Mastering Biology - Chapter 23
B) Sickle cell disease and malaria are both potentially lethal diseases. Though malaria is an infectious disease and sickle cell disease is inherited, both can cause life-threatening conditions.
Compare sickle cell disease and malaria. A) Sickle cell disease and malaria are both infectious diseases. B) Sickle cell disease and malaria are both potentially lethal diseases. C) Sickle cell disease and malaria are both genetic diseases. D) Sickle cell disease and malaria are both inherited diseases.
B) No. The expected genotype frequencies are A1A1 0.553; A1A2 0.381; A2A2 0.066. The expected genotype frequencies are significantly different from those expected from the Hardy-Weinberg Principle.
For a gene suspected of causing hypertension in humans, you observe the following genotype frequencies: A1A1 0.574; A1A2 0.339; A2A2 0.087. Is this gene in Hardy-Weinberg equilibrium? Why or why not? (Assume that a difference of three percent or more in any of the observed versus expected frequencies is statistically significant.) A) No. The expected genotype frequencies are A1A1 0.553; A1A2 0.381; A2A2 0.166. B) No. The expected genotype frequencies are A1A1 0.553; A1A2 0.381; A2A2 0.066. C) Yes. The expected genotype frequencies are A1A1 0.574; A1A2 0.339; A2A2 0.087. D) Yes. The expected genotype frequencies are A1A1 0.553; A1A2 0.381; A2A2 0.066.
A) It increases genetic diversity by introducing alleles from one population into another. Gene flow is the movement of alleles between populations.
How might gene flow be important in managing an endangered population? A) It increases genetic diversity by introducing alleles from one population into another. B) It is not important to managing an endangered species. C) It increases genetic diversity by introducing new genes into the DNA of a population. D) It decreases genetic diversity via the loss of alleles due to inbreeding depression.
A) The person is homozygous at the hemoglobin locus. C) The person is susceptible to malaria. A person with two copies of any allele is homozygous. A person with two normal copies of the hemoglobin allele is more susceptible to malaria than someone with a sickle cell hemoglobin allele.
If a person has two normal copies of the hemoglobin allele, which statements are true? Select all that apply. A) The person is homozygous at the hemoglobin locus. B) The person is heterozygous at the hemoglobin locus. C) The person is susceptible to malaria. D) The person is protected against malaria.
E) Decreased genetic difference between the two populations
Which of the following is the most predictable outcome of increased gene flow between two populations? A) Lower average fitness in both populations B) Higher average fitness in both populations C) Increased genetic difference between the two populations D) Increased genetic drift E) Decreased genetic difference between the two populations
B) Refuse glucose
Glucose is generally phagostimulatory (stimulates eating) for animals. The observation that cockroach populations exposed to poison + glucose bait began to refuse to eat glucose brings up the question of whether this aversion behavior is learned or whether it originated as a genetic mutation that became more common in the population over generations. To answer this question, you can make use of some simple genetic crosses to look for predicted inheritance patterns. Only genetic traits, rather than learned behaviors, would be expected to show the predicted patterns. First, you need to find two populations of pure-breeding cockroaches: one population that has been exposed to poison + glucose bait and exhibits the glucose-aversion behavior one population that has not been exposed to poison + glucose bait and does not refuse to eat glucose (wild-type) Next you perform a hybrid cross in which you mate together members from each of the two populations to create F1 offspring. Hypothesis: Glucose aversion is a genetically-determined dominant trait Prediction: If true then the F1 offspring will ________. A) Have an intermediate amount of aversion B) Refuse glucose C) Eat glucose D) Have a mix of aversion and non-aversion
A) Have an intermediate amount of aversion
Glucose is generally phagostimulatory (stimulates eating) for animals. The observation that cockroach populations exposed to poison + glucose bait began to refuse to eat glucose brings up the question of whether this aversion behavior is learned or whether it originated as a genetic mutation that became more common in the population over generations. To answer this question, you can make use of some simple genetic crosses to look for predicted inheritance patterns. Only genetic traits, rather than learned behaviors, would be expected to show the predicted patterns. First, you need to find two populations of pure-breeding cockroaches: one population that has been exposed to poison + glucose bait and exhibits the glucose-aversion behavior one population that has not been exposed to poison + glucose bait and does not refuse to eat glucose (wild-type) Next you perform a hybrid cross in which you mate together members from each of the two populations to create F1 offspring. Hypothesis: Glucose aversion is a genetically-determined incompletely dominant trait Prediction: If true then the F1 offspring will ________. A) Have an intermediate amount of aversion B) Refuse glucose C) Eat glucose D) Have a mix of aversion and non-aversion
C) Eat glucose
