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Terms in this set (63)
During an individual organism's lifetime, change in gene expression
is most likely to help the organism respond properly to changes in its environment?
) If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be:
The variable that is likely to undergo the largest change in value as the result of a mutation that introduces a brand-new allele into a population's gene pool at a locus that had formerly been fixed is
The statement about the beak size of finches on the island of Daphne Major during prolonged drought is:
) Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted
Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations
genetic drift most consistently requires a small population as a precondition for its occurrence
In modern terminology, diversity is understood to be a result of genetic variation due to
recombination by crossing over in meiosis is a recognized source of variation for evolution
A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example of:
The higher the proportion of loci that are "fixed" in a population, the lower is that population's
nucleotide variability and average heterozygosity only.
A statement about variation is:
All new alleles are the result of nucleotide variability.
Rank the following one-base point mutations (from most likely to least likely) with respect to their likelihood of affecting the structure of the corresponding polypeptide:
1. deletion mutation within the first exon of the gene
2. substitution mutation at the second position of an exonic codon
3. substitution mutation at the third position of an exonic codon
4. insertion mutation deep within an intron
Most invertebrates have a cluster of ten similar Hox genes, all located on the same chromosome. Most vertebrates have four such clusters of Hox genes, located on four nonhomologous chromosomes. The process that could have potentially contributed to the cluster's presence on more than one chromosome was
A true statement concerning genetic variation is
it arises in response to changes in the environment.
True statements regarding populations are:
1. Mature males and females of a population (species) can interbreed with each other.
2. Populations are sometimes geographically isolated from other populations.
3. Members of a population tend to be genetically more similar to each other than to members of other populations.
Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus:
the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change.
. Calculate the Hardy-Weinberg equilibrium equation q2 + 2pq + q2 = 1.0 or 100%
1. Solve for q2 first because it is usually known because it is the number (or percent in decimal form) of the homozygous recessive (genotype i.e. aa) phenotype. Whereas the phenotype for the heterozygous (2pq) and homozygous (q2) have the same phenotype.
2. The square root of q2 = q
3. 1.0 = p + q
4. Therefore p = 1.0 - q
In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because:
heterozygotes can come about in two ways
) In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because:
heterozygotes have two alleles.
Hardy-Weinberg equilibrium must occur in populations wherein:
no genetic variation exists.
) natural selection is not operating.
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 percentage of the population that is homozygous for this allele?
The recessive allele a = q in the equation. So what is q2 = ?
0.09 or 9%
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 percentage of the population that is heterozygous (2qp) for this allele?
The value of q = 0.2. p = 1.0 - q; so p = 1.0 - 0.2 = 0.8 Therefore 2pq = 2(0.2 x 0.8) =
0.32 or 32.0%
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the frequency of individuals with AA genotype?
0.81 or 81%
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?
The allele frequency cannot be determined from this information
In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?
) can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.
Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing:
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, thereby producing a genetically distinctive virus, which can subsequently cause widespread disease. The production of new types of flu virus in the manner described above is most similar to the phenomenon of:
) Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing:
) If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of both
) founder effect.
Mutations occur at random; natural selection can preserve and distribute beneficial mutations is true of
The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. The outcome of the conflict between bacteria and bacteriophage at any point in time results from:
The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. Over the course of evolutionary time, what should occur?
Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time
Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive):
3 natural selection
4. sexual selection
5. intrasexual selection
Sexual dimorphism is most often a result of:
During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. All three of the following terms are appropriately applied to this situation?
A) sexual selection
B) mate choice
C) intersexual selection
Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then
sexual dimorphism was developing over time in these species.
Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If one excludes the involvement of gender in the situation, then the pattern that is apparent in the fossil record is most similar to one that should be expected from:
A statement that best summarizes evolution as it is viewed today is:
It is the differential survival and reproduction of the most-fit phenotypes
Which of the following is most likely to produce an African butterfly species in the wild whose members have one of two strikingly different color patterns?
Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer, or more, than this have reduced fitness. a term that best describes this situation:
The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet lacks the amino acid phenylalanine.
Diploidy maintains the presence of this harmful allele in a population's gene pool
Heterozygote advantage should be most closely linked to:
) stabilizing selection
In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?
When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., 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:
) frequency-dependent selection.
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. The statement that is supported by these observations is:
Phenotype is often the result of compromise
A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. The actual forelimbs of these mammals do not seem to be optimally arranged because
natural selection is generally limited to modifying structures that were present in previous generations and in previous species.
) 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. The best argument against this misconception:
Advantageous alleles do not arise on demand.
The treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects) is:
using moderate doses of NA and two different PIs at the same time for several months
) Within the body of an HIV-infected individual who is being treated with a single NA, and whose HIV particles are currently vulnerable to this NA, the situations that can increase the virus' relative fitness is
mutations resulting in RTs with increased rates of nucleotide mismatch
HIV has nine genes in its RNA genome. Every HIV particle contains two RNA molecules, and each molecule contains all nine genes. If, for some reason, the two RNA molecules within a single HIV particle do not have identical sequences, then the terms that can be applied due to the existence of the nonidentical regions are:
) nucleotide variability
) average heterozygosity
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:
One of the RNA molecules has experienced gene duplication as the result of translocation.
) In a hypothetical population's gene pool, an autosomal gene, which had previously been fixed, undergoes a mutation that introduces a new allele, one inherited according to incomplete dominance. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations?
The proportions of both types of homozygote should decrease.
The most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time is:
The two phenotypes are about equally adaptive under laboratory conditions.
What is the estimated frequency of allele A in the gene pool?
q = 50% or 0.5 therefore A (p) = 1 -q
Or ) 0.50
What proportion of the population is probably heterozygous (Aa) for this trait?
In the United States, the parasite that causes malaria is not present, but African-Americans whose ancestors were from equatorial Africa are present. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa?
directional selection; stabilizing selection
With respect to the sickle-cell allele, what should be true of the β hemoglobin locus in U.S. populations of African-Americans whose ancestors were from equatorial Africa?
) The average heterozygosity at this locus should be decreasing over time.
) Diploidy is helping to preserve the sickle-cell allele at this locus.
Considering the overall human population of the U.S. mainland at the time when the slave trade brought large numbers of people from equatorial Africa, what was primarily acting to change the frequency of the sickle-cell allele in the overall U.S. population?
The sickle-cell allele is pleiotropic (i.e., it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles such as this can help explain why
adaptations are often compromises.
) Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others
No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is:
the reshuffling of alleles in sexual reproduction.
If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?
gene variability = 0%; number of alleles = 1
There are 40 individuals in population 1, all with genotype A1A1, and there are 25 individuals in population 2, all with genotype A2A2. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is most likely an example of:
) A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2
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