AP Biology Midterm Questions
The mechanism of action of many common medications involves interfering with the normal pathways that cells use to respond to hormone signals. Which of the following best describes a drug interaction that directly interferes with a signal transduction pathway? A: A medication enters the target cell and inhibits an enzyme that normally synthesizes a second messenger. B: A medication causes the cell to absorb more of a particular mineral, eventually poisoning the cell. C: A medication enters the target cell's nucleus and acts as a mutagen. D: A medication interrupts the transcription of ribosomal RNA genes.
A: A medication enters the target cell and inhibits an enzyme that normally synthesizes a second messenger.
Damaged tissue releases chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism? A: Activated platelets release chemicals that activate more platelets. B: Activated platelets release chemicals that inhibit blood clot formation. C: Activated platelets constrict the blood vessels, stopping blood flow. D:Activated platelets release signaling molecules that inhibit cell division in damaged tissue.
A: Activated platelets release chemicals that activate more platelets.
If not met, which requirement at the G2 checkpoint could prevent a cell from continuing through the cell cycle? A: Chromosomes are replicated B: Chromosomes are attached to mitotic spindles C: Cell size is sufficiently large D: Sufficient nutrients are available
A: Chromosomes are replicated
Gregor Mendel's pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked on a chromosome? A: Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other. B: Offspring of a given cross show all possible combinations of traits in equal proportions. C: Pea color and pea shape display independent inheritance patterns. D: Recessive phenotypes can skip a generation, showing up only in the parental and F2 generations.
A: Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other.
A prokaryotic cell has which of the following? A: Plasma membrane B: Centrioles C: Endoplasmic reticulum D: Mitochondria E: Lysosomes
A: Plasma membrane
A spherical bacterial cell has a radius of 3μm. The human egg cell has a radius of 100μm. Which statement correctly indicates the cell that is able to more efficiently exchange materials with the external environment and provides a correct explanation? A: The bacterial cell, because it has the largest surface-to-volume ratio. B: The egg cell, because it has the smallest surface-to-volume ratio. C: The egg cell, because it has the largest surface-to-volume ratio. D: The bacterial cell, because it has the smallest surface-to-volume ratio.
A: The bacterial cell, because it has the largest surface-to-volume ratio.
Individuals with an inherited autosomal recessive disorder called primary ciliary dyskinesia (PCD) often have severe respiratory problems due to defective cilia. Males with PCD are often sterile because they produce sperm with defective flagella. Which of the following most likely explains the effect of the recessive allele? A: The cells do not produce functional motor proteins in flagella and cilia. B: The Golgi bodies secrete an enzyme that destroys the proteins in the flagella and cilia. C: The plasma membrane of the alveoli is not permeable to carbon dioxide during respiration because it is too hydrophobic. D: The mitochondria are defective and do not produce sufficient protein to synthesize microtubules in the cilia and flagella.
A: The cells do not produce functional motor proteins in flagella and cilia.
Which of the following is an important difference between light-dependent and light-independent reactions of photosynthesis? A: The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH. B: The light-dependent reactions depend on the presence of both photosystems I and II; the light-independent reactions require only photosystem I. C: The light-dependent reactions utilize CO2 and H2O; the light-independent reactions produce CO2 and H2O. D: The light-dependent reactions occur in the cytoplasm; the light-independent reactions occur in chloroplasts. E: The light-dependent reactions occur only during the day; the light-independent reactions occur only during the night.
A: The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.
Excess intracellular iron is toxic to cells (iron-induced toxicity). Ferritin is an intracellular iron storage protein that binds excess iron. The presence of ferritin can protect cells from iron-induced toxicity. In an experiment to investigate the effects of dietary iron intake on ferritin synthesis, rats were given food containing different amounts of iron. Subsequently, the levels of ferritin protein in the liver were measured. The results are shown in Figure 1. Based on these and other data, researchers have developed the following model demonstrating how ferritin synthesis is regulated by iron. When iron levels are low, a repressor of translation, iron response protein (IRP), binds to an iron response element (IRE), which is a stem-loop structure near the 5¢ end of ferritin mRNA. When iron levels are high, intracellular iron binds to the IRP, and the iron-IRP complex dissociates from the IRE, permitting ribosomes to proceed with the translation of ferritin mRNA. Figure 2 represents the model of the regulation of ferritin mRNA translation by iron. Based on the model of ferritin synthesis presented in Figure 2, which of the following best describes the mechanism whereby iron most likely regulates ferritin production? A: Translation occurs under high intracellular iron concentration when the IRP-iron complex dissociates from ferritin mRNA, permitting ribosomes access to the ferritin coding region. B: Translation occurs under low intracellular iron concentration when the IRP recruits ribosomes to the ferritin mRNA. C: Translation occurs under low intracellular iron concentration when the IRP stabilizes the stem-loop structure in the ferritin mRNA. D: Translation occurs under high intracellular iron concentration when the IRP-iron complex brings the 5¢ end of the mRNA closer to the ferritin coding region.
A: Translation occurs under high intracellular iron concentration when the IRP-iron complex dissociates from ferritin mRNA, permitting ribosomes access to the ferritin coding region.