Glucose is generally phagostimulatory (stimulates eating) for animals. The observation that cockroach populations exposed to poison + glucose bait began to refuse to eat glucose brings up the question of whether this aversion behavior is learned or whether it originated as a genetic mutation that became more common in the population over generations. To answer this question, you can make use of some simple genetic crosses to look for predicted inheritance patterns. Only genetic traits, rather than learned behaviors, would be expected to show the predicted patterns. First, you need to find two populations of pure-breeding cockroaches: one population that has been exposed to poison + glucose bait and exhibits the glucose-aversion behavior one population that has not been exposed to poison + glucose bait and does not refuse to eat glucose (wild-type) Next you perform a hybrid cross in which you mate together members from each of the two populations to create F1 offspring. Hypothesis: Glucose aversion is a genetically-determined recessive trait Prediction: If true then the F1 offspring will ________. A) Have an intermediate amount of aversion B) Refuse glucose C) Eat glucose D) Have a mix of aversion and non-aversion
D) Have a mix of aversion and non-aversion
Glucose is generally phagostimulatory (stimulates eating) for animals. The observation that cockroach populations exposed to poison + glucose bait began to refuse to eat glucose brings up the question of whether this aversion behavior is learned or whether it originated as a genetic mutation that became more common in the population over generations. To answer this question, you can make use of some simple genetic crosses to look for predicted inheritance patterns. Only genetic traits, rather than learned behaviors, would be expected to show the predicted patterns. First, you need to find two populations of pure-breeding cockroaches: one population that has been exposed to poison + glucose bait and exhibits the glucose-aversion behavior one population that has not been exposed to poison + glucose bait and does not refuse to eat glucose (wild-type) Next you perform a hybrid cross in which you mate together members from each of the two populations to create F1 offspring. Hypothesis: Glucose aversion is a learned behavior Prediction: If true then the F1 offspring will ________. A) Have an intermediate amount of aversion B) Refuse glucose C) Eat glucose D) Have a mix of aversion and non-aversion
180
How can you determine if the glucose-aversion trait becomes more common in a cockroach population as a result of adaptive evolution? Part complete Exterminators have observed that their hydramethylnon-corn syrup baits initially work for attracting cockroaches, but the effectiveness lessens over time. Does this mean that the aversion trait evolves in the cockroach populations exposed to the bait? To answer this question, you need to identify a population of cockroaches with which you can perform an experiment. The experiment should be set up like this: 1. Observe and record the behavior of naïve cockroaches (never exposed to hydramethylnon) in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. These represent the initial frequencies of wild type glu+ and mutant glu- alleles in the population. 2. Treat the cockroach population's environment with hydramethylnon + glucose bait for 5 years. 3. After 5 years (about 15 generations), observe and record exposed cockroach behavior in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. 4. Determine if the population of cockroaches exposed to hydramethylnon + glucose is at Hardy-Weinberg equilibrium, or if exposure to hydramethylnon + glucose caused a shift in allele frequencies in the population. At the start of your experiment, suppose that you observed the genotypic distribution (based on phenotypic observations) shown in the table below in a naïve group of cockroaches in an infested apartment. The genotype (phenotype) is glu+/glu+ (glucose-attracted) There are 90 individuals in the original population. How many glu+ alleles are there?
7
How can you determine if the glucose-aversion trait becomes more common in a cockroach population as a result of adaptive evolution? Part complete Exterminators have observed that their hydramethylnon-corn syrup baits initially work for attracting cockroaches, but the effectiveness lessens over time. Does this mean that the aversion trait evolves in the cockroach populations exposed to the bait? To answer this question, you need to identify a population of cockroaches with which you can perform an experiment. The experiment should be set up like this: 1. Observe and record the behavior of naïve cockroaches (never exposed to hydramethylnon) in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. These represent the initial frequencies of wild type glu+ and mutant glu- alleles in the population. 2. Treat the cockroach population's environment with hydramethylnon + glucose bait for 5 years. 3. After 5 years (about 15 generations), observe and record exposed cockroach behavior in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. 4. Determine if the population of cockroaches exposed to hydramethylnon + glucose is at Hardy-Weinberg equilibrium, or if exposure to hydramethylnon + glucose caused a shift in allele frequencies in the population. At the start of your experiment, suppose that you observed the genotypic distribution (based on phenotypic observations) shown in the table below in a naïve group of cockroaches in an infested apartment. The genotype (phenotype) is glu+/glu- (intermediate) There are 7 individuals in the original population. How many glu+ alleles are there?
