ECOL 409
Which of the following is an accurate statement of relationships? C is equally related to B and D. C is more closely related to D than to B. C is more closely related to B than to D. C is related to B, but not to D.
C is more closely related to D than to B.
According to the table below, the time since tigers and frogs have evolved from their most recent common ancestor, there has been a total of ____ nucleotide changes on these two evolutionary branches. Question options: 188 199 211 191
199
Which of the following is FALSE in regards to adaptive immunity and the evolutionary arms race between parasites and pathogens? Question options: Microbes have a shorter generation time, so will always win the pathogen-host arms race Rapid adaptive change can take place inside of one individual After infection, lymphocyte replication and mutation rates are amplified Vertebrates don't have evolve as quickly as microbes at the population level
Microbes have a shorter generation time, so will always win the pathogen-host arms race
In the depicted example phylogenetic tree of some vertebrates, what is the bootstrap proportion of the node that depicts the most recent common ancestor of humans and sea turtles?Fill in the bootstrap proportion on that node (a number). (This tree of vertebrates may look different from one you may have seen elsewhere. For the purposes of this question, assume this tree is accurate as depicted and base your answer on this tree only.)
100
Approximately what percentage of individuals infected with covid-19 lack any symptoms (i.e., are asymptomatic)? Question options: 1% 5% 10% 20%
20%
Which of the following attributes of covid-19 make it an especially challenging infectious disease for public health authorities to control? Question options: Human-to-human transmission Asymptomatic and pre-symptomatic transmission Relatively high R0 All of the above
all of the above
An infectious disease can best be defined as: Question options: any disease that stays within one particular host any disease any disease that causes severe symptoms in its host any disease that's caused by another organism
any disease that's caused by another organism
The Spanish flu and influenza viruses H5N1 and H7N9 (the two influenza viruses mentioned in Michael Worobey's seminar) all originated in what group of animals? Question options: avian reptilian mammalian simian
avian
In contrast to the covid-19 pandemic, the 1918 Spanish flu pandemic was characterized by: Question options: the massive movement of individuals deployed in the military back to their home countries. widespread communication between countries after the initial infections. major technological advances in vaccine development. the use of high-quality respirators (e.g., N95 masks).
the massive movement of individuals deployed in the military back to their home countries.
Natural selection is _______ mechanism(s) of evolution that results in adaptations that leads to an _______ average fitness of a population. Question options: the only; increased the only; decreased one of several; decreased one of several; increased
the only; increased
A "variant of concern" is one that is more infectious and more likely to cause breakthrough infections. Question options:TrueFalse
true
In both the 2009 swine flu and 1918 flu pandemics, one or more RNA segments of the circulating influenza strains had its origins in a non-human animal. Question options:TrueFalse
true
The 1918 Spanish flu severely impact young adults (peaking around ~28 years of age) because as children, these young adults: Question options: were exposed to a flu virus (H3 virus) closely related to the 1918 Spanish flu virus, which did not provide sufficient immunity. were never exposed to a flu virus. lived in an area of the United States that was isolated from the 1918 Spanish flu pandemic. were exposed to a flu virus (H3 virus) distantly related to the 1918 Spanish flu virus, which did not provide sufficient immunity.
were exposed to a flu virus (H3 virus) distantly related to the 1918 Spanish flu virus, which did not provide sufficient immunity.
Approximately how many people died worldwide in the 1918 influenza virus pandemic? Question options: ~ 500 ~ 5000 ~ 50,000 ~ 50 million
~ 50 million
In the lancet liver fluke example, snails were the Question options: definite host. intermediate host. primary host. None of these
intermediate host.
The main difference between the mRNA vaccines and the vector vaccines is the mRNA vaccine injects the mRNA sequence of the spike protein in a _______________ whereas the vector vaccine injects genes of the spike protein inside a _______________ to stimulate an immune response. Question options: inactive virus, active virus harmless virus, lipid nanoparticle lipid nanoparticle, harmless virus active virus, inactive virus
lipid nanoparticle, harmless virus
An obligate parasite ______ a host, while a facultative parasite ______ a host. Question options: requires; does not require does not require; requires
requires; does not require
What is a zoonosis? Question options: A virulent epidemic occurring in wildlife. An infection that is restricted to wildlife animals. An infection normally circulating in non-human animals that humans sometimes acquire via cross-species transmission events. An epidemic occurring in zoo animals.