Researchers studying cell cycle regulation in budding yeast have observed that a mutation in the CDC15 gene causes cell cycle arrest in telophase when the yeast cells are incubated at an elevated temperature. Which of the following statements best predicts the effect of the cell cycle arrest on proliferating yeast cells? A: The yeast cells will replicate their chromosomes but will fail to complete cytokinesis. B: The yeast cells will transition out of G0 but will fail to complete the G1 phase. C: The yeast cells will initiate mitosis but will fail to complete the G2 phase. D: The yeast cells will replicate their organelles but will fail to complete the S phase.
A: The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.
A trisomic cell has A: n3 B: 2n+1 C: n+3 D: 3n
B: 2n+1
During which meiotic phase do chromosomes cross over? A: Anaphase II B: Metaphase I C: Prophase I D: Prophase II
C: Prophase I
All of the following were likely present on the primitive Earth during the evolution of self-replicating molecules EXCEPT A: amino acids and nucleotides B: simple carbohydrates C: nitrogen D: an O2-rich atmosphere E: freestanding liquid water
D: an O2-rich atmosphere
DNA replication occurs... A: in animal cells but not in plant cells B: as the nuclear envelope breaks down in early mitosis C: during mitosis but not during meiosis D: during the S phase of the cell cycle E: only in cells destined to become gametes
D: during the S phase of the cell cycle
The pedigree below shows the inheritance of a dominant allele of a gene in a family over several generations. Circles represent females and squares represent males. Shaded symbols indicate individuals carrying the allele. The pedigree suggests that the gene is on a nuclear chromosome, and not on mitochondrial DNA, because A: mitochondrial DNA is circular, whereas chromosomal DNA is linear B: mitochondrial genes are not heritable C: mitochondrial mutations cannot produce dominant traits D: maternal mitochondrial mutations are inherited by all of a mother's offspring
D: maternal mitochondrial mutations are inherited by all of a mother's offspring
Graphs I-IV depict the effect of pH on the activity of four different hydrolytic enzymes. The most likely explanation for the results shown in Graph I (line increases steadily to the middle, then decreases steadily) is that... A:pH affects the primary structure of the enzyme B: pH affects the temperature of the reaction C: the enzyme has disulfide bonds D: pH affects the shape of the active site of the enzyme E: the enzyme has a quaternary structure
D: pH affects the shape of the active site of the enzyme
_______ is the process in which carbon from CO2 is incorporated into organic molecules. A: Chemiosmosis B: Krebs cycle (citric acid cycle) C: Light-dependent reactions of photosynthesis D: Glycolysis E: Calvin cycle (light-independent reactions of photosynthesis)
E: Calvin cycle (light-independent reactions of photosynthesis)
An experiment is set up to determine the relative volume of O2 consumed by germinating and nongerminating (dry) pea seeds at two different temperatures. The change in volume is detected by using a respirometer over a given period of time. The data are given below. Which of the following conclusions is best supported by the data? A: In the nongerminating pea seeds, oxygen consumption is directly proportional to oxygen concentration. B: Less carbon dioxide is produced by germinating pea seeds at 26ºC than at 10ºC. C: Light is required for pea seed germination. D: Nongerminating pea seeds have a higher rate of respiration than germinating pea seeds do. E: In pea seeds an increase in temperature results in an increase in oxygen consumption.
E: In pea seeds an increase in temperature results in an increase in oxygen consumption.
In dogs, one pair of alleles determines coat color (dark and albino). Another pair of alleles determines hair length (short and long). Thus, each gamete will contain one of the coat-color alleles, C or c and one of the hair-length alleles, B or b. In repeated crosses of a specific dark, short-haired dog with an albino, long-haired dog, all the offspring were dark with short hair, as shown in cross I. However, in subsequent crosses of another dark, short-haired dog with a dark, long-haired dog, the ratios shown in cross II below were obtained. Which of the following correctly describes the relationship of the dark-coat-color allele to the albino condition? A: It is recessive. B: The alleles are linked. C: The alleles are linked. D: It is a polygenic inheritance pattern. E: It is dominant.
E: It is dominant.
A student studied the effects of light intensity on oxygen production in green algae. The algae were suspended in water inside a sealed glass jar, and the jar was placed into a constant-temperature, lightproof box containing a light source. A probe was inserted into the jar to record the concentration of oxygen. The probe was connected to a recording device. The setup is shown below. The student decreased the intensity of the light hourly and recorded the corresponding changes in oxygen concentration. The graph below shows the results from the recording device. The rate of oxygen production equalled the rate of oxygen consumption during which of the following time periods? A: G to H B: H to I C: G to K D: I to J E: J to K
E: J to K
True or False? Genes located on sex chromosomes are mostly related to the development of secondary sexual characteristics.
False
Site of modification and packaging of proteins and lipids prior to export from the cell
Golgi Apparatus
Trisomy 21 is a condition in which a child is born with an extra chromosome in pair 21. Researchers assessed the frequency of children born with trisomy 21 by age of the mothers at birth (maternal age) and primary cause of the error leading to trisomy 21. The findings are presented in Figure 1. Based on the data in Figure 1, which of the following is most likely the primary cause of the pattern of frequency of trisomy 21 births in the selected maternal age-groups? A: At older maternal ages, the incidence of errors in meiosis during egg production increases, which leads to an increase in nondisjunction. B: The incidence of nondisjunction errors in meiosis during sperm production is positively correlated with increasing maternal age. C: Errors in meiosis leading to nondisjunction are more likely to occur during meiosis I than during meiosis II. D: At older maternal ages, there is an increase in the number of errors during mitosis, which leads to an increase in nondisjunction during egg production.