0
How can you determine if the glucose-aversion trait becomes more common in a cockroach population as a result of adaptive evolution? Part complete Exterminators have observed that their hydramethylnon-corn syrup baits initially work for attracting cockroaches, but the effectiveness lessens over time. Does this mean that the aversion trait evolves in the cockroach populations exposed to the bait? To answer this question, you need to identify a population of cockroaches with which you can perform an experiment. The experiment should be set up like this: 1. Observe and record the behavior of naïve cockroaches (never exposed to hydramethylnon) in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. These represent the initial frequencies of wild type glu+ and mutant glu- alleles in the population. 2. Treat the cockroach population's environment with hydramethylnon + glucose bait for 5 years. 3. After 5 years (about 15 generations), observe and record exposed cockroach behavior in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. 4. Determine if the population of cockroaches exposed to hydramethylnon + glucose is at Hardy-Weinberg equilibrium, or if exposure to hydramethylnon + glucose caused a shift in allele frequencies in the population. At the start of your experiment, suppose that you observed the genotypic distribution (based on phenotypic observations) shown in the table below in a naïve group of cockroaches in an infested apartment. The genotype (phenotype) is glu-/glu- (glucose-averse) There are 3 individuals in the original population. How many glu+ alleles are there?
187
How can you determine if the glucose-aversion trait becomes more common in a cockroach population as a result of adaptive evolution? Part complete Exterminators have observed that their hydramethylnon-corn syrup baits initially work for attracting cockroaches, but the effectiveness lessens over time. Does this mean that the aversion trait evolves in the cockroach populations exposed to the bait? To answer this question, you need to identify a population of cockroaches with which you can perform an experiment. The experiment should be set up like this: 1. Observe and record the behavior of naïve cockroaches (never exposed to hydramethylnon) in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. These represent the initial frequencies of wild type glu+ and mutant glu- alleles in the population. 2. Treat the cockroach population's environment with hydramethylnon + glucose bait for 5 years. 3. After 5 years (about 15 generations), observe and record exposed cockroach behavior in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. 4. Determine if the population of cockroaches exposed to hydramethylnon + glucose is at Hardy-Weinberg equilibrium, or if exposure to hydramethylnon + glucose caused a shift in allele frequencies in the population. At the start of your experiment, suppose that you observed the genotypic distribution (based on phenotypic observations) shown in the table below in a naïve group of cockroaches in an infested apartment. There are 100 individuals in the original population. How many glu+ alleles are there?
p=0.94, The sum total of all alleles in a population is known as its gene pool, and the allele frequency is a measure of the proportion of each allele in the gene pool.
How can you determine if the glucose-aversion trait becomes more common in a cockroach population as a result of adaptive evolution? Part complete Exterminators have observed that their hydramethylnon-corn syrup baits initially work for attracting cockroaches, but the effectiveness lessens over time. Does this mean that the aversion trait evolves in the cockroach populations exposed to the bait? To answer this question, you need to identify a population of cockroaches with which you can perform an experiment. The experiment should be set up like this: 1. Observe and record the behavior of naïve cockroaches (never exposed to hydramethylnon) in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. These represent the initial frequencies of wild type glu+ and mutant glu- alleles in the population. 2. Treat the cockroach population's environment with hydramethylnon + glucose bait for 5 years. 3. After 5 years (about 15 generations), observe and record exposed cockroach behavior in a paired dish experiment using food with glucose and food without glucose. Record the number of cockroaches exhibiting the three phenotypes: glucose-attracted, intermediate, and glucose-averse. 4. Determine if the population of cockroaches exposed to hydramethylnon + glucose is at Hardy-Weinberg equilibrium, or if exposure to hydramethylnon + glucose caused a shift in allele frequencies in the population. At the start of your experiment, suppose that you observed the genotypic distribution (based on phenotypic observations) shown in the table below in a naïve group of cockroaches in an infested apartment. What is the allele frequency?