An infection normally circulating in non-human animals that humans sometimes acquire via cross-species transmission events.
A strict consensus tree showing that a relationship between three taxa is uncertain would be drawn as a: Question options: Polytomous tree "Majority rule" tree Dichotomous tree Paraphyletic tree
Polytomous tree
In terms of genome organization, what type of viruses are retroviruses? Question options: Double stranded DNA (dsDNA) as genome Negative sensed, single stranded RNA (-ssRNA) as genome Single stranded DNA (ssDNA) as genome Positive sensed, single stranded RNA (+ssRNA) as genome, and at a certain phase the genomic RNA is reverse transcribed to DNA, which is inserted in the host genome.
Positive sensed, single stranded RNA (+ssRNA) as genome, and at a certain phase the genomic RNA is reverse transcribed to DNA, which is inserted in the host genome.
What is the role of proteasomes in T-cell mediated immune response? Question options: Proteasomes cleave proteins into small peptides that will be presented by MHC molecules on the cell surface. Proteasomes cleave precursor MHC proteins into mature MHC proteins Proteasomes undergo clonal selection and affinity maturation to specifically bind to epitopes Proteasomes present antigens on the cell surface.
Proteasomes cleave proteins into small peptides that will be presented by MHC molecules on the cell surface.
Which statement about protozoa is correct? Question options: Protozoa are a monophyletic group of eukaryotes. Protozoa are a monophyletic group of prokaryotes. Genetic diversity among animals is larger than genetic diversity among protozoa. Protozoa are a paraphyletic group of eukaryotes. Genetic diversity among plants is larger than genetic diversity among protozoa. Protozoa are a paraphyletic group of prokaryotes.
Protozoa are a paraphyletic group of eukaryotes.
Antigenic shift can best be described as: Question options: Recycled "garbage" virions into infectious viruses Variants of Cytotoxic T lymphocytes Point mutations that introduce new genes Reassortment of virus genome segments to create a new virus type
Reassortment of virus genome segments to create a new virus type
When transmission probability and virulence are positively coupled, which of the following would influence the level of virulence that is expected to eventually evolve? Question options: The mode of transmission of the infection. The level of virulence of the first strain that emerged in that host species. Whether the pathogen is a virus or a bacterium. When transmission probability and virulence are positively coupled, the level of virulence is always expected to evolve to an intermediate level that corresponds to a mortality rate of about 50%.
????, got this one wrong
Both the Spanish influenza virus of 1918 and the Coronavirus: Question options: A. are respiratory viruses. B. are from an animal source. C. have an infection fatality rate of 99%. D. A and B E. A, B, and C
A and B
Which of the following is NOT a region of the heavy chain of B-cell receptors? Question options: V (Variable) D (Diversity) J (Joining) B (B-cell)
B (B-cell)
Besides the literal definition of the basic reproductive number R0, what can R0be a measure of? Question options: A parasite's fitness. A parasite's virulence. A parasite's mutation rate. A parasite's intra-host replication rate.
A parasite's fitness.
In a flu patient, millions of virions of influenza A virus are present. They represent a diverse population inside a host. However, when the virus is transmitted to a new host, only a few hundred virions make it to the new host. What is this transmission event an example of? Question options: Evolution by natural selection. Gene flow. Positive selection. A population bottleneck.
A population bottleneck.
Covid-19 is caused by what kind of pathogen? Question options: A bacterium A positive-sense single-stranded RNA (+ssRNA) virus A double-stranded RNA (dsRNA) virus A double-stranded DNA (dsDNA) virus
A positive-sense single-stranded RNA (+ssRNA) virus
Which of the following inter-species interactions is NOT an example of antagonism? Question options: Cheetah hunting a gazelle. Panda bear eating bamboo plants. A vulture and a hyena both eating from one carcass. Myxoma virus infecting European rabbits.
A vulture and a hyena both eating from one carcass.
