According to the industrial melanism hypothesis, which of the following results is unexpected?
Fewer unmarked dark moths should be captured in polluted woodlands than unmarked light moths
You would not expect there to be more light moths (either marked or unmarked) than dark moths in a polluted forest, since dark moths are more well-camouflaged and thus should be more numerous after 10 days of predation by birds.
Indicate which factors support the industrial melanism hypothesis. Check all that apply.
Dark moths have greater camouflage on trees in polluted woodlands
Pollutants darken bark surfaces
Which "alternate" hypothesis might also explain industrial melanism?
Dark moths are more resistant to the toxic effects of pollution than light moths
Domestication of dogs has led to
a variety of phenotypes
Comparing the evolution of domesticated dogs to the evolution of wolves over the same time period illustrates what relationship between artificial and natural selection?
Artificial selection is more likely to produce maladaptive structures than natural selection
Considerably more phenotypic variation exists in domesticated varieties of species like dogs and cabbages than exists in non-domesticated species like lions and maple trees. Which one of the following statements best explains why this is true?
Many domesticated varieties would not survive in the natural world
Some of the most dramatic evidence for evolution has come from human agriculture. One of the most highly artificially selected crop plants is
A technique used in dating a rock can be used to accurately predict the age of the fossils occurring in the rocks. This technique involves
radioactive isotope decay
Today, the fossil record
can be dated reasonably well using a variety of radioactive isotopes with known half-lives
Progressive changes in the fossil record are evidence for evolution because
they show descent with modification
The most likely explanation for why toothed whales have a blowhole is
they evolved from an animal with nostrils
Radioactive isotopes are used in dating materials from the distant past. Which of the following statements about radioactive dating techniques is true?
It uses a technique in which the degree of radioactive decay is measured, the older the rock the more radioactive decay.
A rock contains 18 mg of the radioactive isotope carbon-14. The half-life of carbon-14 is 5,600 years. How many half-lives and years will it take before the carbon-14 decays to less than 4 mg? A. 1 half-lives; 5,600 years
3 half-lives; 16,800 years
The half-life of carbon-14 is 5,600 years. A fossil that has one-eighth the normal proportion of carbon-14 to carbon-12 is probably
16,800 years old.
Which one of the following features of Archaeopteryx clearly demonstrates that it was on the evolutionary line leading from dinosaurs to birds?
Choose the true statement(s) about the evolutionary divergence of horses in North America. Check all that apply.
Most changes are seen as adaptations for life in grassland habitats.
The general trends during horse evolution are increase in body size, lengthening of limbs, reduction of digits on both sets of limbs, and tooth development for a grazing life style.
Living lineages of horses show much less diversity than existed in the past.
In 2006, scientists discovered a fossil that had scales and gills, a flat head with eyes on top like a crocodile, and fin and neck bones that would allow it to prop itself out of the water. The best explanation for this fossil is that it is
a transitional fossil between fish and amphibians
Which of the following features of ancient horses are adaptations for living on open grasslands? Check all that apply.
complex patterns of ridges on molar and premolars that increased chewing ability
lengthening of limbs that increased running speed over long distances
The most precise method of obtaining estimates of the absolute ages of geological deposits is
measure the ratios of various radioactive isotopes in the deposits
The size and shape of a finch's beak correlates with it's ______.
choice of food
Structures that have no apparent function but had a function in ancestral species are
Homologous structures are
structures of animals that have different appearances and functions but seem to have evolved from the same body part in a common ancestor
The side toes of a horse, the pelvis of the whale, and the human appendix are all examples of structures that resemble structures of presumed ancestors, which are known as
You would predict to see the fewest amino acid sequence substitutions in a protein between a human and a ____.
During development in the mother's uterus, human embryos have pharyngeal pouches (sometimes called gill slits) that later develop into various glands. Fish also have pharyngeal pouches as embryos, but these develop into gills. The best explanation for why human and fish embryos develop pharyngeal pouches is
humans and fish share a common ancestor that had gills
Many developmental features reflect the common ancestry of vertebrates. Many vertebrate embryos are nearly indistinguishable in the early stages to all but developmental biologists; the different species begin to differentiate as development progresses.
The evolution of similar forms in different lineages when exposed to the same selective pressures is
A new winged species is discovered in the Amazon rainforest. Select the evidence that supports that this species' wings are homologous to vertebrate animals and analogous to insect wings. Check all that apply.