A) He evaluated blood samples for malaria parasites and the presence of sickle cells. D) He expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected. Dr. Allison gathered blood samples from more than 5,000 children in East Africa. He analyzed the samples to identify malaria parasites and sickle cells. He found that children carrying the sickle cell character (or trait) had a lower parasite count, as if they were partially protected against malaria.
How did Dr. Allison test his hypothesis that sickle cell disease was connected to malaria? Select all that apply. A) He evaluated blood samples for malaria parasites and the presence of sickle cells. B) He looked for the underlying genetic mechanism causing sickle cell disease. C) He studied the way that the malaria parasite interacts with sickle cells. D) He expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected.
B) In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles. C) In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease. In different environments, natural selection favors different characteristics. In areas with malaria, the reproductive advantages of having one sickle cell allele (and some protection from malaria) kept the allele at high frequencies in the population. In areas without malaria, the reproductive disadvantages from sickle cell disease reduced the allele in populations.
How does Dr. Allison's work provide an example of natural selection in humans? Select all that apply. A) Natural selection caused the sickle cell allele to appear in east African populations. B) In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles. C) In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease. D) In areas with malaria, natural selection causes individuals to acquire the sickle cell allele as protection against malaria.
B) Homozygotes increase in frequency in the population over generations. Inbreeding increases homozygosity.
How does inbreeding alter genotype and allele frequencies? A) Dominant alleles become less prevalent in the population over generations. B) Homozygotes increase in frequency in the population over generations. C) Heterozygotes increase in frequency in the population over generations. D) There is no change in genotype frequency.
A) Support. Because the observed number of glucose-averse roaches is much higher than expected, you can conclude that the population is not in Hardy-Weinberg equilibrium. Therefore, the population must be evolving with regard to this trait. To make a more solid conclusion, you would do a statistical analysis to make sure the observed values were different enough from the expected values that they would not be due to chance alone.
If natural selection for this trait is not occurring, you would expect to see about the same genotype frequencies in all generations of the cockroaches. Below is a table of genotypes observed in 455 individuals after 5 years of exposure to hydramethylnon + glucose bait compared to those expected from predicted allele frequencies. If the observed values do not approximately match the expected values, then you have evidence that the population is going through adaptive evolution. What conclusion can you draw from these data? The data _______ the conclusion that the glucose-aversion trait has become more common in the population as a result of adaptive evolution A) Support B) Do not support
B) Much higher than. Because the observed number of glucose-averse roaches is much higher than expected, you can conclude that the population is not in Hardy-Weinberg equilibrium. Therefore, the population must be evolving with regard to this trait. To make a more solid conclusion, you would do a statistical analysis to make sure the observed values were different enough from the expected values that they would not be due to chance alone.
If natural selection for this trait is not occurring, you would expect to see about the same genotype frequencies in all generations of the cockroaches. Below is a table of genotypes observed in 455 individuals after 5 years of exposure to hydramethylnon + glucose bait compared to those expected from predicted allele frequencies. If the observed values do not approximately match the expected values, then you have evidence that the population is going through adaptive evolution. What conclusion can you draw from these data? The observed number of glucose-averse cockroaches is_________ than expected. A) Much lower than B) Much higher than
D) He hypothesized that there was a connection between malaria and sickle cell disease. On the basis of this hypothesis, Dr. Allison predicted high frequencies of sickle cell disease only in areas where malaria is common.
In 1949, Dr. Tony Allison observed a high frequency of Kenyans carrying the sickle cell allele in coastal areas and near Lake Victoria, but a lower frequency in the highlands. What did he hypothesize? A) He hypothesized that malaria causes sickle cell disease. B) He hypothesized that sickle cell disease was an environmental, not a genetic disease. C) He hypothesized that malaria is a genetic disease. D) He hypothesized that there was a connection between malaria and sickle cell disease.
A) Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population. People with one sickle cell allele are protected from malaria, but do not have sickle cell disease. Protection from malaria comes at the cost of more sickle cell disease in the population.
In some populations, 1 in 500 people have sickle cell disease. What reason does the film give for why a potentially deadly, inherited disease is found at such high frequencies? A) Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population. B) Individuals with two sickle cell alleles have an evolutionary advantage because they do not get sickle cell disease or get infected with malaria. C) Sickle cell alleles are new mutations and not enough time has gone by for these alleles to be eliminated from the population by natural selection. D) Individuals with two normal hemoglobin alleles get both sickle cell disease and are susceptible to malaria, so these alleles are eliminated from the population. Submit
A) 136, 65, 0.5 B) 118. 116, 1.0 C) 14, 92, 6.6 Notice how the relative fitness values change based on the type of food offered to the cockroaches in each treatment. Next you will use these relative fitness values to predict which genotypes will thrive under different conditions.