Covid-19 is primarily transmitted via: Question options: Direct person-to-person contact Surface tranmission Airborne particles Bodily fluids
Airborne particles
Which interpretation(s) of the comparison between this host and parasite phylogenetic tree from Moran & Bauman 1994 paper could be correct? Choose the best answer. Parasites and hosts are co-evolving and therefore their evolutionary lineages have been co-diverging too. Parasite lineages diverged whenever the lineages of their hosts diverged too. The evolutionary divergence of the parasite is linked to the evolutionary history of the host. All of the above could be correct.
All of the above could be correct.
What is a dead-end host? Question options: A host that the parasite is not adapted to infect. A host from which no or very limited onwards transmission occurs. A host in which the parasite "accidentally" winds up in. All of the above.
All of the above.
What is an appropriate definition of antigenic variation? Question options: Alterations in parasite proteins in order to avoid a host immune response Alterations in Toll like receptors to improve specificity of the immune response Alterations in B cell receptors to improve specificity of the immune response Alterations in T cell receptors to improve specificity of the immune response
Alterations in parasite proteins in order to avoid a host immune response
Which of the following could lead to cytotoxic T lymphocyte (CTL) escape? Question options: Impossible, an effective CTL response cannot be avoided Parasites replicating intracellularly in host cells Parasites having a mutation rate of 0 (zero). An amino acid substitution that leads to reduced binding of a parasite's peptide to MHC molecules
An amino acid substitution that leads to reduced binding of a parasite's peptide to MHC molecules
What is an endosymbiont? Choose the best definition. Question options: A prokaryotic symbiont. A symbiont of unicellular eukaryotes. A symbiont that is also a mutualist. An organism that lives inside a host body or cells.
An organism that lives inside a host body or cells.
In March 2014, a deadly outbreak of a hemorrhagic fever erupted in Guinea, but the causative agent was unknown. Genetic sequences of three patients were obtained, and were compared in a phylogenetic tree with representatives of filoviruses. Based on the information in this phylogenetic tree, write the full and exact name of the virus the unknown isolates are most closely related to.
Answer:Zaire ebolavirus
Which statement about bacteria is false? Question options: Bacteria can sometimes transfer hereditary material from one bacterial cell to the other. Bacteria, Archaea, and viruses are asexual organisms and therefore genetic recombination does not occur in these groups. Bacteria, Archaea, and Eukaryotes represent three separate Domains in the tree of life. A minority of bacteria living inside the human body are parasitic.
Bacteria, Archaea, and viruses are asexual organisms and therefore genetic recombination does not occur in these groups.
According to the virulence-transmission trade-off hypothesis and using this equation of the basic reproductive number, R0=����+�+��, why would decreasing virulence not necessarily lead to an increase in R0? Question options: Because the recovery rate v would decrease and the transmission probability β would increase. Because the host population size N would eventually decrease. Because virulence is not a component of this equation. Because the recovery rate v would increase and the transmission probability β would decrease.
Because the recovery rate v would increase and the transmission probability β would decrease.
Two bacterial species live together in Frank's oral cavity. Frank takes particular antibiotics, which kills off only one of the two species in his oral cavity. Bacterial cells of the remaining species now proliferate and occur in numbers 2 times higher than originally before the antibiotic treatment. What was the type of interaction the different bacteria species experienced with each other? Question options: There was no interaction between the two bacteria species Competition Commensalism Mutualism
Competition
What kind of inter-species interactions can members of the human microbiome experience? Question options: Parasitism, mutualism, and commensalism; but no competition. Only mutualism. Competition, parasitism, and commensalism; but no mutualism. Competition, mutualism, commensalism, and parasitism.
Competition, mutualism, commensalism, and parasitism.