The wings have an underlying bone structure
Blood vessels are networked through the wings
Which observations illustrate shared ancestry by anatomical comparison studies? Check all that apply
A structure becomes vestigial
Structures are found to be homologous
The same structure has evolved to carry out different functions
The observation that different geographical areas sometimes exhibit plant and animal communities of similar appearance, even though the individual plants and animals are not closely related, is called
The pair of traits that best illustrates convergent evolution is
a cartilage skeleton in a shark and a bone skeleton in a dolphin
Convergent evolution occurs when two species living in
different areas evolve similarities through natural selection acting on those characteristics
Choose the true statements about species that show convergent evolution. Check all that apply.
they do not share a recent common ancestor
they are subject to similar selection pressures
they have similar phenotypes
The extinct marsupial wolf in Australia closely resembled canines in the rest of the world. This is an example of
The streamlined bodies seen in sharks, tuna, and dolphins best relate to
the physical properties of water
The pattern of wet years and dry years shown will probably move the population toward
maintaining abundant variation in beak depth
Which statement best describes the correlation between beak depths of Geospiza fortis on the Galápagos island Daphne major and the dryness of the environment?
Birds with large beaks are favored during dry years
In the laboratory, fruit flies (Drosophila) were artificially selected for the number of bristles on their bodies. One population (R) was selected for low numbers of bristles, a second population (S) for high numbers of bristles.
genetic variation had to be present in the population
After 35 generations (about 1 year's time), the two populations R and S were studied. Researchers found
a huge increase in S, a huge decrease in R, with no overlap whatsoever.
Marsupials are a very ancestral form of mammal, evolving before placental mammals over 70 million years ago. Today Australian marsupials can be compared to placental mammals on other continents.
When you compare Australian marsupials to placental mammals today
the marsupials are very similar to placental mammals in the ways they have adapted to similar ecological niches.
Australian marsupial kangaroos and placental deer graze on grass with similar teeth. These species have
undergone convergent evolution
Choose the evidence supporting that snakes evolved from legged lizards. Check all that apply.
Snakes have pelvic bones.
The oldest snake-like fossils have leg bones.
Snake embryos temporarily develop limb buds which are reabsorbed before birth.
Plants in the desert-adapted families Cactacea (cactus) and Euphorbia (euphorbs) share many of the same physical characteristics, such as succulent stems that store water and CAM photosynthesis, but they do not share a recent common ancestor. This evidence suggests that these families are an example of
The figure below shows the relationship between beak depth in the medium ground finch on Daphne Major and relative fitness. Assuming that beak depth is heritable, what do you predict about beak depth in the next generation?
Mean beak depth will stay about the same
Select the pairs of organism characteristics that are homologous structures. Check all that apply.
cactus spines; tree leaves
human hand bones; whale fin bones
A scientist studying evolution of peppered moths (Biston betularia) in Michigan observed that the percentage of melanic moths increased by around 2% from 1960-1961. Has evolution occurred in this population?
Yes, because the frequency of the melanic moths in the population changed over time
Scientists estimate that as much as one-fourth of all species will become extinct in the near future, a rate of extinction not seen on Earth since the Cretaceous mass extinction. How are humans contributing to this mass extinction? (Check all that apply)
Contributing to climate change
he most famous and well-studied mass extinction occurred at the end of the Cretaceous period (65 million years ago), at which time the dinosaurs and a variety of other terrestrial and aquatic organisms went extinct. Recent findings have supported the hypothesis that this extinction event was triggered when a large asteroid slammed into Earth. Which of the following could cause a global mass extinction following an asteroid strike? (Check all that apply)
The impact triggered global forest fires that obscured the sun.
The asteroid created a massive dust cloud that obscured the sun.
Diversification of mammals after the extinction of the dinosaurs is considered an adaptive radiation because a few mammal species rapidly evolved into most of the current mammalian lineages in a relatively short amount of time. This diversification was partially driven by the evolution of endothermic homeostasis in mammals, which is in example of
a key innovation
Select the reasons why adaptive radiations are often observed on remote volcanic islands. Check all that apply.
When a new volcanic island forms, there are many empty niches.
Only a few individuals reach remote islands.
Indicate the scenario(s) that could directly result in sympatric speciation. Check all that apply.