A: At older maternal ages, the incidence of errors in meiosis during egg production increases, which leads to an increase in nondisjunction.
Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown? A: Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP. B: Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol. C: Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of glycogen to glucose. D: Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the endocytotic vesicle.
A: Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP.
Which statement is false? A: In signal transduction, a receptor on the outside of the cell membrane binds to a ligand; the receptor changes shape and transports the ligand into the cell. B: Growth hormones activate transcription factors in the nucleus. C: ATP drives active transport. D: The molecular changes at each step in the signal transduction pathway are short lived.
A: In signal transduction, a receptor on the outside of the cell membrane binds to a ligand; the receptor changes shape and transports the ligand into the cell.
In addition to allowing a gentle energy drop for the electrons, the electron transport chain also creates... A: a hydrogen ion gradient B: oxygen C: ATP D: glucose
A: a hydrogen ion gradient
Excess intracellular iron is toxic to cells (iron-induced toxicity). Ferritin is an intracellular iron storage protein that binds excess iron. The presence of ferritin can protect cells from iron-induced toxicity. In an experiment to investigate the effects of dietary iron intake on ferritin synthesis, rats were given food containing different amounts of iron. Subsequently, the levels of ferritin protein in the liver were measured. The results are shown in Figure 1. Based on these and other data, researchers have developed the following model demonstrating how ferritin synthesis is regulated by iron. When iron levels are low, a repressor of translation, iron response protein (IRP), binds to an iron response element (IRE), which is a stem-loop structure near the 5¢ end of ferritin mRNA. When iron levels are high, intracellular iron binds to the IRP, and the iron-IRP complex dissociates from the IRE, permitting ribosomes to proceed with the translation of ferritin mRNA. Figure 2 represents the model of the regulation of ferritin mRNA translation by iron. Based on the model of ferritin synthesis presented in Figure 2, which of the following describes the role of feedback on the control of intracellular iron levels? A: A decrease in iron levels activates the IRP. The IRP in turn activates iron transport proteins in the cell membrane, thereby returning free iron levels to normal. B: An increase in iron levels activates synthesis of ferritin protein. Ferritin protein in turn binds iron, thereby decreasing both free iron levels and ferritin synthesis. C: An increase in iron levels activates the IRP. The IRP in turn binds iron, thereby decreasing both free iron levels and ferritin synthesis. D: A decrease in iron levels activates synthesis of ferritin protein. Ferritin protein in turn releases bound iron, thereby returning free iron levels to normal.
B: An increase in iron levels activates synthesis of ferritin protein. Ferritin protein in turn binds iron, thereby decreasing both free iron levels and ferritin synthesis.
Glycogen synthetase kinase 3 beta is a protein kinase that has been implicated in many types of cancer. Depending on the cell type, the gene for glycogen synthetase kinase 3 beta (GSK3β) can act either as an oncogene or as a tumor suppressor. Which of the following best predicts how GSK3β mutations can lead to the development of cancer? A: Cells with overactive GSK3β are more likely to repair DNA damage. B: Cells with inactive GSK3β fail to trigger apoptosis. C: Cells with overactive GSK3β have longer cell cycles. D: Cells with inactive GSK3β fail to proceed past the G2/M checkpoint.
B: Cells with inactive GSK3β fail to trigger apoptosis.
Aquaporins are channel proteins that facilitate the transport of water across the cell membrane. One group of researchers hypothesizes that without functional aquaporins, no water will be able to enter the cell. A different group proposes an alternative hypothesis, stating that even with nonfunctional aquaporins, a small amount of water will still cross the cell membrane. An experiment is set up in which plant cells with mutated (nonfunctional) aquaporins and plant cells with normally functioning aquaporins are both placed in distilled water. Which of the following data would support the alternative hypothesis? A: Cells with functional aquaporins exhibit low turgor pressure and are hypertonic. B: Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic. C: Cells with mutated aquaporins exhibit an absence of turgor pressure and are completely plasmolyzed. D: Cells with functional aquaporins exhibit high turgor pressure and are hypotonic.
B: Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.
Cystic fibrosis is a recessively inherited disorder that results from a mutation in the gene encoding CFTR chloride ion channels located on the surface of many epithelial cells. As shown in the figure, the mutation prevents the normal movement of chloride ions from the cytosol of the cell to the extracellular fluid. As a consequence of the mutation, the mucus layer that is normally present on the surface of the cells becomes exceptionally dehydrated and viscous. An answer to which of the following questions would provide the most information about the association between the CFTR mutation and the viscous mucus? A: How does the mutation alter the structure of the CFTR proteins? B: How does the disrupted chloride movement affect the movement of sodium ions and water by the cell? C: What is the change in nucleotide sequence that results in the CFTR mutation? D: Is the mucus also secreted from the cells through the CFTR proteins?
B: How does the disrupted chloride movement affect the movement of sodium ions and water by the cell?
Australian dragon lizards have a ZW sex-determination system. The male genotype is homogametic (ZZ), and the female genotype is heterogametic (ZW). However, all eggs incubated at temperatures above 32°C tend to develop into females. Which of the following best explains how the development of phenotypic female Australian dragon lizards with a ZZ genotype occurs when incubation temperatures are above 32°C? A: At incubation temperatures above 32°C, crossing over transfers genes from the W chromosome to the Z chromosome, producing females. B: Incubation temperatures above 32°C inhibit the genes on the Z chromosome that produce proteins necessary for male development. C: At incubation temperatures above 32°C, Z chromosomes are mutated into W chromosomes. D: Lizard embryos with a ZZ genotype cannot develop at temperatures above 32°C.