What is the basis of antigenic variation in fast-evolving viruses such as HIV and hepatitis C? Question options: Differential expression of different surface glycoprotein genes Differential expression of different polymerase genes Continuous molecular evolution Somatic recombination
Continuous molecular evolution
How can a doctor measure progression of AIDS in a patient infected with HIV-1? Question options: Counting the number of macrophages Counting the number of cytotoxic T cells Counting the number of CD4 T cells Counting the number of PAMPs
Counting the number of CD4 T cells
Which of the following cell types can kill cells that present antigens via MHC on their cell surface? Question options: Helper T cells Cytotoxic T cell B cells Macrophages
Cytotoxic T cell
For which of the following receptor proteins do the corresponding genes undergo somatic recombination? Question options: T-cell receptor Toll-like receptor H-cell receptor Antibody receptor
T-cell receptor
A parasite is: Question options: A. An organism that causes a disease (e.g, inflicts harm). B. An organism literally "living in its food". C. Any organism that lives inside a host. D. A and B E. A, B, and C
D. A and B
Fungi are: Question options: A. heterotrophic. B. saprophytic. C. photosynthetic. D. A and B E. A, B, and C
D. A and B
What did the discoveries of DRC60 and ZR59 samples suggest? A. HIV-1 was already well established by 1960. B. HIV-1 group M has been circulating in people for over a century. C. HIV-1 has low levels of diversity. D. A and B E. A, B, and C
D. A and B
One of the goals of "flattening the curve" early in the covid-19 pandemic was to: Question options: Decrease the R0 Increase the R0 Leave the R0 unchanged
Decrease the R0
Which of the following is an appropriate explanation for the large diversity of lymphocyte receptors? Question options: A human individual carries millions of different alleles of the genes that encode for lymphocyte receptors The lymphocyte receptors are post-translationally modified to different shapes Diversity is generated largely by somatic recombination of the genes that encode for lymphocyte receptors A human individual carries millions of different genes that encode for lymphocyte receptors
Diversity is generated largely by somatic recombination of the genes that encode for lymphocyte receptors
A definite host is often the host in which: Question options: A. reproduction occurs. B. does not require medical attention. C. requires medical attention. D. A and B E. A and C
E. A and C
A patient with a bacterial infection is treated with penicillin (a type of antibiotic). Most bacteria immediately die from the antibiotic treatment, but some cells carry a mutation that ensures they are resistant to the antibiotic. The number of resistant bacteria soon becomes much higher than the number of antibiotic-susceptible bacteria in this patient. What is this process called? Question options: Evolution by gene flow Evolution by genetic drift Evolution by natural selection Evolution by founder effect
Evolution by natural selection
According to Dr. Michael Worobey, the January patient detected in Washington was the source ("patient zero") of the covid-19 epidemic in United States. Question options: True False
False
Cancer is hereditary or environmental, so it cannot be transmitted directly between individuals.
False
If you're vaccinated and test positive for covid-19, the CDC guidance suggests you do not need to self-isolate. Question options:TrueFalse
False
The body shape that characteristics helminths and the ability to parasitize evolved once in evolutionary history. Question options:TrueFalse
False
The primary difference between an unrooted tree and a rooted tree is that an unrooted tree has an explicit direction of evolutionary time. Question options:TrueFalse
False
What is the meant by there is a "fundamental asymmetry of sex"? Question options: Male reproduction is mainly limited by access to resources Female reproduction is mainly limited in by access to males Males invest more energy in reproduction Females invest more energy in reproduction
Females invest more energy in reproduction
When a subset of individuals immigrate to a new area and establish a new population, this is called: Question options: Founder Effect Natural Selection Gene Flow Artificial Selection
Founder Effect
Consider this published phylogenetic tree of HIV-1 (Human Immunodeficiency Virus) strains M/A, M/B, N and O, and several SIVcpz strains (Simian Immunodeficiency Virus of chimpanzees). Don't mind the colors. Which of the following is an accurate statement? Question options: All SIVcpz strains form a monophyletic group together. HIV-1 is a paraphyletic group. All HIV-1 strains form a monophyletic group together. HIV-1 M/A and HIV-1 M/B are paraphyletic.
HIV-1 is a paraphyletic group.
Which of the following is a way in which fitness (in the evolutionary sense) can be estimated? Question options: How long an individual survives after it is done reproducing. The total number of individuals of a species. Fitness cannot be measured, it is an abstract quantity. How many offspring an individual produces.
How many offspring an individual produces.
In which situation could virulence be an adaptive trait? Question options: If the pathogen is only pathogenic when it is spilled over into a different host species. If transmission probability and virulence are positively coupled. When the basic reproductive number R0 is solely determinable by this equation: �0=���+�+� In none of the above.
If transmission probability and virulence are positively coupled.
A mutation in a virus arises that changes the amino-acid sequence of a viral protein that contains the dominant epitope for the host's CTL mediated immunity. In which of the following situations would this lead to CTL escape? Question options: If the affinity of TCR binding is reduced with the new epitope. If the processing of peptides in the proteasome is affected with the new viral protein. If the efficiency of binding to MHC molecules is reduced with the new epitope. In all of the above situations.
