The diagram below illustrates the results of electrophoresis of DNA sequences obtained from a family of two adults and three children, and amplified using PCR. The bands represent short repeating sequences of variable length. Results for another female (X) are included for comparison. Beginning with the origin there are six lengths of DNA fragments that have separated on the gel. For each fragment the individual that has a band at that basepair length on their gel will be listed. The largest fragment, fragment one: father, child one. Fragment two: child three. Fragment three: mother, child one, child two, X. Fragment four: X. Fragment five: father, child two, child three. Fragment six: mother. Which of the following is the best explanation for the fragment pattern for individual X ?

A new mutation that arose in one copy of gene X in a somatic cell resulted in the formation of a tumor. Which of the following pieces of evidence best describes how the new mutation directly caused the tumor?

Both liver cells and lens cells have the genes for making the proteins albumin and crystalline. However, only liver cells express the blood protein albumin and only lens cells express crystalline, the main protein in the lens of the eye. Both of these genes have enhancer sequences associated with them. The claim that gene regulation results in differential gene expression and influences cellular products (albumin or crystalline) is best supported by evidence in which of the following statements?

To investigate the influence of predation risk on ray behavior, a student observed and counted the large marine animals swimming in a shallow, nearshore section of a coral reef ecosystem. The time of each observation was recorded relative to the time of high tide. The student noted that at low tide, when the water level is low, many of the large animals are forced out of the study area and into the deeper waters of the outer reef. During high tides, when the water level is high, the large animals are able to reenter the study area. Over a three-day period, the student observed a total of 604 individual rays belonging to three species: cowtail rays, giant shovelnose rays, and black stingrays. For each ray that was sighted, its body length was estimated and its status as either alone (ungrouped) or found with other rays (grouped) was noted. Occasionally, rays were observed sifting through the sandy substrate of the study area to capture food items such as molluscs and crustaceans. In one instance, an injured ray with bite marks that were likely sustained in a shark attack was sighted. In addition to the rays, the student observed lemon sharks (n = 46) and blacktip reef sharks (n = 39). The results of the study are presented in the figures below. The horizontal axis is labeled “Mean Body Length, in meters,” and the numbers 0 through 1.5, in increments of 0.5, are indicated. The vertical axis gives the three categories of the graph, each of which contains two subcategories. The three categories are Cowtail Rays, Giant Shovelnose Rays, and Black Stingrays. The subcategories are Ungrouped and Grouped. The data are presented as follows. Note that all values are approximate. Cowtail Rays: Ungrouped have a mean body length of 1.5 meters, and the error bar spans plus or minus 0.03. Grouped have a mean body length of 1.35 meters, and the error spans plus or minus 0.05. Giant Shovelnose Rays: Ungrouped have a mean body length of 1.6 meters, and the error bar spans plus or minus 0.04. Grouped have a mean body length of 1.35 meters, and the error spans plus or minus 0.08. Black Stingrays: Ungrouped have a mean body length of 1.4 meters, and the error bar spans plus or minus 0.02. Grouped have a mean body length of 1.3 meters, and the error spans plus or minus 0.05. Figure 1. Comparison of mean body lengths of the grouped and ungrouped rays that were observed in a nearshore section of a coral reef ecosystem. Error bars represent 2SEx̄ The graph shows the mean number of rays per group in the study area relative to stages of the tide cycle. The horizontal axis is labeled “Time Relative to High Tide, in hours,” and the numbers negative 3 through positive 1, in increments of 1, are indicated. The vertical axis is labeled “Mean Group Size,” and the numbers 0 through 6, in increments of 1, are indicated. The line is composed of five points connected by line segments, and error bars are shown for each point. The five points are listed as follows. Note that all values are approximate. Point 1. Time relative to High Tide, negative 3 hours. Mean Group Size, 0.9 plus or minus 0 point 4. Point 2. Time relative to High Tide, negative 2 hours. Mean Group Size, 2 point 5 plus or minus 0 point 2. Point 3. Time relative to High Tide, negative 1 hours. Mean Group Size, 4 point 4 plus or minus 0 point 9. Point 4. Time relative to High Tide, 0 hours. Mean Group Size, 4 point 6 plus or minus 0 point 1. Point 5. Time relative