B: Incubation temperatures above 32°C inhibit the genes on the Z chromosome that produce proteins necessary for male development.
Scientists have found that DNA methylation suppresses crossing-over in the fungus Ascobolus immersus. Which of the following questions is most appropriately raised by this specific observation? A: Is this species of fungus a diploid organism? B: Is the level of genetic variation in the gametes related to the amount of DNA methylation observed? C: Does DNA methylation result in shorter chromosomes? D: Without crossing-over, will gametes be viable and be able to produce zygotes?
B: Is the level of genetic variation in the gametes related to the amount of DNA methylation observed?
Which of the following can be used to determine the rate of enzyme-catalyzed reactions? A: Rate of disappearance of the product. B: Rate of disappearance of the substrate C: Increase in activation energy D: Change in volume of the solution
B: Rate of disappearance of the substrate
How is the plant cell wall formed after telophase is complete? A: During the G2 phase of the cell cycle, the components of the cell wall are replicated along with other cellular organelles and float freely in the cytoplasm. Once telophase is complete they spontaneously arrange between the two nuclei to form the new cell wall. B: The Golgi apparatus packages up vesicles containing cell wall materials and sends them to the center of the cell. These vesicles collect and begin to form an internal dividing structure with the vesicle membranes becoming the new cell membrane and the vesicle contents fusing assembling as the new cell wall. C: Part of the existing cell wall breaks apart and reforms down the center of the cell, forming the new cell wall. D: Microfilaments form a ring around the cell and contract to pinch the cell in two. The microfilaments become the new cell wall.
B: The Golgi apparatus packages up vesicles containing cell wall materials and sends them to the center of the cell. These vesicles collect and begin to form an internal dividing structure with the vesicle membranes becoming the new cell membrane and the vesicle contents fusing assembling as the new cell wall.
A student crosses a pure-breeding line of red-flowered poinsettias with a pure-breeding line of white-flowered poinsettias. The student observes that all the plants in the F1 generation have pink flowers. The student then crosses the F1 plants with one another and records observations about the plants in the F2 generation. The student will use the F2 data to perform a chi-square goodness-of-fit test for a model of incomplete dominance. The setup for the student's chi-square goodness-of-fit test is presented in Table 1. The critical value for a chi-square test with a significance level of p=0.05 and 2 degrees of freedom is 5.99. Which of the following statements best completes the student's chi-square goodness-of-fit test? A: The calculated chi-square value is 98, and the null hypothesis can be rejected. B: The calculated chi-square value is 1.53, and the null hypothesis cannot be rejected. C: The calculated chi-square value is 1.53, and the null hypothesis can be rejected. D: The calculated chi-square value is 98, and the null hypothesis cannot be rejected.
B: The calculated chi-square value is 1.53, and the null hypothesis cannot be rejected.
Insulin, a hormone secreted by pancreatic cells, stimulates glucose uptake in skeletal muscle cells by mobilizing glucose transporter proteins (GLUT4) to the plasma membrane. As depicted in Figure 1, binding of insulin to the insulin receptor triggers an intracellular signaling cascade in which certain molecules activate other molecules in a relay of the hormone signal to cell targets. One outcome of the signaling cascade is mobilization of GLUT4 from vesicle storage sites in the cytoplasm to sites at the cell surface, where GLUT4 allows glucose to enter the cell. In type 2 diabetes, the cellular response to insulin is disrupted, and individuals with type 2 diabetes cannot properly regulate their blood glucose levels. In an investigation of the insulin signaling pathway, samples of skeletal muscle were isolated from individuals who have type 2 diabetes and from individuals who do not. The results of several experiments that were performed on the muscle samples are shown in Figure 2, Figure 3, and Figure 4. Which of the following is a valid interpretation of the experimental results that explains how individuals with type 2 diabetes differ from individuals without diabetes? A: The relatively low levels of glucose uptake in individuals with type 2 diabetes indicate that no functional GLUT4 protein is produced in the muscle cells of those individuals. B: The relatively low levels of glucose uptake in individuals with type 2 diabetes indicate that mobilization of GLUT4 to the cell surface is reduced in muscle cells of those individuals. C: The absence of activated IRS-1 in individuals with type 2 diabetes indicates that no functional insulin receptor protein is produced in the muscle cells of those individuals. D: The absence of activated insulin receptors in individuals with type 2 diabetes indicates that no insulin is secreted by the pancreatic cells of those individuals.
B: The relatively low levels of glucose uptake in individuals with type 2 diabetes indicate that mobilization of GLUT4 to the cell surface is reduced in muscle cells of those individuals.
A genetic counselor is consulted by a young man who is worried about developing Huntington's disease, an inherited disorder caused by a dominant allele of a single gene. The young man explains that his cousin was recently diagnosed with Huntington's disease, and the news has caused him to consider his own risk of developing the disorder. Which of the following questions will best help the genetic counselor to evaluate the risk of the young man developing Huntington's disease and transmitting it to his children? A: Were you and your cousin born in the same geographical area? B: Were your parents or grandparents ever diagnosed with Huntington's disease? C: Were you in physical contact with a person diagnosed with Huntington's disease? D: Were you ever exposed to substances that are suspected of being mutagens?
