In a small group of people living in a remote area, there is a high incidence of “blue skin”, a condition that results from a variation in the structure of hemoglobin. All of the “blue-skinned” residents can trace their ancestry to one couple, who were among the original settlers of this region. The unusually high frequency of “blue skin” in the area is an example of

From left to right, the model begins with two virus structures. The structure on top is an Avian Influenza Virus, with the R N A Molecules and Glycoprotein X labeled. The bottom structure is a Human Influenza Virus, with the R N A Molecules and Glycoprotein Y labeled. A right-facing arrow points from each virus to a Pig Respiratory Tract Cell with D N A Molecules labeled. A right-facing arrow points from the Pig Respiratory Tract Cell to a New Strain of Human Influenza Virus, with the R N A Molecules and Glycoprotein Z labeled. The cells lining the respiratory tract of pigs have receptors for both avian and human influenza viruses. Based on the model above, which of the following best describes the origin of the new strain of human influenza virus?

Ellis-van Creveld syndrome is a recessive genetic disorder that includes the characteristics of short stature and extra fingers or toes. In the general population, this syndrome occurs in approximately 1 in 150,000 live births. In a particular isolated population, however, the incidence of this syndrome among live births is 1 in 500. Assume that both the isolated population and the general population are in Hardy-Weinberg equilibrium with respect to this syndrome. Which of the following best describes the difference between the frequency of the allele that causes the syndrome in the general population and the frequency of the allele in the isolated population?

A model of a process involving nucleic acids is shown in Figure 1. The figure presents a diagram of a replication fork that is growing to the right. Strands that are complementary to the separated template strands on the left side of the fork have already been synthesized. The template strands on the right side remain single stranded. The left end of the upper template strand is labeled 5 prime, and the right end is labeled 3 prime. Two sequential arrows that point from right to left represent the process of strand synthesis with nucleotides that are complementary to the upper template strand. The left end of each arrow is labeled 3 prime, and the right end of each is labeled 5 prime. The left end of the lower template strand is labeled 3 prime, and the right end is labeled 5 prime. A single long arrow that points from left to right represents the process of strand synthesis with nucleotides that are complementary to the lower template strand. The left end of the arrow is labeled 5 prime, and the right end is labeled 3 prime. Figure 1. Model of a process involving nucleic acids Which of the following best explains what process is represented in Figure 1?

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?