Which of the following explains most specifically the attraction of water molecules to one another?
A) nonpolar covalent bond
B) polar covalent bond
C) ionic bond
D) hydrogen bond
E) hydrophobic interaction

Answer: D

In the term trace element, the modifier trace means that
A) the element is required in very small amounts.
B) the element can be used as a label to trace atoms through an organism's metabolism.
C) the element is very rare on Earth.
D) the element enhances health but is not essential for the organism's long-term survival.
E) the element passes rapidly through the organism.

Answer: A

Van der Waals interactions result when
A) hybrid orbitals overlap.
B) electrons are not symmetrically distributed in a molecule.
C) molecules held by ionic bonds react with water.
D) two polar covalent bonds react.
E) a hydrogen atom loses an electron.

Answer: B

Which of the following correctly describes chemical equilibrium?
A) Forward and reverse reactions continue with no effect on the concentrations of the reactants and products.
B) Concentrations of products are higher than the concentrations of the reactants.
C) Forward and reverse reactions have stopped so that the concentration of the reactants equals the concentration of the products.
D) Reactions stop only when all reactants have been converted to products.
E) There are equal concentrations of reactants and products, and the reactions have stopped.

Answer: A

In the figure above, how many electrons does nitrogen have in its valence shell?

A) 2
B) 5
C) 7
D) 8
E) 14

Answer: B

What results from the chemical reaction illustrated above?
A) a cation with a net charge of +1
B) a cation with a net charge of -1
C) an anion with a net charge of +1
D) an anion with a net charge of -1
E) a cation with a net charge of +1 and an anion with a net charge of -1

Answer: E

Which one of the atoms shown would be most likely to form an anion with a charge of -1?

Answer: D

Compared with ³¹P, the radioactive isotope ³²P has
A) a different atomic number.
B) a different charge.
C) one more proton.
D) one more electron.
E) one more neutron.

Answer: E

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately

96% of living matter?

1. A) carbon, oxygen, nitrogen, calcium
2. B) carbon, oxygen, phosphorus, hydrogen
3. C) carbon, oxygen, phosphorus, hydrogen
4. D) carbon, hydrogen, nitrogen, oxygen

Answer: D

Liquid water's high specific heat is mainly a consequence of the
A) small size of the water molecules.
B) high specific heat of oxygen and hydrogen atoms.
C) absorption and release of heat when hydrogen bonds break and form.
D) fact that water is a poor heat conductor.
E) higher density of liquid water than solid water (ice).

Answer: C

Which type of bond must be broken for water to vaporize?
A) ionic bonds
B) both hydrogen bonds and ionic bonds
C) polar covalent bonds
D) hydrogen bonds
E) both polar covalent bonds and hydrogen bonds

Answer: D

Why does ice float in liquid water?
A) The high surface tension of liquid water keeps the ice on top.
B) The ionic bonds between the molecules in ice prevent the ice from sinking.
C) Ice always has air bubbles that keep it afloat.
D) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.
E) The crystalline lattice of ice causes it to be denser than liquid water.

Answer: D

You have a freshly prepared 0.1 M solution of glucose in water. Each liter of this solution contains how many glucose molecules?
A) 6.02 × 10²³
B) 3.01 × 10²³
C) 6.02 × 10²⁴
D) 12.04 × 10²³
E) 6.02 × 10²²

Answer: E

What is the pH of a solution with a hydroxyl ion [OH⁻] concentration of 10⁻¹² M?
A) pH 2
B) pH 4
C) pH 10
D) pH 12
E) pH 14

Answer: A

If the pH of a solution is decreased from 9 to 8, it means that the
A) concentration of H⁺ has decreased to one-tenth (1/10) what it was at pH 9.
B) concentration of H⁺ has increased tenfold (10X) compared to what it was at pH 9.
C) concentration of OH⁻ has increased tenfold (10X) compared to what it was at pH 9.
D) concentration of OH⁻ has decreased to one-tenth (1/10) what it was at pH 9.
E) concentration of H⁺ has increased tenfold (10X) and the concentration of OH⁻ has decreased to one-tenth (1/10) what they were at pH 9.