B: Were your parents or grandparents ever diagnosed with Huntington's disease?
When a solution has a lower concentration of solutes as the cell cytoplasm, the solution is said to be ______. A: isotonic B: hypotonic C: osmotic D: hypertonic
B: hypotonic
Which of the following is most similar to a membrane receptor protein that recognizes a chemical signal? A: a kinase cascade B: the substrate-specific active site on an enzyme C: a metabolic pathway functioning within a certain organelle D: an enzyme catalyzing at optimum pH
B: the substrate-specific active site on an enzyme
In Mendel's pea-plant experiments, he started with plants that, when allowed to self-pollinate, produced offspring that had the same trait for every character. This type of plant is called ______. A: pure bred B: true breeding C: hybrid D: first filial
B: true breeding
An experiment was performed to determine the mode of inheritance of two mouse genes, one for fur color and one for fur length. It is known that black fur (B) is dominant over white fur (b) and that long fur (L) is dominant over short fur (l). To determine how the genes are inherited, a cross was performed between two true-breeding mice, one with long black fur and one with short white fur. Their progeny, the F1 generation, all had long black fur. Five F1 male-female pairs were then crossed with one another. The F2 generation phenotypes for each cross are shown in Table 1. Which of the following is the mean number per cross of F2 generation offspring that are the result of crossing over? A: 1 B: 2.4 C: 2.2 D: 5.8
C: 2.2
Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. Matthew has a family history of the condition, although he does not express the trait. Jane is an achondroplastic dwarf. Matthew and Jane are planning a family of several children and want to know the chances of producing a child with achondroplastic dwarfism. The probability that Matthew and Jane's first child will be an achondroplastic dwarf is A: 0% B: 100% C: 50% D: 25% E: 75%
C: 50%
Which of the following best describes the formation of the bond shown in Figure 1 ? A: An ionic bond is formed when the negative charge of an OH group is balanced by the positive charge of a hydrogen ion. B: An ionic bond is formed between a carbon atom of one amino acid and the nitrogen atom of the other amino acid. C: A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O D: A covalent bond is formed that replaces the hydrogen bond between the OH group and the H atom.
C: A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O .
The Russian blue is a rare breed of cat that is susceptible to developing cataracts on the eyes. Scientists hypothesize that this condition is inherited as a result of a mutation. Figure 1 shows a pedigree obtained in a study of cats owned by members of the Russian Blue Club in Sweden. Based on the inheritance pattern shown in Figure 1, which of the following best predicts the nature of the original mutation? A: A dominant mutation on the X chromosome B: A recessive mutation on the X chromosome C: A recessive mutation on a somatic chromosome D: A dominant mutation on a somatic chromosome
C: A recessive mutation on a somatic chromosome
Students investigated the effect of light on the carbon cycle in aquatic ecosystems by performing the controlled experiment summarized below. The students placed equal amounts of water (pH 7.0) from a large aquarium in glass beakers. The students transferred aquatic plants from the aquarium to several of the beakers, and then they placed equal numbers of those beakers in the light or dark (Figure 1: groups I and II). Similarly, the students transferred goldfish from the same aquarium to other beakers, and then they placed equal numbers of those beakers in the light or dark (Figure 1: groups III and IV). Finally, the students placed an equal number of beakers containing water only in the light or dark (Figure 1: groups V and VI). After exposing the samples to light or dark for one hour, the students recorded the pH of the water in each beaker. Carbon dioxide dissolved in water will lower the pH of an aqueous solution. In the experiment, the students used changes in pH to monitor changes in the amount of carbon dioxide in the water. For each treatment group, the students calculated the mean pH and standard error, as documented in the table below. Which of the following graphs is the most appropriate representation of the experimental results documented in the table? A: Line graph (Mean pH/Treatment group B: Pie Chart (Relative amount of CO2) C: Bar Graph (Mean pH/Treatment group) D: Scatter plot (Standard error/mean ph)
C: Bar Graph (Mean pH/Treatment Group)
Butterflies of the genus Colias live in the Rocky Mountains, where they experience a wide range of temperatures. Different variants of a particular glycolytic enzyme in the flight muscles are optimally active at different temperatures. Within the same population, some individual butterflies fly most effectively at 29°C , while others fly most effectively at 40°C. Still others can be equally active at both temperatures. Which of the following claims is most consistent with the observed butterfly behavior? A: Butterflies that are active over a wide range of temperatures produce greater amounts of the enzyme. B: Temperature has little effect on the activity of butterflies. C: Butterflies that express two variants of the enzyme are active over a greater range of temperature. D: Butterflies that are active at warmer temperatures produce more offspring.
C: Butterflies that express two variants of the enzyme are active over a greater range of temperature.
Carbon fixation occurs in the stroma. Through carbon fixation, ______ is converted to _______. (fill in the blanks) A: O2; CO2 B: CO2; O2 C: CO2; carbohydrates D: carbon; CO2
C: CO2; carbohydrates
A researcher hypothesizes that RNA molecules were present in the most recent common ancestor of all living organisms. Which of the following scientific questions would best test the hypothesis? A: Is it possible to produce an RNA polymer in a laboratory setting? B: How many different monomers of RNA are found in a eukaryotic cell? C: Do any known organisms function entirely without RNA? D: How many distinct functions can a particular RNA molecule perform in a cell?
