1. Which of the following is one limitation of using mathematical models to analyze complex natural systems?
A. Mathematical models are unable to describe accurately some complex natural systems due to unknown variables that influence natural phenomena.
B. Mathematical models use abstract symbols that cannot be applied to the concrete elements that make up natural systems.
C. Mathematical models are used by investigators, but different investigators may use alternative models to study the same system.
D. Mathematical models are useful for describing systems that are static and unchanging, but they cannot incorporate factors that produce change in a system over time.
Correct Response: A.
Explanations: Mathematical models attempt to describe the relationships in natural systems by assigning numbers or equations to known variables. Since a natural system often has parameters that are incompletely understood or have not yet been identified, a mathematical model cannot accurately account for these variables.
2. Which of the following describes the main purpose of the Human Genome Project?
A. to deepen public awareness of the genetic basis of human disease and efforts to treat such diseases
B. to map the nucleotide sequence of the DNA of each human chromosome
C. to develop DNA isolation and labeling techniques to be used in gene analysis
D. to identify every genetically transmitted disease and the gene or genes responsible for each
Correct Response: B.
The primary goal of the Human Genome Project is to determine the sequence of the entire human genome. The information gained from this project may ultimately be applied to many other purposes, such as developing techniques for identifying or treating genetic diseases.
3. A researcher notices frequent occurrences of harmful mutations in sturgeon, Acipenser oxyrhynchus, in a river where manufacturing wastes are regularly being dumped. To begin investigating whether the mutations are caused by the pollution
in the river, the researcher should design an experiment wherein:
A. both mutated and healthy sturgeon from the river are moved to clean water conditions, and mutation frequencies in subsequent generations are measured and compared to river populations.
B. healthy sturgeons are introduced to the river's water conditions, and frequencies of mutations in their offspring are compared to a clean water control group.
C. population levels of the species in the regularly polluted section of the river are monitored for several years and compared to populations several miles downstream from the dump site.
D. other species present in the same habitat are systematically examined for genetic mutations, and the types and frequencies of mutations are recorded.
Correct Response: B. The researcher should begin the investigation by first trying to confirm that the high rate of mutations in the sturgeon are due to something in the water rather than due to a genetic abnormality within this particular population of sturgeon. The best way to do this would be to take a known healthy population of sturgeon and divide it into two groups, putting half of the sturgeon into the river water and the other half into water with no pollutants. If the group put in the river begins to develop harmful mutations and the clean water group does not (assuming all other conditions are kept identical), then it would provide strong evidence that the water conditions are indeed causing the mutations.
4. A botanist conducted a study to examine how soil temperature affects the length of time it takes different varieties of carrot seeds to germinate. The amount of light and humidity levels were the same for all seeds. To report the results in a graph,
which of the following variables should be placed on the horizontal and vertical axes, respectively?
A. variety of carrot—soil temperature
B. soil temperature—length of time to germination
C. amount of light and humidity level—length of time to germination
D. length of time to germination—variety of carrot
Correct Response: B. By convention, the factor being varied in an experiment (independent variable) is plotted on the horizontal axis, while the responding factor (dependent variable) is plotted on the vertical axis. In this experiment, soil temperature is the independent variable, so it should be on the horizontal axis. Length of time to germination is the dependent variable, so it should be on the vertical axis.
5. When antidiuretic hormone (ADH)is released by the pituitary gland it acts on the distal tubules and collecting ducts of the nephrons to increase their permeability to water and promote water retention by the body. This action of ADH on the kidneys has which of the following effects on the body?
A. lowering blood osmolarity
B. raising blood pH
C. lowering blood pressure
D. raising blood glucose
Correct Response: A.
Osmolarity is a measure of the amount of solutes in a given volume of solution. If blood osmolarity rises above a certain level, ADH is released, which causes the kidneys to reabsorb water and return it to the blood. This process effectively lowers the concentration of the solutes in the blood, lowering blood osmolarity.
6. A biologist using the chemical acetone in an experiment should first consult which of the following sources for information pertaining to proper use and laboratory practices to protect against injury or hazards?
