In the 1940’s, Avery MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. The transformed cells produced colonies of encapsulated bacteria. Three different procedures and their results are outlined below. Procedure I: Extract made from dead encapsulated cells added to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure II: Extract made from dead encapsulated cells treated with protein-degrading enzymes before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure III: Extract made from dead encapsulated cells treated with DNAse (an enzyme that selectively destroys DNA) before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Only nonencapsulated bacteria grow. A reasonable conclusion to draw from the results of the experiment is that

The first figure is labeled crossing over, and depicts a circle with two sets of chromosomes. The first set of chromosomes overlap in two places. The second set of chromosomes overlap in one place. The second figure is labeled conjugation, and depicts two ovals attached to each other by a thin line. The third figure is titled fertilization, and depicts a circular shape surrounded by numerous sperm shapes, all heading toward the circle. The processes illustrated in the models depicted above all result in which of the following?

In a certain flock of sheep, 4 percent of the population has black wool and 96 percent has white wool. Assume that the population is in Hardy-Weinberg equilibrium. What percentage of the population is homozygous for white wool?

The first two branches are hagfishes and lampreys, from the lampreys branch is a branch for cartilaginous fishes, from the cartilaginous fishes branch is a branch for ray-finned fishes, from the ray-finned fishes branch is a branch for lungfishes, from the lungfishes branch is a branch for amphibians, from the amphibians branch there is another split between monotremes and another split, one side to turtles and the other side splits again to lizards and snakes and to another split of crocodiles and to another split of birds and dinosaurs. From the monotremes there is another branch split of placental mammals and marsupials. To determine the evolutionary history and relationships among organisms, scientists gather evidence from a wide variety of sources including paleontology, embryology, morphology, behavior, and molecular biology. A phylogenetic tree of vertebrates is shown. Which of the following statements is most consistent with the phylogenetic tree shown?

Two species of fish that live in extremely cold environments produce near-identical antifreeze glycoproteins, called AFGPs. Scientists have determined the origins of the AFGP gene in both species. Selected characteristics of the two fish species are provided in Table 1. Table 1. Characteristics of two fish species producing nearly identical antifreeze glycoproteins Fish Species Order Location Evolutionary origin of the AFGP Gene Boreogadus saida Gadiformes Arctic No sequence identity with trypsinogen Dissostichus mawsoni Perciformes Antarctic Pancreatic trypsinogen Based on the information in Table 1, which of the following statements best describes the production of nearly identical AFGPs in these two species of fish?  

Antigens are foreign proteins that invade the systems of organisms. Vaccines function by stimulating an organism’s immune system to develop antibodies against a particular antigen. Developing a vaccine involves producing an antigen that can be introduced into the organism being vaccinated and which will trigger an immune response without causing the disease associated with the antigen. Certain strains of bacteria can be used to produce antigens used in vaccines. Which of the following best explains how bacteria can be genetically engineered to produce a desired antigen?

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 the beakers in the light or the 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. The odd-numbered groups are marked Light, and the even-numbered groups are marked Dark. Each group contains a beaker with the same amount of water. From left to right, the beakers are as follows:1, plant. 2, plant. 3, fish. 4, fish. 5, empty. 6, empty. Figure 1. Treatment groups Mean pH of Treatment Groups After 1 Hour Treatment group (n = 10) I II III IV V VI Mean pH 8.2 6.4 5.9 5.6 7.3 6.8 Standard error of the mean 0.3 0.3 0.2 0.3 0.5 0.4 Which of the following observations provides the best evidence that photosynthesis occurred in treatment group I?

There is strong evidence that two species of cliff-dwelling birds have nested in the same environment and fed in the same water for thousands of years, with each having stable population sizes. Based on this information, which of the following statements is the best conclusion?

A scientist used the amino acid sequence of cytochrome c in different species to consider evolutionary relationships. The data below summarize the number of differences in the amino acid sequences of cytochrome c found in selected species. Differences in the amino acid sequences of cytochrome c found in selected species Species Compared Number of Differences Humans – Chimpanzees 0 Humans – Rhesus monkeys 1 Humans – Horses or donkeys 7 Humans – Cows or pigs or sheep 7 Humans – Rabbits 7 Mammals – Birds and reptiles 10-15 Mammals – Fish 18-20 Animals – Plants 45-48 Interpretation of the data supports which of the following statements?

The lac operon in E. coli consists of genes that code for enzymes necessary for the breakdown of lactose. When lactose is absent, the operon is inactive because a repressor protein binds to a specific site in the lac operon. When lactose is present, lactose molecules bind to the repressor protein, causing the repressor protein to dissociate from the binding site. In the absence of glucose (a preferred energy source for bacteria), the protein CAP binds to a regulatory site near the lac promoter to activate transcription of the lac operon. The following symbols represent the macromolecules involved in regulation of the lac operon. The key indicates that an unshaded circle represents “Repressor,” two shaded hexagons connected by a line represent “Lactose,” an unshaded triangle represents “C A P,” an unshaded oval represents “R N A, polymerase,” and a squiggly line indicates “m R N A.” In the diagrams below, the horizontal line represents the lac operon and the bent arrow represents the transcription start site of the lac operon. Which of the following diagrams best represents the scenario in which lactose is available to the cell and glucose is absent?