Bio Study Questions

A scientist adds a chemical to a culture of dividing cells in order to disrupt DNA replication. The replicated DNA produced by the cells is double-stranded, but sections of it lack covalent bonds between adjacent nucleotides. Which of the following claims is best supported by the data?

The chemical inhibits DNA ligase

A researcher is investigating the effects of a chemical that makes thylakoids membranes permeable to hydrogen ions (H+). Which of the following is the most likely direct effect of adding the chemical to plant cells?

The chloroplasts will generate less ATP

Beta thalassemia is a disorder caused by mutations in the HBB gene. Examination of the HBB protein in an individual with beta thalassemia shows that the protein is missing many amino acids at its carboxyl terminus. Which of the following is the most likely explanation for how a mutation in the DNA could result in the loss of the carboxyl terminus of the HBB protein?

The mutation changes a codon in the coding region of the HBB transcript to a stop codon such that translation terminates earlier than it should

A researcher observes that when two heterozygous plants with red flowers are crossed, they resulting offspring include plants with red, white, or pink flowers. The researcher proposes the null hypothesis that flower color is the result of independent assortment and incomplete dominance. The researcher calculates a chi-square value of 7.3. Assuming two degrees of freedom, which of the following is the correct interpretation of the chi-square analysis, using a p-value of 0.05?

The null hypothesis should be rejected because the critical value is less than the calculated value

Goats and sheep belong to the same family but different genera. While they often live together in the same pastures, the hybrid offspring that are occasionally produced between the two species rarely survive. When such a hybrid does survive, it is usually sterile. Which of the following best explains the mechanism that maintains reproductive isolation between goats and sheep?

The two species have a different number of chromosomes, resulting in a post zygotic barrier

In the spring and summer, the fur of an arctic fox contains a pigment called melanin that gives the fox's fur a dark color. In the fall and winter, the fur of the arctic fox turns white. Which of the following most likely explains how the changing seasons result in changing fur color in an arctic fox?

Environmental factors cause changes in gene expression, resulting in seasonal variations in pigment production

(#1)The brown anole (Anolis sagrel) is a species of lizard native to Cuba that has been introduced into the southeastern United States. The range of brown anoles in the United States has been expanding, and they are now competing with native green anoles (Anolis carolinensis). Some of the characteristics of the green and brown anoles are shown in Table 1. Based on the data in Table 1, which of the following best explains the observed differences in cold tolerance between brown anoles (A. sagrel) and green anoles (A. carolinensis) in the United States?

Green anoles with greater tolerance for cold had greater reproductive success in areas with colder temperatures

Researchers analyzed the amino acid sequences of the protein cytochrome c in various groups of organisms and determined the number of amino substitutions that have occurred in the different groups of organisms. They plotted the data with respect to the time since divergence of the members of paired groups from a common ancestor (Figure 1). Based on the data, which of the following organisms are more distantly related?

Insects and vertebrates

Researchers studying new viruses analyzed the genetic material found in four different virus samples to determine the percent nitrogen base composition of each virus. The data is shown in the table Which of the following samples most likely contains a double-stranded RNA virus?

Sample 1

Which of the following is the strongest evidence supporting the endosymbiont hypothesis?

Mitochondria have their own DNA and divide independently of the cell

(1)A student is investigating photosynthesis in plants. The student planted grass seeds in a tray with three sections and grew the grass under artificial lights for 14 days (Figure 1). After 14 days, the student collected all of the grass from section I and recorded its mass (Table 1). The student then placed a clear cover over section II and placed an aluminum foil cover over section III (Figure 2). The student then placed the tray back under the artificial lights for even additional days. On day 21, the student collected and measured the mass of the grass from sections II and III (Table 1). Based on the data, which of the following is the best approximation of the rate of growth per week in section II from day 14 to day 21?

4.5 g/week

Poaching is the illegal hunting or capturing of wild animals. Both male and female African elephants have tusks that are a significant source of ivory used for ornaments and jewelry. Assuming that the size of the tusks is heritable, which of the following is the most likely long-term effect of poachers targeting African elephants with large tusks?