C: Do any known organisms function entirely without RNA?
Energy cannot be destroyed, so why can't organisms recycle their energy over and over again? A: High quality energy is degraded to low quality energy during transfers. B: Organisms can recycle their energy over and over. C: Energy is lost (usually as heat) during each transfer. D: Energy cannot change back to a form it has been previously.
C: Energy is lost (usually as heat) during each transfer.
______ is a coenzyme that transfers electrons from the Krebs cycle to the mitochondrial electron-transport chain at a lower energy level than that of electrons entering at the beginning of the chain. A: NAD+ B: Cytochrome C: FADH2 D: Oxygen (O2) E: NADP+
C: FADH2
A model showing two possible arrangements of chromosomes during meiosis is shown in Figure 1. Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1 ? A: Do daughter cells that are not genetically identical to parent cells produce viable zygotes? B: Does DNA methylation prevent independent assortment during metaphase II? C: How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity? D: Does crossing-over generate more genetic diversity than the fusion of gametes does?
C: How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?
Both mitosis and meiosis begin with a parent cell that is diploid. Which of the following best describes how mitosis and meiosis result in daughter cells with different numbers of chromosomes? A: In mitosis, the chromosomes consist of a single chromatid, which is passed to two haploid daughter cells. In meiosis, the chromosomes consist of two chromatids during the first round of division and one chromatid during the second round of division, resulting in two haploid daughter cells. B: In mitosis, synapsis of homologous chromosomes results in four haploid daughter cells after one division. In meiosis, synapsis of homologous chromosomes occurs during the second division and results in four diploid daughter cells. C: Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division. D: Mitosis produces one identical daughter cell after one round of division. Meiosis has two rounds of division and doubles the number of chromosomes in the second round of division, producing four diploid cells.
C: Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.
A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell? A:The nuclear envelope will break down, and the spindle will begin to form. B:Homologous chromosomes (each with two sister chromatids) will move toward opposite poles of the cell. C:Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell. D:The chromatin will decondense, and the daughter cell will enter interphase.
C: Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.
Quorum sensing uses auto-inducers as signaling molecules. Auto-inducers are signaling molecules secreted by bacteria to communicate with other bacteria of the same kind. The secreted auto-inducers can be small, hydrophobic molecules such as acyl-homoserine lactone, (AHL) or larger peptide-based molecules; each type of molecule has a different mode of action. When AHL enters target bacteria, it binds to transcription factors, which then switch gene expression on or off. The peptide auto-inducers stimulate more complicated signaling pathways that include bacterial kinases. The changes in the behavior of bacteria following exposure to auto-inducers can be quite extensive. The pathogenic bacterium Pseudomonas aeruginosa has 616 different genes that respond to auto-inducers. Quorum sensing can be an effective form of cell-to-cell communication for unicellular organisms such as bacteria and yeast. Which statement identifies one weakness of quorum sensing? A: Signal messengers may bind to receptors on cells of a different species, initiating an immune response by the different species. B: Auto-inducers travel slowly and therefore cell responses are slow. C: Quorum sensing is density dependent. Small populations secrete low levels of auto-inducers which will cause a slow response, leaving the population vulnerable to attack. D: Auto-inducers might activate the wrong signaling pathway and cause the wrong genes to be expressed.
C: Quorum sensing is density dependent. Small populations secrete low levels of auto-inducers which will cause a slow response, leaving the population vulnerable to attack.
A researcher claims that different enzymes exhibit maximal function over different pH ranges. To test the claim, the researcher carries out an experiment that includes three different enzymes: pepsin, salivary amylase, and arginase. The results of the experiment are represented in Figure 1. Which of the following actions will provide the most appropriate negative control for the experiment? A: Repeating the experiment with a fourth enzyme B: Repeating the experiment using several different methods for measuring pH C: Repeating the experiment with denatured enzymes D: Repeating the experiment at several different temperatures
C: Repeating the experiment with denatured enzymes
Prokaryotic and eukaryotic cells generally have which of the following features in common? A: Linear chromosomes made of DNA and protein B: A membrane-bound nucleus C: Ribosomes D: Flagella or cilia that contain microtubules E: A cell wall made of cellulose
C: Ribosomes
A student analyzed a viral genome and found that the genome had the following nucleotide composition. • 28% adenine • 20% thymine • 35% cytosine • 17% guanine Which of the following best describes the structure of the viral genome? A: Double-stranded DNA B: Double-stranded RNA C: Single-stranded DNA D: Single-stranded RNA
C: Single-stranded DNA
Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed to induce mitotically dividing S. cerevisiae cells in G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes? A: The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will result in each daughter cell having one-fourth of the original number of chromosomes. B: The first division will move single chromatids to each daughter cell, and the second division will double the number of chromosomes in each daughter cell. C: The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell. D: The first division will result in crossing over between homologous chromosomes, and the second division will reduce the original number of chromosomes by half in the daughter cells.
C: The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.
Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances? A: The proteins bind to molecules secreted by cells located in other parts of the body. B: The proteins leave the cell and travel in the bloodstream to other cells. C: The proteins interact directly with proteins on the surfaces of other cells. D: The proteins receive electrical signals from nerve cells.