In all of the above situations.
What is an opportunistic infection? Question options: Infection caused by organisms that for all or most of their life cycle are parasitic. Infection caused by organisms that are often facultatively parasitic and invade hosts with weakened immune systems. Infection caused by organisms that are obligatory parasitic and invade hosts with weakened immune systems. Infection caused by organisms that are able to invade hosts with particularly well functioning immune systems.
Infection caused by organisms that are often facultatively parasitic and invade hosts with weakened immune systems.
Which of the following would provide evidence that a parasite and its host have co-evolved? Question options: When the parasite is transmitted via "cultural vectors". The parasite is highly virulent for its host. The phylogenetic tree of the parasite differs significantly from the phylogenetic tree of the host. Infectivity is higher when a host is challenged in the lab with parasites from the same year, than when challenged with parasites revived from the previous year or from the subsequent year.
Infectivity is higher when a host is challenged in the lab with parasites from the same year, than when challenged with parasites revived from the previous year or from the subsequent year.
What is a major goal of evolution? Question options: There are no goals in evolution. Produce healthy organisms. Remove unwanted alleles. Produce larger animals, like mammals, with large brains.
There are no goals in evolution.
Which of the following is a reason why people need to get a new and different flu shot (vaccine) every year to remain protected from influenza? Question options: All vaccines need to be administered yearly to be effective Influenza virus continuously evolves and as such evades immune recognition via antigenic drift Scientists still have not found a good influenza vaccine so are trying out different vaccine types each year Currently known influenza virus vaccines are not able to lead to immunological memory against any influenza virus strain
Influenza virus continuously evolves and as such evades immune recognition via antigenic drift
Which of the following is a correct function of the CD4 protein on T cells? Question options: It binds to Toll-like receptors It binds to CD8 It binds to PAMPs It binds to MHC class II molecules
It binds to MHC class II molecules
How long did it take for scientists to identify, culture, and sequence the SARS-CoV-2 virus? Question options: Less than a month Several months About a year This information is still unknown
Less than a month
Consider the following population of grasshoppers: 20% have a green color, 50% have a brown color and 30% have red color. This year has been a great year for the grasshopper population: no predators and as much food available as they can eat. All grasshoppers are able to reproduce and all individuals have 2 offspring each. Which of the following statements is CORRECT: Question options: Fitness for each individual has doubled. These high levels of reproduction will lead to high levels of sexual selection. Natural selection for a particular color will not occur because there was no variation in fitness among individuals with different colors. These high levels of survival will lead to high levels of natural selection.
Natural selection for a particular color will not occur because there was no variation in fitness among individuals with different colors.
Exponential growth occurs when: Question options: Numbers double at fixed intervals. Numbers triple at fixed intervals. Numbers quadruple at fixed intervals. Numbers plateau at fixed intervals.
Numbers double at fixed intervals.
What was the source of the cholera outbreak in Haiti in 2010? Question options: Ruptured wastewater treatment plant Failed sewage system Contaminated aquifer Peacekeepers sent for aid relief
Peacekeepers sent for aid relief
Which of the following statements is true? Question options: One macrophage carries over a million different types of PAMP-recognizing receptors One macrophage carries a single type of PAMP-recognizing receptor One lymphocyte carries many different types of antigen-recognizing receptors One lymphocyte carries a single type of antigen-recognizing receptor
One lymphocyte carries a single type of antigen-recognizing receptor
Why can we make an analogy between this quote in an Alice in Wonderland book ("Now, here, you see, it takes all the running you can do, to keep in the same place") by the Red Queen character, and an evolutionary arms race between antagonists? Question options: Co-evolution in antagonistic interactions is restricted to fast-evolving species. Organisms in an antagonistic interaction need to keep on evolutionarily changing to be able to survive in an ever-evolving environment, while the interaction can remain antagonistic through time. The evolutionary arms race is not observable on the phenotypic level. It is a an analogy for the faster running skills that predators and prey evolve.
Organisms in an antagonistic interaction need to keep on evolutionarily changing to be able to survive in an ever-evolving environment, while the interaction can remain antagonistic through time.