Answer: E

How would acidification of seawater affect marine organisms?
A) Acidification would increase dissolved carbonate concentrations and promote faster growth of corals and shell-building animals.
B) Acidification would decrease dissolved carbonate concentrations and promote faster growth of corals and shell-building animals.
C) Acidification would increase dissolved carbonate concentrations and hinder growth of corals and shell-building animals.
D) Acidification would decrease dissolved carbonate concentrations and hinder growth of corals and shell-building animals.
E) Acidification would increase dissolved bicarbonate concentrations, and cause increased calcification of corals and shellfish.

Answer: D

How many grams of the compound in the figure above would be required to make 1 L of a 0.5 M solution?
(carbon = 12, oxygen = 16, hydrogen = 1)
A) 29
B) 30
C) 60
D) 150
E) 342

Answer: B

The partial negative charge in a molecule of water occurs because
A) the oxygen atom acquires an additional electron.
B) the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus.
C) the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms.
D) the oxygen atom forms hybrid orbitals that distribute electrons unequally around the oxygen nucleus.
E) one of the hydrogen atoms donates an electron to the oxygen atom.

Answer: B

Which of the following effects is produced by the high surface tension of water?
A) Lakes don't freeze solid in winter, despite low temperatures.
B) A water strider can walk across the surface of a small pond.
C) Organisms resist temperature changes, although they give off heat due to chemical reactions.
D) Evaporation of sweat from the skin helps to keep people from overheating.
E) Water flows upward from the roots to the leaves in plants.

Answer: B

Hydrophobic substances such as vegetable oil are
A) nonpolar substances that repel water molecules.
B) nonpolar substances that have an attraction for water molecules.
C) polar substances that repel water molecules.
D) polar substances that have an affinity for water.
E) charged molecules that hydrogen-bond with water molecules

Answer: A

What is the hydrogen ion [H⁺] concentration of a solution of pH 8?
A) 8 M
B) 8 x 10⁻⁶ M
C) 0.01 M
D) 10⁻⁸ M
E) 10⁻⁶ M

Answer: D

If the pH of a solution is increased from pH 5 to pH 7, it means that the
A) concentration of H⁺ is twice (2X) what it was at pH 5.
B) concentration of H⁺ is one-half (1/2) what it was at pH 5.
C) concentration of OH⁻ is 100 times greater than what it was at pH 5.
D) concentration of OH⁻ is one-hundredth (0.01X) what it was at pH 5.
E) concentration of H⁺ is 100 times greater and the concentration of OH⁻ is one-hundredth what they were at pH 5.

Answer: C

The element present in all organic molecules is
A) hydrogen.
B) oxygen.
C) carbon.
D) nitrogen.
E) phosphorus.

Answer: C

Hermann Kolbe's synthesis of an organic compound, acetic acid, from inorganic substances that had been prepared directly from pure elements was a significant milestone for what reason?
A) It solved an industrial shortage of acetic acid.
B) It proved that organic compounds could be synthesized from inorganic compounds.
C) It disproved the concept of vitalism.
D) It showed that life originated from simple inorganic chemicals.
E) It proved that organic compounds could be synthesized from inorganic compounds and disproved the concept of vitalism.

Answer: E

Which of the following statements correctly describes cis-trans isomers?
A) They have variations in arrangement around a double bond.
B) They have an asymmetric carbon that makes them mirror images.
C) They have the same chemical properties.
D) They have different molecular formulas.
E) Their atoms and bonds are arranged in different sequences.

Answer: A

Compared to a hydrocarbon chain where all the carbon atoms are linked by single bonds, a hydrocarbon chain with the same number of carbon atoms, but with one or more double bonds, will
A) be more flexible in structure.
B) be more constrained in structure.
C) be more polar.
D) have more hydrogen atoms.
E) have fewer structurally distinct isomers.