C: The proteins interact directly with proteins on the surfaces of other cells.
In an experiment, cells were isolated from an aquatic plant and suspended in pond water, a sucrose sugar solution, or distilled water. All of the cells were then viewed under a microscope. Compared with the cell in the pond water, the cell in the sugar solution appeared shriveled, and the cell in the distilled water appeared inflated. The results of the experiment are represented in Figure 1. Which of the following statements best explains the observations represented in Figure 1 ? A: There was a net movement of sucrose out of the cell suspended in the sugar solution and a net movement of sucrose into the cell suspended in the distilled water. B: There was a net movement of sucrose into the cell suspended in the sugar solution and a net movement of sucrose out of the cell suspended in the distilled water. C: There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water. D: There was a net movement of water into the cell suspended in the sugar solution and a net movement of water out of the cell suspended in the distilled water.
C: There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water.
A hormone A: causes every target cell to respond in the same way. B: only comes in contact with its target cells. C: can stimulate the synthesis and secretion of a different hormone. D: is soluble in water.
C: can stimulate the synthesis and secretion of a different hormone.
Information is usually transmitted from one neuron to the next by means of _____. A: Schwann cells B: membrane potential C: chemical messengers D: oligodendrites
C: chemical messengers
A(n) ______ is a protein that has the ability to lower the activation energy required for a biochemical reaction to take place. A: active site B: substrate C: enzyme D: ribozyme
C: enzyme
The law of segregation (the idea that a gamete cell only gets one allele) is best explained by the fact that A: homologous chromosomes swap genetic material during crossing over. B: sister chromatids are separated during mitosis. C: homologous chromosomes are separated during meiosis I. D: sister chromatids are separated during meiosis II.
C: homologous chromosomes are separated during meiosis I.
A trait that is inherited exclusively through the maternal lineage is likely found A: on the X chromosome. B: on the Y chromosome. C: in mitochondrial DNA. D: on chromosome 1.
C: in mitochondrial DNA.
"The phenotype of a heterozygote is intermediate to the two homozygous phenotypes." This statement most accurately describes ______. A: codominance B: recessive dominance C: incomplete dominance D: complete dominance
C: incomplete dominance
Root hairs, cells of alveoli, cells of villi, microvilli are structures whose function is to A: Improve cell-to-cell communication. B: improve selective permeability of the cell membrane. C: increase the surface area and efficiency of exchange of materials. D: increase mobility of cells.
C: increase the surface area and efficiency of exchange of materials.
tRNA molecules deliver amino acids to ribosomes where the amino acid next... A: forms an ionic bond with another amino acid B: forms hydrogen bonds with esters C: is covalently bonded to a growing polypeptide D: is deaminated and catabolized E: becomes an anticodon
C: is covalently bonded to a growing polypeptide
Paris of matching chromosomes are called ______. A: somatic chromosomes B: sex chromosomes C: sister chromatids D: homologous chromosomes
C: sister chromatids
Pigeons demonstrate ZW sex determination, such that a ZZ genotype produces a male and a ZW genotype produces a female. The gene for feather color is located on the Z chromosome, and the red allele is dominant over the brown allele. Three crosses between brown male pigeons and red female pigeons were performed, and the results are shown below. Which of the following is the mean number of male offspring produced by the three crosses? A: 20 B: 27 C: 11 D: 9
D: 9
Insulin, a hormone secreted by pancreatic cells, stimulates glucose uptake in skeletal muscle cells by mobilizing glucose transporter proteins (GLUT4) to the plasma membrane. As depicted in Figure 1, binding of insulin to the insulin receptor triggers an intracellular signaling cascade in which certain molecules activate other molecules in a relay of the hormone signal to cell targets. One outcome of the signaling cascade is mobilization of GLUT4 from vesicle storage sites in the cytoplasm to sites at the cell surface, where GLUT4 allows glucose to enter the cell. In type 2 diabetes, the cellular response to insulin is disrupted, and individuals with type 2 diabetes cannot properly regulate their blood glucose levels. In an investigation of the insulin signaling pathway, samples of skeletal muscle were isolated from individuals who have type 2 diabetes and from individuals who do not. The results of several experiments that were performed on the muscle samples are shown in Figure 2, Figure 3, and Figure 4. Based on the information presented, which of the following genetic changes in an individual without diabetes is most likely to result in a disrupted cellular response to insulin signaling similar to that of an individual with type 2 diabetes? A: Insertion of a small segment of DNA into the promoter of the Glut4 gene that results in increased synthesis of GLUT4 proteins in muscle cells B: A mutation in the gene encoding IRS-1 that causes the protein to be active in muscle cells even in the absence of insulin signaling C: Duplication of the gene encoding a PI-3 kinase that results in synthesis of a muscle-specific variant of the enzyme in skin cells as well as in muscle cells D: A deletion in the gene encoding the insulin receptor that removes only the cytoplasmic domain of the protein
D: A deletion in the gene encoding the insulin receptor that removes only the cytoplasmic domain of the protein
Muscle contraction depends on ATP hydrolysis. During periods of intense exercise, muscle cells rely on the ATP supplied by three metabolic pathways: glycolysis, mitochondrial respiration, and the phosphagen system. Figure 1 shows the rates at which the three metabolic pathways produce ATP following the start of an intense period of exercise. Figure 1. ATP production by three metabolic pathways following the start of an intense period of exercise Which of the following correctly uses the data to justify the claim that the phosphagen system is an immediate, short-term source of ATP for muscle cells? A: ATP production by the phosphagen system increases gradually and continuously throughout the entire exercise period. B: ATP hydrolysis in muscle cells occurs immediately after the start of the exercise period but stops before the end of the exercise period. C: The ATP produced by the phosphagen system contains more energy per molecule than does the ATP produced by the other pathways. D: ATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period.
