Author: Anonymous

The TAS2R38 gene encodes a receptor protein that influences the ability to taste bitterness. The gene has two alleles: a dominant, wild-type allele that enables an individual (taster) to taste bitterness and a recessive, mutant allele that interferes with the ability of an individual (nontaster) to taste bitterness. Three single nucleotide mutations in the coding region of the TAS2R38 gene are associated with the nontaster allele. The nucleotides present at the three positions are shown in the table below. Nucleotide Variation in the TAS2R38 Gene Position in the Nucleotide Sequence 145 785 886 Human nontaster G T A Human taster C C G Bonobo C C G Chimpanzee C C G Gorilla C C G A cladogram representing the evolutionary relatedness of selected primates is shown below. From left to right, the branches are as follows: Orangutan, Gorilla, and Chimpanzee. Past the branches, the main line is labeled Human. Another branch, labeled Bonobo, is connected to the Chimpanzee branch. Toxic substances often have a bitter taste that causes animals who try to eat such substances to spit them out rather than swallow them. Additional data suggest that gorilla populations have a very low frequency of nontasters. Which of the following conclusions is supported by the data?

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. Which of the following best justifies the use of the study area to investigate how one species influences the behavior of another?

The following questions refer to the following DNA strand and table of codons. Each triplet of DNA bases is numbered from one to seven. Triplet 1 is T, A, G, triplet 2 is T, T, C, triplet 3 is A, A, A, triplet 4 is C, C, G, triplet 5 is C, G, T, triplet 6 is A, A, C, triplet 7 is A, T, T. The figure shows the universal codon table with 4 main data rows and 4 main data columns. The left side of the table is labeled First Base in Codon, and labels the main rows, from top to bottom, U, C, A, G. The top side of the table is labeled Second Base in Codon, and labels the main columns, from left to right, U, C, A, G. The right side of the table is labeled, Third Base in Codon, and labels each of the main rows U C A G.The data in the table reads as follows: First Base U and Second Base U with Third Base U, results in U U U phenylalanine; with Third Base C results in U U C phenylalanine; with Third Base A, results in U U A leucine, and with Third Base G, results in U U G leucine. First Base C and Second Base U with Third Base U, results in C U U leucine; with Third Base C, results in C U C leucine; with: Third Base A, results in C U A leucine, and with Third Base G, results in C U A leucine. First Base A and Second Base U with Third Base U, results in A U U isoleucine; with Third Base C, results in A U C isoleucine; with Third Base A, results in A U A isoleucine; and with Third Base G, results in A U G methionine or start. First Base G and Second Base U with Third Base U, results in G U U valine; with Third Base C, results in G U C valine; with Third Base A, results in G U A valine, with Third Base G, results in G U G valine. First Base U and Second Base C with Third Base U, results in U C U serine; with Third Base C, results in U C C serine; with Third Base A, results in U C A serine; and with Third Base G, results in U C G serine. First Base C and Second Base C with Third Base U, results in C C U proline; with Third Base C, results in C C C proline; with Third Base A, results in C C A proline; and with Third Base G, results in C C G proline. First Base A and Second Base C with Third Base U, results in A C U threonine; with Third Base C, results in A C C threonine; with Third Base A, results in A C A threonine; and with Third Base G, results in A C G threonine. First Base G and Second Base C with Third Base U, results in G C U alanine; with Third Base C, results in G C C alanine; with Third Base A, results in G C A alanine; and with Third Base G, results in G C G alanine. First Base U and Second Base A with Third Base U, results in U A U tyrosine; with Third Base C, results in U A C tyrosine; with Third Base A, results in U A A stop; and with Third Base G, results in U A G stop. First Base C and Second Base A with Third Base U, results in C A U histidine; with Third Base C, results in C A C histidine; with Third Base A, results in C A A glutamine; and with Third Base G, results in C A G glutamine. First Base A and Second Base A with Third Base U, results in A A U asparagine; with Third Base C, results in A A C asparagine; with Third Base A, results in A A A lysine; and with Third Base G, results in A A G lysine. First Base G and Second Base A with Third Base U, results in G A U aspartate; with Third Base C, results in G A C aspartate; with Third Base A, results in G A A glutamate; and with Third Base G, results in GAG glutamate. First Base U and Second Base G with Third Base U, results in U G U cysteine; with Third Base C, results in U G C cysteine; with Third Base A, results in U G A stop; and with Third Base G, results in U G G tryptophan. First Base C and Second Base G with Third Base U, results in C G U arginine; with Third Base C, results in C G C arginine; with Third Base A, results in C G A arginine; and with Third Base G, results in C G G arginine. First Base A and Second Base G with Third Base U, results in A G U serine; with Third Base C, results in A G C serine; with Third Base A, results in A G A arginine; and with Third Base G, results in A G G arginine. First Base G and Second Base G with Third Base U, results in G G U glycine; with Third Base C, results in G G C glycine; with Third Base A, results in G G A glycine; and with Third Base G, results in G G G glycine. Which of the following modifications of the DNA would produce the greatest change in the primary structure of the polypeptide chain?