A. the methods sections of papers by other researchers who use acetone
B. an emergency first-aid manual
C. the material safety data sheet for acetone
D. officials of the local public health department
Correct Response: C. The law requires that a material safety data sheet must be provided with each chemical purchased from a commercial source. This document includes detailed information about the properties, hazards, and proper use and storage of that specific chemical. This is the most accurate and comprehensive source of information about a particular chemical.
7. Which of the following distinguishes eukaryotic cells from prokaryotic cells?
A. the ability to tolerate the presence of oxygen
B. the presence of membrane-bound organelles
C. the ability to carry out photosynthesis
D. the presence of ribosomes
Correct Response: B. Of the traits listed, the only one that is unique to eukaryotes is the presence of membrane-bound organelles. All of the other traits can be found in certain types of prokaryotes as well.
8. When a person is very active, the CO2 produced by respiration reacts with water
to form carbonic acid, which lowers the tissue's pH. Which of the following best describes the consequence of this pH shift?
A. The carbonic acid accumulates in muscle tissue, causing muscles to ache.
B. The lowered pH interferes with oxygen dissociation, causing the person to feel out of breath.
C. The hydrogen ions that become available combine to form water with any available oxygen.
D. The lowered pH induces hemoglobin to release more O2 for cellular respiration.
Correct Response: D. The conformation of hemoglobin, like that of most proteins, is sensitive to changes in the pH of its surroundings. At a lower pH, the hemoglobin has a lower affinity for oxygen, allowing it to be released to the tissues where it is needed.
9. Which of the following is the summary equation for photosynthesis by green plants?
A. 6ADP + 6Pi + energy→6ATP + 6H2O
B. C6H12O6 + 6O2 + 6H2O→6CO2 + 12H2O + energy
C. 6ATP + 6H2O→6ADP + 6Pi + energy
D. 6CO2 + 12H2O + energy→C6H12O6 + 6O2 + 6H2O
Correct Response: D. The process of photosynthesis in green plants involves the use of light energy to produce sugars (C6H12O6) and oxygen from carbon dioxide and water. Water is both consumed and produced during the process, which accounts for its appearing on both sides of the equation.
10. In eukaryotes, access to certain promoter sites on DNA by RNA polymerase is
restricted by histones. For which of the following processes does this have the most direct consequence?
A. recognition of termination sites
B. control of gene expression
C. translocation of the tRNA along the ribosome
D. formation of the mitotic spindle
Correct Response: B. For a gene to be transcribed and subsequently expressed, the DNA of the promoter must be accessible to RNA polymerase. If histone proteins are binding to a promoter region for a particular gene, then that gene is unavailable for transcription and,therefore, expression.
11. Which of the following is a significant ethical concern associated with the genetic engineering of transgenic agricultural crops?
A. Efficient production of these crops could eventually eliminate the viability of traditional varieties of agricultural produce.
B. Sterility of these crops and patent law would force farmers to buy from the seed manufacturers instead of saving seed.
C. Crops may produce new substances that could harmfully affect humans in ways that are unpredictable.
D. Biodiversity would be enhanced by the large-scale farming these crops allow.
Correct Response: C. One of the most significant concerns that has been voiced about the genetic engineering of agricultural crops involves the process of taking genes for desirable traits (e.g., pest resistance) from another organism and putting them into a crop plant that people consume. This practice could, in some circumstances, result in crop plants forming compounds that might be toxic or to which certain individuals might be allergic.
12. In terms of the cell cycle, cancer cells differ from normal cells in which of the
I. Cancer cells pass through phases of the cell cycle in sequences different from
that of normal cells.
II. Cancer cells do not stop dividing when they come in contact with other cells as normal cells do.
III. Cancer cells are able to divide an indefinite number of times, while normal cells divide a limited number of times.
IV. Cancer cells are more sensitive to changes in external factors than are
normal cells, and alter their division rates accordingly.
A. I and III only
B. II and III only
C. II and IV only
D. I, II, and IV only
Correct Response: B. Control mechanisms typically limit the growth and division of normal cells. One of these control mechanisms is contact inhibition; when normal cells in tissue come in contact with one another, they stop dividing. Another control mechanism is the ability of normal cells to undergo only a finite number of divisions before cell death. Cells that are transformed into cancer cells are freed of these controls and, therefore, divide without restraint.