Two sunflower species cross to form a healthy hybrid individual with equal copies of chromosomes from each parental species
A subset of parasitic flies within a larger population colonizes a new host plant
Scientists investigating speciation in fruit flies divided a single population of flies into separate populations that each lived in their own cage on one of two food sources: maltose-based food or starch-based food. After several generations, the flies' mate preference was tested, and it was found that flies strongly preferred to mate with other flies that were raised on the same food source. This results suggests that
selection on food source indirectly led to the evolution of reproductive isolating mechanisms
Two species regularly come into contact and form hybrids that have higher fitness than either of the parental species. What are the possible consequences of regular hybridization between these species? Check all that apply.
evolution of a third species
extinction of the parental species
increased gene flow between the parental species
Reinforcement is most likely to drive the evolution of
prezygotic isolating mechanisms, because selection favors alleles that prevent hybridization
An example of temporal isolation would be
one plant species blooms in June-July and a second plant species blooms in August-September
Choose the best cause and effect sequence for the process of speciation by natural selection.
Mutation --> Variation --> Selection --> Reproductive Isolation --> Speciation
Which statements about the adaptive radiation of New Zealand alpine buttercups are true? Check all that apply.
Divergence occurred mainly during periods of glacial advance.
The availability of a variety of habitats favored diversification.
Reproductive isolation was reinforced mainly during periods of glacial recession.
Which statements about the Lake Victoria cichlid fishes are true? Check all that apply.
The adaptive radiation of the estimated 300 species of cichlid fish was very rapid and took place during the last 200,000 years.
The adaptive radiation of the Lake Victoria cichlids may have resulted from a key evolutionary innovation.
Many of the Lake Victoria cichlids have very specialized adaptations that allow them to occupy diverse habitats within the lake.
Choose the true statements about the diversity of Darwin's finches on the Galápagos Islands. Check all that apply.
Competition among finches for food sources led to character displacement of beak shapes.
All of the finch species share a common ancestor that colonized the islands
Choose the factors contributing to adaptive radiation of Drosophila in the Hawaiian Islands. Check all that apply.
New islands are constantly being formed.
The islands are highly volcanic.
If a new species is produced by the interbreeding of two members of distinct species, this would be __________ speciation achieved via _________.
If two species are able to mate and produce an offspring which can mate with itself, but is unable to mate with either parent's species, it is an example of
sympatric speciation via polyploidy.
Imagine two species of birds with similar beak sizes and diets. Where the two species are allopatric, we would expect that their beak sizes
should differ less than when sympatric.
Why do the Galápagos Islands and the Hawaiian Islands have so many endemic species of flies and birds? Check all that apply.
There are numerous islands in each archipelago.
There is adequate distance between islands to allow divergence.
The founder effect was common when islands were colonized.
Due to character displacement, two closely related species may differ most morphologically when they
Many male songbirds have very distinctive songs that are used to attract females. These songs are an example of a(n) ________ isolating mechanism.
Several species of sea urchins may inhabit the same tide pool and their reproductive periods overlap. Although they practice external fertilization, they seldom interbreed because eggs produce chemicals that are only attractive to sperm of their own species. This is an example of a _________ barrier involving _______________.
prezygotic; gametic isolation
Which statement is true about speciation on island archipelagos?
Most speciation occurs allopatrically.
Indicate which examples would be considered different species under the Biological Species Concept. Check all that apply.
Two bear species that are able to breed in zoos but have separate ranges in nature.
Two skunk species that look morphologically similar but are unable to interbreed.
Two plant species with no gene flow between them
The biological species concept of Ernst Mayr cannot be applied to
Two populations that inhabit the same area but remain genetically distinct can best be called
Lake Victoria is famous for its variety of cichlid fishes. In fact, they offer the most diverse assembly of vertebrates presently known to science. One trait that scientists have focused on as one possible reason for their adaptability is
a second set of jaws in their throats.
The most common mechanism for sympatric speciation in plants is
Adaptive radiation is best described as the
existence of groups of closely related species recently evolved from a common ancestor.
Two bird species have different mating calls, occupy different habitats in nature, and when they hybridize, the hybrids are infertile. Which isolating mechanisms maintain these species?
ecological isolation, behavioral isolation, and hybrid sterility
A virgin pine forest covers a valley, and one of the inhabitants is a red squirrel species. A large volcanic eruption occurs and separates the valley with a huge lava flow that the squirrels cannot cross, thus producing two isolated populations of squirrels. What change needs to occur for the two populations of squirrels to become separate species?