Answer: B

Organic molecules with only hydrogens and five carbon atoms can have different structures in all of the following ways except
A) by branching of the carbon skeleton.
B) by varying the number of double bonds between carbon atoms.
C) by varying the position of double bonds between carbon atoms.
D) by forming a ring.
E) by forming enantiomers.

Answer: E

Which two functional groups are always found in amino acids?

A) ketone and methyl
B) carbonyl and amino
C) carboxyl and amino
D) amino and sulfhydryl
E) hydroxyl and carboxyl

Answer: C

Testosterone and estradiol are
A) soluble in water.
B) structural isomers of each other.
C) proteins.
D) lipids.
E) enantiomers of each other.

Answer: B

Three or four of the following illustrations depict different structural isomers of the organic compound with molecular formula C₆H₁₄. For clarity, only the carbon skeletons are shown; hydrogen atoms that would be attached to the carbons have been omitted. Which one, if any, is NOT a structural isomer of this compound?

Answer: C

Which functional group(s) shown above is (are) present in all amino acids?
A) A and B
B) B and D
C) C only
D) D only
E) C and D

Answer: E

Which functional group is not present in this molecule?
A) carboxyl
B) sulfhydryl
C) hydroxyl
D) amino

Answer: B

Why are hydrocarbons insoluble in water?
A) The majority of their bonds are polar covalent carbon-to-hydrogen linkages.
B) The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.
C) They are hydrophilic.
D) They exhibit considerable molecular complexity and diversity.
E) They are lighter than water.

Answer: B

Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that

A) have identical chemical formulas but differ in the branching of their carbon skeletons.
B) are mirror images of one another.
C) exist in either linear chain or ring forms.
D) differ in the location of their double bonds.
E) differ in the arrangement of atoms around their double bonds.

Answer: B

The two molecules shown in the figure above are best described as
A) optical isomers.
B) enantiomers.
C) structural isomers.
D) cis-trans isomers.
E) chain length isomers.

Answer: C

The two molecules shown in the figure above are best described as

A) enantiomers.
B) radioactive isotopes.
C) structural isomers.
D) nonisotopic isomers.
E) cis-trans isomers.

Answer: E

Which of these molecules is not formed by dehydration reactions?
A) fatty acids
B) disaccharides
C) DNA
D) protein
E) amylose

Answer: A

Which of the following is not a polymer?
A) glucose
B) starch
C) cellulose
D) chitin
E) DNA

Answer: A

On food packages, to what does the term insoluble fiber refer?
A) cellulose
B) polypeptides
C) starch
D) amylopectin
E) chitin

Answer: A

All of the following contain amino acids except
A) hemoglobin.
B) cholesterol.
C) antibodies.
D) enzymes.
E) insulin.

Answer: B

What aspects of protein structure are stabilized or assisted by hydrogen bonds?
A) primary structure
B) secondary structure
C) tertiary structure
D) quaternary structure
E) secondary, tertiary, and quaternary structures, but not primary structure

Answer: E

Which bonds are created during the formation of the primary structure of a protein?
A) peptide bonds
B) hydrogen bonds
C) disulfide bonds
D) phosphodiester bonds
E) peptide bonds, hydrogen bonds, and disulfide bonds

Answer: A

What maintains the secondary structure of a protein?
A) peptide bonds
B) hydrogen bonds between the amino group of one peptide bond and the carboxyl group of another peptide bond
C) disulfide bonds
D) hydrophobic interactions
E) hydrogen bonds between the R groups

Answer: B

What is the structure shown in the figure?