to High Tide, positive 1 hours. Mean Group Size, 3 point 6 plus or minus 0 point 3. Figure 2. Mean numbers of rays per group in the study area at different stages of the tide cycle. High tide occurs at T = 0 hours. The graph shows the relative proportions of rays in groups at different stages of the tide cycle. A key indicates that three different lines represent giant shovelnose rays or black stingrays or cowtail rays. The horizontal axis is labeled “Time relative to High Tide, in hours,” and the numbers negative 3 through positive 1, in increments of 1, are indicated. The vertical axis is labeled “Relative Proportion of Rays Found in Groups” and has an arrowhead at the top end. The line for each type of ray is composed of five points connected by line segments, and error bars are shown for most points. The data for each time point are as follows. Point 1. Time relative to High Tide, negative 3 hours. The proportion of each type of ray is similar, and there are very few of each type. Point 2. Time relative to High Tide, negative 2 hours. The number of cowtail rays increased slightly, and there are about twice as many giant shovelnose rays and six times as many black stingrays as cowtail rays. Error bars are shown for only the cowtail rays and giant shovelnose rays. The upper end of the cowtail rays error bar touches the lower end of the giant shovelnose rays error bar. Point 3. Time relative to High Tide, negative 1 hours. The number of cowtail rays is double the number at negative two hours, and there are about three times as many giant shovelnose rays and five times as many black stingrays as cowtail rays. Error bars are shown for each point. The error bar range for the cowtail rays is very narrow; the error bars for the black stingrays and giant shovelnose rays are broad, but do not overlap. Point 4. Time relative to High Tide, 0 hours. The number of cowtail rays is about three quarters the number at negative one hours, and there are about twelve times as many giant shovelnose rays and nine times as many black stingrays as cowtail rays. The error bar range for the cowtail rays is very narrow; the error bars for the black stingrays and giant shovelnose rays are broad, and the upper end of the black stingrays error bar touches the lower end of the giant shovelnose rays error bar. Point 5. Time relative to High Tide, positive 1 hours. The number of cowtail rays is just slightly greater than the number at 0 hours, and there are about seven times as many giant shovelnose rays and five times as many black stingrays as cowtail rays. The error bar range for the cowtail rays is very narrow; the error bars for the black stingrays and giant shovelnose rays are broad, and the upper end of the black stingrays error bar touches the lower end of the giant shovelnose rays error bar. Figure 3. Relative proportions of rays in groups at different stages of the tide cycle for each of the three different populations. High tide occurs at T = 0 hours. The graph shows the mean numbers of lemon sharks and blacktip reef sharks at different stages of the tide cycle. A key indicates that one line represents lemon sharks, and the other line represents blacktip reef sharks. The horizontal axis is labeled “Time Relative to High Tide, in hours,” and the numbers negative 3 through positive 1, in increments of 1, are indicated. The vertical axis is labeled “Mean Number of Sharks,” and the numbers 0 through 10, in increments of 1, are indicated. The two curves are composed of five points connected by line segments. No error bars are shown. The five points of each line are listed as follows. Note that all values are approximate. The following five points are indicated on the line representing lemon sharks. Point 1. Time relative to High Tide, negative 3 hours. Mean Number of Sharks, 4.2. Point 2. Time relative to High Tide, negative 2 hours. Mean Number of Sharks, 9. Point 3. Time relative to High Tide, negative 1 hours. Mean Number of Sharks, 1.5. Point 4. Time relative to High Tide, 0 hours. Mean Number of Sharks, 0. Point 5. Time relative to High Tide, positive 1 hours. Mean Number of Sharks, 1. The following five points are indicated on the line representing blacktip reef sharks. Point 1. Time relative to High Tide, negative 3 hours, Mean Number of Sharks, 0.3. Point 2. Time relative to High Tide, negative 2 hours, Mean Number of Sharks, 0.3. Point 3. Time relative to High Tide, negative 1 hour, Mean Number of Sharks, 4. Point 4. Time relative to High Tide, 0 hours, Mean Number of Sharks, 7. Point 5. Time relative to High Tide, positive 1 hour, Mean Number of Sharks, 9. Figure 4. Mean numbers of lemon sharks and blacktip reef sharks in the study area at different stages of the tide cycle. High tide occurs at T = 0 hours. Based on the results of the study, which of the following is the most likely connection between behavior and evolutionary fitness in a nearshore coral reef environment?