The two squirrel populations become reproductively isolated.
Two hundred years ago, the fly species Rhagoletis pomonella only laid its eggs on fruit of the hawthorn tree. Today, different "host races" of R. pomonella lay their eggs on hawthorns OR apples. Apples occur within the range of hawthorns, so divergence between apple flies and hawthorn flies could be the first step in sympatric speciation. Choose the evidence that supports that R. pomonella is undergoing sympatric speciation. Check all that apply.
Apple flies typically mate with apple flies, and hawthorn flies typically mate with hawthorn flies.
Apple flies and hawthorn flies emerge from their hosts at different times of the year.
Select the concepts emphasized by Ernst Mayr's biological species concept. Check all that apply.
Reproductive isolation from other species
Production of fertile offspring within the species
Check all that apply: Members of the same biological species can
have several isolated gene pools.
differ from other species in one or more characteristics.
interbreed freely with each other.
Species formation among alpine buttercups in New Zealand was promoted by
periodic isolation by glaciation.
Very rapid speciation occurred when cichlid fishes were isolated in Lake Victoria. Widespread extinction was dramatically seen when
predatory fish were added.
Scientists studying a group of related bird species on an island archipelago discover that these species are always more closely related to each other within an island than they are between any two islands. The most likely explanation for this result is that
one bird species colonized each island and then evolved into distinct species on that island through character displacement.
Select the postzygotic isolating mechanisms. (Check all that apply).
Hybrids are sterile.
Hybrids develop abnormally.
Hybrids fail to become established in nature.
The hundreds of species of Drosophila in Hawaii exhibit different mating rituals. This isolating mechanism is
prezygotic and behavioral.
In the southeastern U.S., two species of wild lettuce (Lactuca) do not usually form hybrids, because they bloom at different seasons. The means of isolation appears to be
prezygotic and temporal.
Prezygotic mechanisms lead to reproductive isolation by preventing the formation of
Males of several marsupial species have forked penises that are incompatible with female placental mammals. This is an example of what type of isolating mechanism?
Many species might coexist in a particular environment by occupying ecological
Once species have formed, they keep their identity
Scientists found that different beak shapes lead to different mating songs in Darwin's finches. This result best supports which hypothesis?
Adaptation to different food sources indirectly led to behavioral isolation in Darwin's finches.
If species are competing for the same resource natural selection will drive the evolution of ____.
If populations within the same area split into species, the process is known as
According to the Biological Species Concept, two groups of organisms that are unable to form fertile, viable hybrids are considered to be different
Hybridization regularly occurs between three species of Darwin's finches on Daphne Major, but the finches are still considered different species because
they occupy different niches.
Evolution acts at the level of the
Which isolating mechanism is postzygotic?
A type of isolating mechanism that leads to reproductive isolation after a hybrid zygote has formed is called a _____________ isolating mechanism.
When two species cannot form hybrid zygotes, the mechanism that keeps the species separate is known as a _____________ isolating mechanism.
The type of speciation that results in the formation of separate species as a result of geographic isolation is called ____________ speciation.
The process by which related species evolve to more different in order to reduce competition is called ___________ _________.
The phenomenon where one species diverges into many by occupying a series of different habitats within a region is called __________ _________.
Reproductive isolation is ______ by natural selection to lead to speciation
incomplete isolating mechanisms are reinforced by natural selection until they are completely effective.
The _______ definition of species says that a species is a group of organisms that are reproductively isolated from other such groups.
A layer of lipoprotein and glycoprotein that covers the outer surface of some viruses is the
Plasma from a sick mouse is filtered across a membrane that has a 200 nm pore size. If the filtrate is still infectious if injected into a healthy mouse, then the pathogen is most likely a(n):
Tetracycline is effective against viruses because it disrupts the action of the viral ribosomes.
If the gp120 glycoprotein were damaged as a result of a mutation, HIV would have difficulty:
binding to a host cell
Which class of drugs would be effective against HIV but not against most other pathogenic viruses?
Non-nucleoside reverse transcriptase inhibitors that block reverse transcription.
Retroviruses are unique because they are a combination of RNA and DNA.
Can a virus be killed?
No, viruses are non-living and cannot die.
An experimental chemical has been shown to selectively cleave phosphodiester bonds. How would the affect a virus?