1. A) pentose molecule
2. B) fatty acid molecule
3. C) steroid molecule
4. D) oligosaccharide molecule
5. E) phospholipid molecule

Answer: C

Which class of biological polymer has the greatest functional variety?
A) polysaccharides
B) proteins
C) DNA
D) RNA

Answer: B

The structural level of a protein least affected by a disruption in hydrogen bonding is the
A) primary level.
B) secondary level.
C) tertiary level.
D) quaternary level.
E) All structural levels are equally affected.

Answer: A

Which of the following statements is true for the class of biological molecules known as lipids?
A) They are insoluble in water.
B) They are made from glycerol, fatty acids, and phosphate.
C) They contain less energy than proteins and carbohydrates.
D) They are made by dehydration reactions.
E) They contain nitrogen.

Answer: A

There are 20 different amino acids. What makes one amino acid different from another?
A) different side chains (R groups) attached to a carboxyl carbon
B) different side chains (R groups) attached to the amino groups
C) different side chains (R groups) attached to an α carbon
D) different structural and optical isomers
E) different asymmetric carbons

Answer: C

Dehydration reactions are used in forming which of the following compounds?
A) triacylglycerides
B) polysaccharides
C) proteins
D) triacylglycerides and proteins only
E) triacylglycerides, polysaccharides, and proteins

Answer: E

The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that
A) plant cells are capable of having a much higher surface-to-volume ratio than animal cells.
B) plant cells have a much more highly convoluted (folded) plasma membrane than animal cells.
C) plant cells contain a large vacuole that reduces the volume of the cytoplasm.
D) animal cells are more spherical, whereas plant cells are elongated.
E) plant cells can have lower surface-to-volume ratios than animal cells because plant cells synthesize their own nutrients.

Answer: C

Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
A) lipids
B) glycogen
C) proteins
D) cellulose
E) nucleic acids

Answer: C

A cell with a predominance of free ribosomes is most likely
A) producing primarily proteins for secretion.
B) producing primarily cytoplasmic proteins.
C) constructing an extensive cell wall or extracellular matrix.
D) digesting large food particles.
E) enlarging its vacuole.

Answer: B

Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. Which of the following organelles contains these hydrolytic enzymes in animal cells?
A) chloroplast
B) lysosome
C) central vacuole
D) peroxisome
E) glyoxysome

Answer: B

One of the key innovations in the evolution of eukaryotes from a prokaryotic ancestor is the endomembrane system. What eukaryotic organelles or features might have evolved as a part of, or as an elaboration of, the endomembrane system?
A) plasma membrane
B) chloroplasts
C) mitochondria
D) nuclear envelope
E) none of these

Answer: D

If an individual has abnormal microtubules, due to a hereditary condition, in which organs or tissues would you expect dysfunction?
A) limbs, hearts, areas with a good deal of contraction
B) microvilli, alveoli, and glomeruli: cellular projections that increase surface area
C) all ducts, such as those from salivary or sebaceous glands, that transport fluids
D) sperm, larynx, and trachea: cells and tissues that contain flagella or cilia
E) phagocytic cells and white blood cells that exhibit amoeboid movement

Answer: D

The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?
A) They must block water and small molecules in order to regulate the exchange of matter and energy with their environment.
B) They must permit information transfer between the cell's cytoplasm and the nucleus.
C) They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume.
D) They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell.
E) They are composed of a mixture of lipids and carbohydrates.

Answer: D

A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in its
A) nuclear lamina and nuclear matrix.
B) nuclear matrix and extracellular matrix.
C) mitochondria and Golgi apparatus.
D) Golgi apparatus and extracellular matrix.
E) nuclear pores and secretory vesicles.

Answer: D

In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and
A) combine the hydrogen with water molecules to generate hydrogen peroxide.
B) use the hydrogen to break down hydrogen peroxide.
C) transfer the hydrogen to the mitochondria.
D) transfer the hydrogen to oxygen molecules to generate hydrogen peroxide.

Answer: D

The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following?
A) gap junctions
B) the nucleus
C) DNA and RNA
D) integrins
E) plasmodesmata

Answer: D

Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?