Rr. Robert Hazen has worked to develop a hypothesis that explains the origin of life on Earth. His work has focused on hydrothermal vents, which are cracks in the ocean floor. Water heated by molten rock beneath the crust escapes from these vents at very high temperatures, producing hot, high‑pressure environments at the vents on the ocean floor. In order to provide evidence that these vents may be areas where life originated, which of the following states a null hypothesis Hazen might have used to begin his research?

Figure 1 represents part of a process essential to gene expression. The two strands of the helix are paired at each end but are separated in the central portion. Bases of the nucleotides are indicated for the entire length of each strand. The left end of the upper strand is labeled 5 prime, and the right end is labeled 3 prime. The left end of the lower strand is labeled 3 prime, and the right end is labeled 5 prime. The lower strand is also labeled Strand X. An additional single strand of nucleotides that is complementary to the lower DNA strand is also present on the left and central portions of the figure. The sequence of the strand, from the left 5 prime end to the right 3 prime end, is as follows: A U G C C G C A A U C U G U U C A C G C A C U C A U G U G. Above the strand an arrow labeled Direction of Synthesis points along the strand from left to right. Figure 1. Model of process involved in gene expression. Which of the following best explains what strand X represents?

In an experiment on the effects of deforestation of a portion of a northern temperate deciduous forest, all the trees were removed from a small mountainside watershed area and herbicides were applied for three years to prevent regrowth. Measurements of the concentration of calcium (an important nutrient) in runoff water were taken both before and after the deforestation. Monthly measurements also were made in a similar watershed in another part of the same forest that had been left undisturbed. The findings are displayed in the graph below. The figure shows a graph in quadrant one titled Monthly Measurements Of Calcium Concentration In Runoff Water. The horizontal axis has every month from June, 1965 to May, 1968, with a tick mark at each month. The vertical axis is labeled calcium ion concentration in runoff water in milligrams per liter, from zero to eleven in increments of one. The time of deforestation is marked at December 1965. There is a dashed line labeled losses from undisturbed watershed that remains at one milligram per liter with only slight fluctuations from June 1965 until the end of the graph in May 1968. There is a solid line labeled losses from disturbed watershed. The calcium ion concentration in runoff water for losses from disturbed watershed is approximately one milligram per liter from June 1965 until May 1966. There is a sharp increase from May to July where the ion concentration reaches seven milligrams per liter, then drops to five in August, and continues rising with fluctuations until October 1966 when it reaches a concentration of nine milligrams per liter. There is a decrease over time, with fluctuations, to six milligrams per liter by May 1967, when the concentration increases rapidly to above eleven, peaking in September 1967, then decreasing steadily with small fluctuations to approximately four milligrams per liter in May 1968. Which of the following is best supported by the data?