Fragment the genome
Viruses are self-replicating but the replication is much faster in a host cell.
Why do viruses only infect specific types of cells?
The host cells have the correct surface receptor that the virus can fit into.
A mutation in the gene encoding the integrase enzyme renders the protein non-functional. How would the affect the HIV infection cycle?
Formation of the provirus would be stopped.
The human immunodeficiency virus (HIV) is so named because it cripples the immune system by attacking and destroying helper T cells (TH cells). What cell surface protein does the HIV virus most likely use to bind to and infect the TH cells?
In the old days, milkmaids were exposed to cowpox from milking the cows, and this fortuitously gave them some protection from smallpox. What was happening in the milkmaids?
They were effectively receiving a vaccination from a related virus.
Why must T cell activation take place outside the thymus?
Many T cells are self-reactive and must be eliminated in the thymus before any possibility of activation.
What is a consequence of the fact that the chickenpox virus has a much lower mutation rate than the influenza virus?
A chickenpox infection generally gives immunity against a repeat infection, but people can catch the flu every year.
Every year a new version of the flu vaccine is made using a mixture of strains. The strains are chosen based on surveillance and analysis by experts from the FDA, WHO, and CDC. For other diseases however, such as varicella (chickenpox), the same vaccine is used continually and repeated vaccinations are not necessary. What do you conclude is the important difference between the influenza virus and the varicella zoster virus with regards to vaccinations?
Influenza virus has a much higher mutation rate than varicella, leading to frequent antigen changes in the coat proteins and a corresponding deficit of memory cells.
Your initial version of the influenza assay kit was a great success. Now you are making a new version that will detect one specific strain of influenza that is particularly virulent, and distinguish it from other typical strains. What type of antibody would be best in this case?
You are designing a fast assay system for detecting flu virus in patients. You hope to send these tests to clinics in far-flung regions of the globe so they can conduct surveillance on influenza epidemics. The kits will need to remain functional for several years. The influenza virus is notorious for rapid mutation of envelope proteins. What type of antibody will you choose
You have a patient in your office who has the autoimmune disease systemic lupus erythematosus, which is being successfully treated using immunosuppressive drugs. Generally you recommend a yearly flu shot to your patients, which is available either in an injected, inactivated form or as a live, attenuated virus nasal spray. For this patient, what detail should you consider?
The injected, inactivated vaccine would be a better choice than the live attenuated nasal spray vaccine, since the patient is on immunosuppressive drugs.
A pathogenic virus has a new mutation in one of the coat proteins, that just happens to resemble the structure of a normal human protein present in dendritic cells of the central nervous system. What do you predict may be an outcome of infection by this virus?
The body's immune system will start attacking the brain cells because the viral protein is very similar to the protein on the dendritic cells.
B cells can generate antibodies with over 1010 different antigen-binding sites. How do so many different antibodies fit onto a single B cell?
They don't -- each B cell makes only a single variety of antibody.
Some scientists are trying to develop a vaccine that would prevent cancer. What is an important consideration?
Antigen selection would be critical, due to danger of the body's immune system attacking its own healthy tissue.
You are studying a trafficking protein important for secretion in helper T cells. What is the likely outcome of a defect in this protein?
impaired secretion of cytokines
T cells binding to MHC class I-peptide complexes are responsible for acceptance or rejection of transplanted organs. To facilitate acceptance of the transplant, the ideal donor will have a close genetic relationship with the recipient -- even then, immune suppression drugs are often necessary. In a strange variation of this phenomenon, the endangered Tasmanian devil of Australia suffers from a devastating disease in which tumorous tissue is transmitted from animal to animal. What is the likely explanation for the lack of rejection of this transmissable tumor?
Inbreeding in the small population has led to reduced genetic diversity and much-less variable MHC class I genes.
A patient has come to you for a second opinion. "I have these mysterious lumps in my right armpit," he says, "The other doctor says we may have to remove them. What do you think?"
You notice red scratches on the patient's right arm. "You must have a new kitten. Cat scratch disease, from the bacterium Bartonella ," you say, "And we certainly won't remove those lumps, they are really important! Those are your..."
"lymph nodes, where naive B and T cells encounter antigens and become activated."