D: ATP production by the phosphagen system increases and decreases rapidly following the start of the exercise period.
Figure 1 shows the number of chromosomes observed in an actively dividing human cell at each stage of cell division. Figure 1. Number of chromosomes in a human cell at different stages of cell division Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1 ? A: DNA replication occurs between metaphase and anaphase, doubling the number of chromosomes. Between telophase and cytokinesis, the cell divides in two, with each cell receiving half of the replicated chromosomes. B: New chromosomes formed during prophase are doubled during anaphase and are recombined before cytokinesis. C: At anaphase a cell contains two identical copies of each chromosome, but following telophase, one of the copies is broken down into nucleotides. D: Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.
D: Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.
The illustration shows the active transport of hydrogen ions through a membrane protein. Which of the following best predicts the effect of not having ATP available to supply energy to this process? A: H+ ions will begin to move through the phospholipid portion of the membrane in the original direction. B: H+ ions will continue to move through the protein in the original direction but at a slower rate. C: H+ ions will move in the other direction through the protein. D: H+ ions will stop moving through the protein.
D: H+ ions will stop moving through the protein.
______ is an intermediate electron acceptor for oxidations that occur in both glycolysis and in Krebs cycle reactions. A: FADH2 B: Cytochrome C: NADP+ D: NAD+ E: Oxygen (O2)
D: NAD+
The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6) but different structural formulas, as represented in the figure. Which of the following statements about glucose, galactose, and fructose is most likely true? A. The carbohydrates have different properties because they have different numbers of carbon-carbon bonds. B: The carbohydrates have the same properties because they have the same number of carbon, hydrogen, and oxygen atoms. C: The carbohydrates have the same properties because they each have a single carbon-oxygen double bond. D: The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.
D: The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.
Muscle cells have high ATP demands. Which of the following is a scientific claim about how the structure of the mitochondria in muscle cells should be different than it is in other cells because of the high energy demands of mitochondria? A: The inner membrane of the mitochondria in muscle cells should be more permeable to large enzymes, allowing the same reactions to occur in both compartments of the mitochondria. B: The outer membrane of the mitochondria in muscle cells should be thicker, allowing more rapid diffusion of molecules into the mitochondria. C: The outer membrane of the mitochondria of muscle cells should have more folds, increasing the surface area for faster diffusion of molecules from the cytoplasm. D: The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATP to be synthesized.
D: The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATP to be synthesized.
In animals, the hox genes encode a family of transcription factors that are important for proper development of embryonic segments and are widely conserved in organisms. The figure below shows the embryonic segments in which one such gene, Hoxc6, is expressed in the embryo of a mouse, a chick, and a goose. Embryonic segments are counted from the anterior end. During the formation of vertebrae, the most anterior embryonic segment that expresses Hoxc6 marks the end of the cervical (neck) vertebrae and the beginning of the thoracic (rib) vertebrae. All mammals have seven cervical vertebrae. A: The chick and the goose have the same number of thoracic vertebrae. B: Hoxc6 is expressed in the same embryonic segments in birds and mammals. C: Hoxc6 is expressed in the same vertebra at the anterior end of all bird embryos. D: The most anterior expression of Hoxc6 is the eighth vertebra in mammals.
D: The most anterior expression of Hoxc6 is the eighth vertebra in mammals.
A dialysis-tubing bag is filled with a mixture of 3% starch and 3% glucose and placed in a beaker of distilled water, as shown below. After 3 hours, glucose can be detected in the water outside the dialysis-tubing bag, but starch cannot. From the initial conditions and results described, which of the following is a logical conclusion? A: The initial concentration of glucose in the bag is higher than the initial concentration of starch in the bag. B: The molarity of the solution in the bag and the molarity of the solution in the surrounding beaker are the same. C: A net movement of water into the beaker has occurred. D: The pores of the bag are larger than the glucose molecules but smaller than the starch molecules. E: The bag is not selectively permeable.
D: The pores of the bag are larger than the glucose molecules but smaller than the starch molecules.
Which of the following is a characteristic of mitochondria and chloroplasts that supports the endosymbiotic theory? A: Both can reproduce on their own outside of the cell. B: Both contain ribosomes that are identical to ribosomes of the eukaryotic cytoplasm. C: Both have bacteria-like polysaccharide cell walls. D: Both contain endoplasmic reticulum and Golgi bodies. E: Both contain DNA molecules.
E: Both contain DNA molecules.
Cyclin-dependent Protein Kinases (Cdks) control the cell cycle through phosphorylation. What conclusion can be drawn based on the graph below? A: Increases in protein kinase activity are followed by increases in division of cells, indicating a relationship. B: Low protein kinase activity causes high levels of cell division. C: Cell division initiates spikes in protein kinase activity. D: Cells will always continue to divide regardless of protein kinase activity.
Increases in protein kinase activity are followed by increases in division of cells, indicating a relationship.