Erwin Chargaff investigated the nucleotide composition of DNA. He analyzed DNA from various organisms and measured the relative amounts of adenine (A), guanine (G), cytosine (C), and thymine (T) present in the DNA of each organism. Table 1 contains a selected data set of his results. Table 1. Nucleotide composition of selected organismsample DNA from Organism %A %G %C %T %(G+C) %(A+T) Octopus 33.2 17.6 17.6 31.6 35.2 64.8 Chicken 28.0 22.0 21.6 28.4 43.7 56.4 Rat 28.6 21.4 20.5 28.4 42.9 56.0 Grasshopper 29.3 20.5 20.7 29.3 41.2 58.6 Wheat 27.3 22.7 22.8 27.1 45.5 54.4 Which of the following statements best explains the data set?

Phytoplankton (black line) are important because they occupy the bottom of the food web absorbing CO2, functioning as a carbon sink. A scientist suggests that an El Niño event in early 1998 caused a significant decrease in the abundance of phytoplankton that year in the equatorial Pacific Ocean. The horizontal axis is labeled Year, and the years 1990 through 2000, in increments of 2, are indicated. The vertical axis is labeled, Relative Plankton Density. A key indicates that one line represents zooplankton and the other line represents phytoplankton. The data represented in the graph are as follows. Note, all data are approximate. Data for zooplankton. The line begins approximately one third of the way up the vertical axis above the origin and trends slightly upwards and to the right, fluctuating up and down across the length of the horizontal axis with upward spikes approximately every two years, and a significant downward spike at the year 1998 that falls to just above the horizontal axis. Data for phytoplankton. The line begins just below the midpoint on the vertical axis, above the origin, and trends slightly upwards and to the right, fluctuating up and down across the length of the horizontal axis, staying above the line for zooplankton and with a significant downward spike at the year 1998 that falls one third of the way up the vertical axis, comes back up by 1999, and remains fairly constant after that. Figure 1. Relative abundance of plankton over time in the eastern equatorial Pacific Ocean Which of the following observations would best support this alternative hypothesis?

There is a horizontal rectangle that is labeled D N A. The rectangle is divided into 9 boxes. From left to right, the first box is labeled P sub r, the second box is labeled trp R, the third box is labeled promoter, the fourth box is labeled Operator, the fifth box is labeled trp E, the sixth box is labeled trp D, the seventh box is labeled trp C, the eighth box is labeled trp B, and the ninth box is labeled trp A. Above the rectangle on the left is a large oval shape labeled R N A Polymerase. An arrow extends from the oval shape to the right and points to an X that is positioned above the boxes labeled Promoter and Operator. An irregular shape that looks like half of a circle and which is labeled R is positioned on top of the boxes labeled Promoter and Operator. A smaller oval shape labeled T is positioned partly on top of the shape labeled R. Underneath the rectangle, an arrow points downward from the box labeled trp R to a small, horizontal rectangle labeled trp R m R N A. On the left side of the rectangle is a 5 prime and a dash. On the right side of the rectangle is a dash and a 3 prime. An arrow points from the rectangle to a large oval shape labeled R. The large oval shape has a smaller oval shape cut out of it. To the left of the large oval shape are the words Inactive Repressor. A horizontal arrow points from the large oval shape to an irregular shape that looks like half of a circle and which is labeled R. A smaller oval shape labeled T is positioned partly on top of the shape labeled R. To the left of the irregular shape are the words Active Repressor. Above and to the left of the irregular shape is a small oval shape labeled T. A curved arrow extends from the shape labeled T down and to the right, eventually merging with the horizontal arrow that extends from the large oval shape on the left to the irregular shape on the right. A curved arrow extends from the irregular shape up and counterclockwise to point to the same shape that is positioned on top of the boxes labeled Promoter and Operator. There is a key below the figure that reads R equals Repressor molecule, T equals Tryptophan molecule, P sub R equals Promoter for the trp R gene, trp R equals Repressor gene, and Operator equals Binding site for repressor molecule. The Trp operon is a coordinately regulated group of genes (trpA–trpE) that are required for tryptophan biosynthesis in E. coli. Based on the figure above, which of the following correctly describes the regulation of the Trp operon?