A decrease in average tusk size because the elephants with large tusks are less likely to survive to reproduce

(#3)Which of the following is the outgrip in the cladogram shown in Figure 1?

A. carolinensis

(#4)Based on Figure 1, which of the following would provide the strongest evidence to support the claim that A. valenclenni and A. lineatopus are the two anole species most closely related to A. sagrei?

Analyzing homologous DNA sequences among the species

A common test for liver function involved sprinkling suffer powder onto a sample of urine (mostly water with dissolved bodily waste). Sulfur powder sprinkled on a sample from an individual with impaired liver function will sink because the urine contains a high level of bile salts, while the sulfur powder sprinkled on normal urine samples will float. Which of the following best explains why bile salts cause the sulfur powder to sink?

Bile salts decrease the surface tension of the urine sample

(#2)In anoles, small toe pads are better for gripping irregular surfaces such as the forest floor, and large toe pads are better for gripping smooth surfaces such as leaves. Based on the data in Table 1, if brown anoles are introduced into a forest where green anoles currently live, which of the following predictions about the two species is most likely?

Brown anoles will occupy a different area of the forest green from green anoles which will minimize competition

Ethylene gas is an organic molecule that serves many cell signaling roles in flowering plants. Which of the following best explains how a positive feedback mechanism involving ethylene works?

Cells of ripening fruit produce ethylene, which activates the ripening response in other fruit cells

(#5)Based on the cladogram in Figure 1, which of the following conclusions about the evolution of the anole species is most reasonable?

Each species evolved as a result of different selective pressures

(3)Which of the following best explains the connection between energy, growth, and maintenance of an ordered system in the experiment?

Energy input from light is required for the grass to grow and maintain an ordered structure

Based on the data in Figure 1, which of the following most likely represents the change in energy that occurs when ATP hydrolysis is coupled with the phosphorylation of a substrate?

Line 1 represents ATP hydrolysis, and line 4 represents phosphorylation of a substrate

(2)Which of the following best explains the observed differences in mass between the grass in section I after 14 days and the grass in section III after 21 days?

Mass lost by cell respiration in section III was not replaced by photosynthesis

The human sleep-wake cycle is regulated by melatonin. The synthesis of melatonin is regulated by light exposure (Figure 1). The human body typically develops a sleep-wake rhythm that does not respond quickly to change. Long term exposure to extended periods of bright light after sunset is most likely to affect a person in which of the following ways?

Melatonin synthesis inhibited, and the person will have difficulty sleeping

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

Methyl (CH2) group

A typical bag of fertilizer contains high levels of nitrogen, phosphorous, and potassium but trace amounts of magnesium and calcium. Which of the following best matches the fertilizer component with the molecule in which it will be incorporated by organisms in the area?

Nitrogen will be incorporated into nucleic acids

Which of the following best explains how continuity of genetic information in cells is ensured across generations?

Replication uses a parental strand of DNA as a template to create a new strand of DNA

Which of the following most likely explains how the chromosomes circles in Figure 1 could cause a genetic disorder in the person from which the cells were obtained?

The extra chromosome will affect the levels of RNA transcribed from certain genes and the amount of protein produced from those genes in each cell

(5)Which of the following is a approximate null hypothesis for the student's experiment?

The presence of light has no effect on the mass of the grass

Which of the following best explains how the expression of a eukaryotic gene encoding a protein will differ if the gene is expressed in a prokaryotic cell instead of in a eukaryotic cell?

The protein will be made but will not function because prokaryotes cannot remove introns

(4)Based on the data, which of the following is the most likely effect of a period of increased volcanic activity that significantly decreases the amount go sunlight reaching a particular ecosystem for several years?

There will be a decrease in the population sizes of most species and a decrease in the number of trophic levels

Low concentrations of cadmium in the water negatively affect steelhead trout. In a river community, steelhead trout are part of the trophic structure shown in Figure 1. Which of the following is the most likely immediate effect of an increase in runoff containing cadmium on the trophic structure of the river community?

There will be a large decrease in the trout population, resulting in an increase in damselfly nymphs