Analysis of DNA sequences from two individuals of the same species results in a greater estimate of genetic variability than does analysis of amino acid sequences from the same individuals because

Some strains of the bacterium Streptococcus pyogenes secrete poisonous substances called exotoxins. The genes encoding the exotoxins are thought to have originated in bacteriophages, which are viruses that infect bacteria. Which of the following is the most likely mechanism by which the S. pyogenes acquired the ability to produce the exotoxins?

Potatoes as a food crop originated in South America. There are over 4,000 variations of potato grown there. Potatoes were brought to Europe by Spanish colonists in the late 1500s. One variety became the chief crop grown in much of Ireland by the early 1800s. Table 1 summarizes the spread of potatoes as a food crop. Table 1. Spread of potatoes as food crop from origin in South America Time Period Location Number of Potato Varieties (approximate) Pre-1567 South America 4,000 1567-1800 Europe 12 1840-1850 Ireland 1 The Irish Lumper variety of potato was introduced into Ireland in the early 1800s. The Lumper soon became the only variety of potato grown in much of Ireland. The potato blight destroyed most of the Lumper crop between 1845 and 1852 resulting in the death of about 1 million Irish from starvation. A researcher suggests that the Irish monoculture (growing a single crop) of the Lumper potato did not significantly change the overall resistance of the potato crop in Ireland to diseases. Which of the following observations best refutes this null hypothesis?

There are two small black, shaded circles on the plate. The one on the left is labeled A and is surrounded by an unshaded circle on the agar. There is also another small black dot next to the circle. The other circle is labeled P and has no other visible change on the agar. A sterile agar plate, I, is streaked with a pure culture of bacteria by means of aseptic techniques. Paper discs treated with the antibiotics Aureomycin (A) and penicillin (P) are placed at opposite sides of the plate, as shown in the diagram above. The plate is examined after a 24-hour incubation period, and a clear ring is discovered around disc A, but not around disc P. Within the clear ring around disc A, a single bacterial colony with physical characteristics like those of the pure culture is observed. A second sterile agar plate, II, is then streaked with this single colony and also incubated with antibiotics. The single colony found within the clear ring in plate I is most likely made up of the descendants of a bacterial cell that

The horizontal axis is labeled Time and the vertical axis is labeled Population Size, N. An S shaped curve on the graph begins at the origin, moves briefly to the right along the horizontal axis, then curves up and to the right, continues steeply upward in almost a straight line, and then begins to level off near the top of the graph by curving to the right and running parallel to the horizontal axis. Four sections of the S curve are labeled. Starting at the bottom of the S curve, the first upward curve is labeled IV. The center of the steep upward section of the curve is labeled III, the top curve, where it begins to move horizontally to the right, is labeled II, and the end of the S curve, in the upper right region of the graph, is labeled I. One model of a sustainable fisheries practice is for individual fish to be removed from a natural population at a rate equal to the highest possible growth rate of an ideal population. The graph above represents a population of bluefin tuna living along the Atlantic coast. At which labeled point in the graph is the population growth rate the highest?

Living cells typically have biosynthetic pathways to synthesize at least some of the amino acids used in making proteins. Some strains of E. coli, a prokaryote, can synthesize the amino acid tryptophan, while other E. coli strains cannot. Similarly, some strains of the yeast S. cerevisiae, a eukaryote, can synthesize tryptophan, while other S. cerevisiae strains cannot. Which of the following describes the most likely source of genetic variation found in the tryptophan synthesis pathways of both species?

Histone methyltransferases are a class of enzymes that methylate certain amino acid sequences in histone proteins. A research team found that transcription of gene R decreases when histone methyltransferase activity is inhibited. Which scientific claim is most consistent with these findings?