Until renamed by Paul Ehrlich in the 1890s, the heat-labile, nonspecific part of the immune system that enhances inflammation was known as "alexin". We now know that various proteins of this system have a variety of functions, including bursting pathogens by insertion of a membrane-attack complex. What did Erhlich rename this specific part of the innate immune system?
the complement system
A young child is extremely susceptible to infections by a wide range of bacteria. A genome sequencing test determines that the boy has an inactivating mutation in a single gene. What is the most-likely candidate for the mutated gene?
a Toll-like receptor
What is the most fundamental difference between the innate immune system and the adaptive immune system?
the way in which pathogens are recognized
What is true regarding cytokines?
Cytokines are secreted by TH cells and bind to receptors.
Which of the following cells is matched to an incorrect function?
neutrophil—important antigen-presenting cell
What do we call a lymphocyte that has never encountered an antigen?
What is true regarding antigens?
A large antigen is likely to have many different epitopes, each of which can stimulate a distinct immune response.
A friend tells you the following story. "My aunt just received a heart transplant. Her doctors warned us that her body might reject the tissue. I just can't understand how that could happen as human hearts are made of the same tissues, aren't they?" How do you respond?
"Yes, all human hearts are made of cardiac muscle. But, most people have different MHC class I proteins on their cell surfaces. Your aunt's immune system can cause tissue rejection because of the 'nonself' MHC proteins on the donor heart."
Select the correct statement regarding the temperature response of the immune system.
After binding to a pathogen, macrophages release interleukin-1, which stimulates neurons in the hypothalamus to raise the body's temperature, producing a fever.
When a "new" antigen first challenges the immune system, if the primary immune response produces B cells, what are the fates of those B cells?
I-Some of the B cells become plasma cells that secrete antibodies.
II-Some of the B cells become memory cells and can produce a swifter response if the body encounters that particular antigen again.
III-Some of the B cells secrete chemicals called interleukins, which travel to the brain to induce a fever.
I and II
Some viral pathogens evade detection by the vertebrate immune system by a mechanism that most likely involves what process?
frequent changing of surface antigens
The ability of a vertebrate to generate millions of different lymphocytes is a result of its DNA undergoing what process?
Which part of the antibody molecule determines what epitope it binds to?
the two arms of the Y
What do cytotoxic T cells interact with?
MHC class I proteins and viral or cancer cell peptides
The cell-mediated immune response is brought about by which cells?
The human immunodeficiency virus mounts a direct attack on TH cells by recognizing the _______ proteins in the plasma membrane of these cells.
What is a necessary component of a powerful immune system?
an ability to distinguish self from nonself
What molecules are released by activated helper T cells
What category of cells includes both phagocytes and lymphocytes?
A patient with melanoma receives three types of therapy: surgery, radiation, and interferon. Which of these represents something the immune system uses against cancer as well?
Interferon -- T cells and natural killer cells secrete interferon in response to tumor cells
Which cells produce specific antibodies?
What cells are the precursors of macrophages?
What are the source of antibody-producing cells?
What cells directly stimulate the activity of other cells in the generation of an immune response?
What cells are phagocytes that can also present antigens to TH cells?
What is an iPS cell?
A cell that has been induced into a earlier stage thus making it pluripotent
Which researcher would be most accurately described as engaging in reproductive cloning?
Peter is trying to clone particularly large bull
Which researcher would be most accurately described as engaging in therapeutic cloning?
Ayame is working in a lab that is tryng to induce the formation of new skin cells
A cell that was capable of forming any type found in the organisms body but was not capable for forming the amniotic membrane would be __________.
This protein or protein complex functions in the cell to stop cell division if the cell has experienced extensive DNA damage:
You are leading a team of researchers at a pharmaceutical company. Your goal is to design drugs that help fight cancer. Specifically, you want to focus on drugs that bind to and inactivate certain proteins, thereby halting cell cycle progression. One of your team members suggests targeting the retinoblastoma (Rb) protein and inhibiting this protein. Will this approach be successful? Why or why not?
This approach will not be successful. Rb is tumor-suppressor protein, and functions to inhibit the action of a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would essentially create the same situation as in as a cell that lacks both copies of the Rb gene. Lack of Rb activity would release the inhibition of cell cycle regulatory proteins, thereby promoting cell cycle progression, rather than halting it.
If you were to think of the cell as a car, and mitosis as a process that drives that car to go, what would be a good analogy for a cell that has a mutation in both copies of a tumor-suppressor gene?
The brake pedal of a car does not work at all.
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