which type of selection tends to increase genetic variation?

# which type of selection tends to increase genetic variation?

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Asked by 2 years ago
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Which of these individuals is a homozygous genotype?AA
All the genes in a population are that population's_____.gene pool
Genetic drift is a process based on _____.the role of chance
A mutation occurs when _____.there is a change in the DNA sequence of a gene
Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population?Alleles that promote "tallness" will decrease in frequency.
Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.genetic drift
The ease with which humans travel across the globe is likely to increase _____.gene flow
Homologous pairs of chromosomes are lined up independently of other such pairs during _____.metaphase I
Crossing over, resulting in an increase in genetic variation, occurs between _____.nonsister chromatids of homologous chromosomes
In human gamete production there is an average of _____ crossover events per chromosome pair.2-3
Which of these gametes contain one or more recombinant chromosomes?B,C,F, and G
The original source of all genetic variation is _____.mutation
Generation-to-generation change in the allele frequencies in a population is _____.microevolution
The evolutionary effects of genetic drift are greatest when _____.the population size is small
Rabbit ear size tends to decrease as latitude increases. This is an example of _____.a cline
According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.sexual reproduction
What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?founder effect
In evolutionary terms, an organism's fitness is measured by its _____.contribution to the gene pool of the next generation
Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____.directional selection
What is the only evolutionary mechanism that consistently leads to adaptive evolution?natural selection
How does diploidy help to preserve genetic variation?It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes.
Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations, which one most consistently requires a small population as a precondition for its occurrence?genetic drift
Which statement about variation is true?All geographic variation results from the existence of clines. All phenotypic variation is the result of genotypic variation. All nucleotide variability results in neutral variation. All genetic variation produces phenotypic variation (none of the above)
Which of the following is a true statement concerning genetic variation?It must be present in a population before natural selection can act upon the population.
Anopheles mosquitoes, which carry the malaria parasite, cannot live above elevations of 5,900 feet. In addition, oxygen availability decreases with higher altitude. Consider a hypothetical human population that is adapted to life on the slopes of Mt. Kilimanjaro in Tanzania, a country in equatorial Africa. Mt. Kilimanjaro's base is about 2,600 feet above sea level and its peak is 19,341 feet above sea level. If the incidence of the sickle-cell allele in the population is plotted against altitude (feet above sea level), which of the following distributions is most likely, assuming little migration of people up or down the mountain?B (steadily decreasing)
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. Which of the following represents the treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)?using moderate doses of NA and two different PIs at the same time for several months
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. Every HIV particle contains two RNA molecules. If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true?One of the RNA molecules has experienced gene duplication as the result of translocation.
Which variable is likely to undergo the largest change in value resulting from a mutation that introduces a new allele into a population at a locus for which all individuals formerly had been fully homozygous?average heterozygosity
In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary becauseheterozygotes can come about in two ways.
In the formula for determining a populations genotype frequencies, the pq in the term 2pq is necessary becauseheterozygotes have two alleles.
You sample a population of butterflies and find that 56% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population?Allele frequency cannot be determined from this information.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What proportion of the population is probably heterozygous (Aa) for this trait?0.50
You are studying three populations of birds. Population A has ten birds, of which one is brown (a recessive trait) and nine are red. Population B has 100 birds, of which ten are brown. Population C has 30 birds, and three of them are brown. In which population would it be least likely that an accident would significantly alter the frequency of the brown allele?Population B
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele?0.09
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals that are heterozygous for this allele?.32
Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasinggene flow
If the original finches that had been blown over to the Galpagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galpagos, this would have been an example ofgenetic drift and founder effect
You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is tocross your flies with flies from another lab.
Which of the following are basic components of the Hardy-Weinberg model?Frequencies of two alleles in a gene pool before and after many random matings.
Which of the following statements is not a part of the Hardy-Weinberg principle?The genotype frequencies in the offspring generation must add up to two.
True of false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.True
What is the frequency of the A1A2 genotype in a population compose of 20 A1A1 individuals, A1A2 individuals, and 100 A2A2 individuals?0.4
What is the frequency of the A1 allele in a population compose of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals?0.3
Which of the following evolutionary forces results in adaptive changes in allele frequencies?selection
What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p=0.8 and q=0.2 for a particular gene?The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively.
Which of the following evolutionary forces could create new genetic information in population?Mutation
Which type of selection tends to increase genetic variation?Disruptive selection
In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following?The value of a particular characteristic; characteristics of an organism can include such traits as size and color.
True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.False
Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?Directional selection
Women often have complication during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?Stabilizing selection
Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?Disruptive selection
Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?Stabilizing selection
The outcome of the conflict between bacteria and bacteriophage at any point in time results from A) frequency-dependent selection. B) evolutionary imbalance. C) heterozygote advantage. D) neutral variation. E) genetic variation being preserved by diploidy.A) frequency-dependent selection.
Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive): 1. Natural selection 2. Microevolution 3. Intrasexual selection 4. Evolution 5. Sexual selection A) 4, 1, 2, 3, 5 B) 4, 2, 1, 3, 5 C) 4, 2, 1, 5, 3 D) 1, 4, 2, 5, 3 E) 1, 2, 4, 5, 3C) 4, 2, 1, 5, 3
Sexual dimorphism is most often a result of A) pansexual selection. B) stabilizing selection. C) intrasexual selection. D) intersexual selection. E) artificial selection.D) intersexual selection.
During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation? A) Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations. B) Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations. C) There should be directional selection for bright red feathers in males. D) All three of these. E) Only B and C. dD) All three of these.
Most Swiss starlings produce four to five eggs in each clutch. Those producing fewer or more than this have reduced fitness. Which of the following terms best describes this? A) artificial selection B) directional selection C) stabilizing selection D) disruptive selection E) sexual selectionC) stabilizing selection
Heterozygote advantage should be most closely linked to which of the following? A) sexual selection B) stabilizing selection C) random selection D) directional selection E) disruptive selectionB) stabilizing selection
If the curve shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations, then which of these is (are) probably occurring? 1. immigration or emigration 2. directional selection 3. adaptation 4. genetic drift 5. disruptive selection A) 1 only B) 4 only C) 2 and 3 D) 4 and 5 E) 1, 2, and 3C) 2 and 3
The same gene that causes various coat patterns in wild and domesticated cats also causes the cross -eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations? A) Evolution is progressive and tends toward a more perfect population. B) Phenotype is often the result of compromise. C) Natural selection reduces the frequency of maladaptive genes in populations over the course of time. D) Polygenic inheritance is generally maladaptive, and should become less common in future generations. E) In all environments, coat pattern is a more important survival factor than is eye-muscle tone.B) Phenotype is often the result of compromise.
There are those who claim that the theory of evolution cannot be true because the apes, which are supposed to be closely related to humans, do not likewise share the same large brains, capacity for complicated speech, and tool-making capability. They reason that if these features are generally beneficial, then the apes should have evolved them as well. Which of these provides the best argument against this misconception? A) Advantageous alleles do not arise on demand. B) A populations evolution is limited by historical constraints. C) Adaptations are often compromises. D) Evolution can be influenced by environmental change.A) Advantageous alleles do not arise on demand.
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?If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.
Which statement correctly describes the role of chance in evolution?The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA.
You read about soapberry bugs and select the correct statement describing relative fitness in these individuals.A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age.
One out of 10,000 babies born in North America is affected by cystic fibrosis, a recessive condition. Assuming that the North American human population is in Hardy-Weinberg equilibrium for this trait, what percentage of the population is heterozygous for this trait? (Remember the equation for a population in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1.)2%
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Asked: 2 years ago