In the presence of poison-laced glucose, cockroaches that refuse glucose will have a much higher survival rate than cockroaches that feed indiscriminately. This explains why the glu- allele frequency increases over time in a population exposed to poison + glucose bait. However, energy from carbohydrates is required for growth and reproduction, and glucose is commonly found in non-poison foods that cockroaches encounter in human dwellings. By refusing to eat glucose, are glu-/glu- roaches missing out on an essential energy source? One way to answer this question is to measure the relative fitness of glu-/glu- roaches. Relative fitness is the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals. Relative fitness is affected by diet and environmental hazards. To determine the relative fitness of a particular genotype, you average the fitness values of a group of individuals with that genotype. Suppose you raise populations of each homozygous genotype in captivity with three different food sources (plus supplemental rat chow) and collect data about how many individuals survive from egg to adulthood (survivorship) and how many offspring each adult female produces over her lifetime (fecundity). The survivorship and fecundity data are shown in the table below. From this data, you can calculate fitness values. The absolute fitness of each genotype is calculated by multiplying the survivorship by the fecundity (only those individuals that survive will reproduce). The fitness of one relative to the other is the ratio of the two absolute fitness values. Use the following data to complete the table of fitness calculations. Convert percentage values to decimals before you do the calculations. Round absolute fitness values to the nearest whole number; round relative fitness values to one decimal place. The absolute fitness of glu+/glu+ (survivorship x fecundity), absolute fitness of glu-/glu- (survivorship x fecundity), and relative fitness of glu-/glu- to glu+/glu+ A) Food containing glucose, B) Food lacking glucose C) Hydramethylnon + corn syrup traps
A) The sickle cell allele will decrease in frequency. Without malaria, selection for the sickle cell allele decreases. As a result, the frequency will likely decrease.
Predict what will happen to the frequency of the sickle cell allele in areas where malaria has been eradicated. A) The sickle cell allele will decrease in frequency. B) The sickle cell allele frequency will not be affected. C) The sickle cell allele will increase in frequency.
A) glu-/glu- (glucose-averse) B) glu+/glu+ (glucose-attracted) C) glu-/glu- (glucose-averse) D) It's a tie - no winner As you have seen, the genotype with the greatest fitness depends on the environmental conditions. And as environmental conditions change, the allele frequencies and genotype frequencies in the population will fluctuate. This is the essence of adaptive evolution, not only in cockroaches but in every population of living things.
Suppose a large apartment complex is infested with cockroaches that have never been exposed to glucose-baited poison. A new tenant moves in and unknowingly brings along some stowaway glucose-averse cockroaches from her heavily-treated former apartment. These individuals escape the moving boxes and start reproducing in their new home, where they have to compete with the current resident cockroaches. Using the fitness values you calculated in the previous part, determine which genotype would "win" (that is, survive and reproduce more than the other) if the two genotypes had to compete for resources in the kitchens described below. (Assume that the traps are hydramethylnon + corn syrup traps.) The absolute fitness of glu+/glu+ (survivorship x fecundity), absolute fitness of glu-/glu- (survivorship x fecundity), and relative fitness of glu-/glu- to glu+/glu+ A) Food containing glucose: 136, 65, 0.5 B) Food lacking glucose: 118, 116, 1.0 C) Hydramethylnon + corn syrup traps: 14,92, 6.6 Who is the winner of the kitchen: A) With food items out, plus traps B) With food items out, no traps C) Clean, plus traps D) Clean, no traps
B) If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.
Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. If the human flu virus contributes a gene for Tamiflu resistance (Tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking Tamiflu, then what is most likely to occur? A) If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will increase in frequency. B) If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency. C) The new virus will maintain its Tamiflu-resistance gene, in case of future exposure to Tamiflu. D) The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment.
A) Roaches ate about the same amount from the dish with no hydramethylnon as they did from the control dish. B) Roaches ate about the same amount from the dish with no oleic acid as they did from the control dish. F) Roaches are refusing corn syrup.