Which of the following was NOT mentioned as one of the characteristics that affects animals as parasites? Question options: They often have an obligatory sexual reproduction phase. They have a large genome, so evolutionary time scales are slower. They are multicellular and large, so they are always extracellular parasites. Some animals are unicellular, and they are always intracellular parasites.
Some animals are unicellular, and they are always intracellular parasites.
Why was the 1918 pandemic named the "Spanish flu"? Question options: The cases in Spain were the most virulent. The first cases originated in Spain. Spain did not censor news about the virus. Spanish people were immune from the virus.
Spain did not censor news about the virus
Humans harbor an immense diversity of bacteria in their microbiomes. One of these is bacteria species A. Which of the following describes a commensalistic interaction between humans and bacteria species A? Question options: Species A receives food from the food ingested by its human host and requires the human gut to live in, but Species A also causes a severe disease of the human intestine. Species A receives food from the food ingested by its human host and requires the human gut to live in, but Species A also breaks down large protein molecules in human food so that humans can more easily absorb amino acids and make use of them. Species A receives food from the food ingested by its human host and requires the host gut to live in, but Species A has no effect on its human host. None of the above describe a commensalistic interaction.
Species A receives food from the food ingested by its human host and requires the host gut to live in, but Species A has no effect on its human host.
In LCMV infection in lab mice, a single Y to F substitution in the epitope KAVYNFATM leads to a 100-fold reduction in affinity with the dominant T cell receptor. What is the consequence of this? Question options: The ability of the dominant cytotoxic T cells to bind to that epitope will be reduced. The ability of MHC proteins to undergo somatic recombination will be reduced. There is no consequence because immune response against viruses is primarily mediated by B cells. The cytotoxic T cell response will be 100 times stronger.
The ability of the dominant cytotoxic T cells to bind to that epitope will be reduced.
What is an evolutionary explanation for mutualism? Question options: It is the product of short-sighted evolution. The benefit of receiving a service from a partner outweighs the cost of performing a service for a partner. The type of service each partner is providing is exactly the same as the service they are receiving so it balances out. In the end evolution leads to peaceful coexistence between species.
The benefit of receiving a service from a partner outweighs the cost of performing a service for a partner.
What is the basic reproductive number R0? Question options: The expected number of secondary cases produced by a single infected individual in a susceptible host population. The number of offspring a parasite produces. The number of people that are not vaccinated for a particular infection. The expected number of secondary cases produced by a single infected individual in a susceptible host population PER DAY.
The expected number of secondary cases produced by a single infected individual in a susceptible host population.
When could an epidemic stop and die out? Question options: When R0 < 1. In none of the listed situations. When the number of susceptible people is higher than a certain threshold. When R0 > 1.
When R0 < 1.
In which of these situations could virulence of a pathogen in humans expected to be a coincidence and not an adaptive trait? Question options: The pathogen and humans have co-evolved. The pathogen is usually transmitted among a different host species. There is an evolutionary trade-off between virulence and transmission in humans. The pathogen's virulence is coupled to better transmission efficiency in humans.
The pathogen is usually transmitted among a different host species.
Which of the following is an appropriate definition for immunological memory? Question options: The mechanism by which an organism prevents exposure to microbes. The mechanism by which an organism prevents development of an immune response against the hosts' own tissues. The persistence of pathogen-specific antibodies and lymphocytes after the original infection has been eliminated so that reinfection can be prevented. The process of reducing or eliminating a pathogen.
The persistence of pathogen-specific antibodies and lymphocytes after the original infection has been eliminated so that reinfection can be prevented.
Why does genetic drift have a greater effect on smaller populations than on larger populations? Question options: Individuals from smaller populations are more likely to migrate and found a new population. Individuals in populations already have a low fitness. Selection pressure is stronger in small populations. The probability that allele frequencies, especially of rare alleles, change by chance during genetic drift is greater in small populations.
The probability that allele frequencies, especially of rare alleles, change by chance during genetic drift is greater in small populations.