To find out which ingredient the cockroaches are refusing, you can carry out a controlled experiment. Hydramethylnon is dissolved in oleic acid before being mixed with corn syrup to prepare the poisoned bait, so you should test all three ingredients. Suppose you conducted a feeding trial to test each ingredient. In the trial, a set of four agar dishes, three containing all except one ingredient and one with all three ingredients (the control), were weighed and placed 3 cm apart on the kitchen floor in an infested apartment. After two days, the dishes were weighed again to measure food consumption. You then repeated the trial 4 times and averaged the results. Based on the results of the feeding experiment, what conclusions can you draw? Select all that apply. A) Roaches ate about the same amount from the dish with no hydramethylnon as they did from the control dish. B) Roaches ate about the same amount from the dish with no oleic acid as they did from the control dish. C) Roaches ate about the same amount from the dish with no corn syrup as they did from the control dish. D) Roaches are refusing hydramethylnon. E) Roaches are refusing oleic acid. F) Roaches are refusing corn syrup.
A) Frequency-dependent selection
When imbalances occur in the sex ratio of sexual species that have two sexes (that is, other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of _____. A) Frequency-dependent selection B) Sexual selection C) Disruptive selection D) Stabilizing selection E) Balancing selection
B) No genetic drift can affect allele frequencies for the gene. Any condition that changes allele frequencies in the population represents a violation of the Hardy-Weinberg principle and means that the population will not be in Hardy-Weinberg equilibrium.
Which assumption must be correct for a population to be in Hardy-Weinberg equilibrium for a specific gene? A) The number of immigrants must equal the number of organisms emigrating. B) No genetic drift can affect allele frequencies for the gene. C) Natural selection must favor one phenotype. D)Mating must be nonrandom with respect to the gene.
C) The direction of evolutionary change due to genetic drift is random. Genetic drift is not driven by a directional effect but occurs as a magnification of chance effects due to small population size.
Which statement about genetic drift is correct? A) Genetic drift results from migration of new individuals into a population. B) Genetic drift becomes increasingly important with increasing population size. C) The direction of evolutionary change due to genetic drift is random. D) Genetic drift increases adaptation of individuals to their environment.
B) The cells that acquire these deleterious mutations are selected against by natural selection and these mutations are lost from the population over time.
Why don't the spontaneous deleterious mutations that occur in an individual E.coli cause downward drops in fitness in this population? See Section 23.6 (Page 475) . A) Deleterious mutations don't occur; the only mutations that occur are beneficial. B) The cells that acquire these deleterious mutations are selected against by natural selection and these mutations are lost from the population over time. C) Only deleterious mutations are lost by genetic drift in this population. D) Only beneficial mutations are fixed by genetic drift in this population.
B) Glucose aversion is an incompletely dominant trait. Glucose aversion is an incompletely dominant trait. You can tell this from the graph because the heterozygous F1 offspring consumed an intermediate amount of glucose compared to the parental cockroaches. The glu-/glu- parental cockroaches consumed less of the solution as the glucose concentration increased. The glu+/glu+ parental cockroaches consumed more of the solution as the glucose concentration increased. And the glu+/glu- F1 cockroaches consumed less of the solution as the glucose concentration increased, but still more than the glu-/glu- cockroaches. Neurophysiological studies of the glu-/glu- cockroaches' brains revealed that their glucose-sensing cells and bitter-sensing cells were inversely connected, leading them to perceive glucose as a bitter compound. In fact, these roaches spit glucose out when it is fed to them directly. Heterozygous glu+/glu- F1 cockroaches had a mix of normal and inversed sensing cells so that they tasted glucose as both sweet and bitter instead of one or the other.
You divide the roaches into four groups. Each group contains both types of parental roaches (glu-/glu- and glu+/glu+ ) and F1 roaches (glu-/glu+ ): Group 1 is fed a solution containing no glucose. Group 2 is fed a 100 mM glucose solution. Group 3 is fed a 300 mM glucose solution. Group 4 is fed a 500 mM glucose solution. Glucose itself is hard to measure in a cockroach, so a tracking dye needs to be added to the test solutions. After feeding, individual roaches are harvested, the dye is extracted from their bodies, and the amount of dye (representing the volume of glucose test solution ingested) is measured with a spectrophotometer. The results are shown in the graph below. Which hypothesis do these results support? A) Glucose aversion is a learned behavior. B) Glucose aversion is an incompletely dominant trait. C) Glucose aversion is a dominant trait. D) Glucose aversion is a recessive trait.