Which of the following is an appropriate definition of clonal deletion? Question options: The removal through apoptosis of B cells and T cells that have expressed receptors for self molecules After full maturation and amplification of B and T cells, the removal of unnecessary clones Deletion of random DNA stretches in the genes encoding for lymphocyte receptors The removal through apoptosis of B and T cells that are identical to each other
The removal through apoptosis of B cells and T cells that have expressed receptors for self molecules
How does a virus start to infect a host cell? Question options: Viruses never infect host cells, they remain extracellular. The virus forms specific molecular bonds with particular host cell surface proteins. The virus membrane fuses with the first host cell membrane it encounters. The virus replicates massively outside the host cell after which many virus particles invade the host cell together.
The virus forms specific molecular bonds with particular host cell surface proteins.
When you determine the sequence of the MHC class I B gene (also called HLA-B) in two different persons, it is possible you find four different DNA sequences. How is this possible? Question options: This is actually not possible, the same HLA gene will always have the same DNA sequence in different individuals. There are many different HLA-B alleles circulating in the human population and many people are heterozygous in this gene. There are many different splicing variants of HLA-B protein. Through somatic recombination HLA-B gene sequences will differ between people.
There are many different HLA-B alleles circulating in the human population and many people are heterozygous in this gene.
Why are homologous traits similar? Question options: They are derived from a common ancestor They are the result of convergent evolution They are derived from different ancestors They are acquired traits that can be inherited
They are derived from a common ancestor
Which characteristic is common among protozoa with few exceptions? Question options: Most are parasitic. They tend to live in moist habitats. They are mostly photosynthetic. They are sessile.
They tend to live in moist habitats.
What part of the phylogenetic tree does this arrow point to? Internal node Root Branch Tip
Tip
A doorknob is an example of a fomite. Question options:TrueFalse
True
Intermediate hosts can also be vectors. Question options:TrueFalse
True
The initial SARS-CoV-2 lockdown was the largest quarantine in human history, including the 1918 Spanish flu pandemic. Question options: True False
True
Viruses function based on the concept of immunological memory. Question options:TrueFalse
True
Which of the following is NOT an example of indirect transmission? Question options: Airborne transmission Vector-borne transmission Vertical transmission Fomite-borne
Vertical transmission
Which of the following are components of the virulence-transmission tradeoff hypothesis? Select all that apply. Question options: Virulence is an unavoidable cost to the pathogen for using the host resources for replication. Through increased mortality rates, high virulence can decrease transmission rate. Lower levels of virulence will always be favored by natural selection. An intermediate level of virulence is expected to evolve under the virulence-transmission tradeoff hypothesis.
Virulence is an unavoidable cost to the pathogen for using the host resources for replication. Through increased mortality rates, high virulence can decrease transmission rate. An intermediate level of virulence is expected to evolve under the virulence-transmission tradeoff hypothesis.
What does herd immunity mean? Question options: The situation in which the number of susceptible people becomes so large that the infection cannot spread. When enough people are vaccinated against a particular infection, so that the number of susceptible people becomes so small that the infection cannot spread. When people are already immune against a particular infection so that vaccination is not necessary. When 100% of the population and no less are vaccinated against a particular infection.
When enough people are vaccinated against a particular infection, so that the number of susceptible people becomes so small that the infection cannot spread.
Considering the case study example of the Zaire ebola virus epidemic, select the correct statement. Question options: Zaire ebola virus does not occur in human populations. Zaire ebola virus epidemics most often last for more than 10 years. Zaire ebola virus has been uninterruptedly circulating in humans since 1976. Zaire ebola virus epidemics always die out.
Zaire ebola virus epidemics always die out.
Which disease is described here? Each time this disease arises it is an independent evolutionary process in which multiple clones of cells originate through mutation and then compete with each other for resources.Clonal competition fed by genetic heterogeneity among cell clones drives natural selection that favours the better performing clones.Here performance significantly includes both the ability of cells to spread and invade other tissues and the resistance of some clones to chemotherapy.Thus two of the most significant characteristics of this disease are products of natural selection. Question options: diabetes AIDS multiple sclerosis cancer Alzheimer's disease
cancer
Constructing an alignment of genetic sequences allows for: Question options: a. Directly comparing the specific nucleotide differences between pairs of sequences. b. Ordering sequences so each vertical column represents a homologous site. c. Calculating the number of nucleotide differences between pairs of sequences. d. A and B e. A, B, and C
e. A, B, and C