A) peroxisomes
B) desmosomes
C) gap junctions
D) extracellular matrix
E) tight junctions

Answer: C

What types of proteins are not synthesized in the rough ER?
A) endoplasmic reticulum proteins
B) extracellular matrix proteins
C) secreted proteins
D) mitochondrial proteins
E) plasma membrane proteins

Answer: D

Which type of organelle is found in plant cells but not in animal cells?
A) ribosomes
B) mitochondria
C) nuclei
D) plastids
E) none of these

Answer: D

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?
A) by increasing the percentage of unsaturated phospholipids in the membrane
B) by increasing the percentage of cholesterol molecules in the membrane
C) by decreasing the number of hydrophobic proteins in the membrane
D) by cotransport of glucose and hydrogen
E) by using active transport

Answer: A

Water passes quickly through cell membranes because
A) the bilayer is hydrophilic.
B) it moves through hydrophobic channels.
C) water movement is tied to ATP hydrolysis.
D) it is a small, polar, charged molecule.
E) it moves through aquaporins in the membrane.

Answer: E

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in
A) peroxisomes.
B) lysosomes.
C) Golgi vesicles.
D) vacuoles.
E) secretory vesicles.

Answer: B

In the small airways of the lung, a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung. One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane. How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid?
A) Sodium ion transport will increase; higher osmotic potential will increase airway surface liquid volume.
B) Sodium ion transport will increase; higher osmotic potential will decrease airway surface liquid volume.
C) Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume.
D) Sodium ion transport will decrease; lower osmotic potential will increase the airway surface liquid volume.
E) Sodium ion transport will be unaffected; lack of chloride transport still reduces osmotic potential and decreases the airway surface liquid volume.

Answer: C

A protein that spans the phospholipid bilayer one or more times is
A) a transmembrane protein.
B) an integral protein.
C) a peripheral protein.
D) an integrin.
E) a glycoprotein.

Answer: A

What kinds of molecules pass through a cell membrane most easily?
A) large and hydrophobic
B) small and hydrophobic
C) large polar
D) ionic
E) monosaccharides such as glucose

Answer: B

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
A) CO₂
B) an amino acid
C) glucose
D) K⁺
E) starch

Answer: A

Which of the following statements is correct about diffusion?
A) It is very rapid over long distances.
B) It requires an expenditure of energy by the cell.
C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
E) It requires integral proteins in the cell membrane.

Answer: C

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?
A) Water will leave the cells, causing them to shrivel and collapse.
B) NaCl will be exported from the red blood cells by facilitated diffusion.
C) The blood cells will take up water, swell, and eventually burst.
D) NaCl will passively diffuse into the red blood cells.
E) The blood cells will expend ATP for active transport of NaCl into the cytoplasm.

Answer: A

When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
A) The cell will burst.
B) The cell membrane will lyse.
C) Plasmolysis will shrink the interior.
D) The cell will become flaccid.
E) The cell will become turgid.

Answer: E

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
A) simple diffusion
B) phagocytosis
C) active transport pumps
D) exocytosis
E) facilitated diffusion

Answer: E

The sodium-potassium pump is called an electrogenic pump because it
A) pumps equal quantities of Na⁺ and K⁺ across the membrane.
B) pumps hydrogen ions out of the cell.
C) contributes to the membrane potential.
D) ionizes sodium and potassium atoms.
E) is used to drive the transport of other molecules against a concentration gradient.

Answer: C

The movement of potassium into an animal cell requires
A) low cellular concentrations of sodium.
B) high cellular concentrations of potassium.
C) an energy source such as ATP.
D) a cotransport protein.
E) a potassium channel protein.

Answer: C

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
A) catalysis
B) metabolism
C) anabolism
D) dehydration
E) catabolism

Answer: E

Which of the following is (are) true for anabolic pathways?
A) They do not depend on enzymes.
B) They are usually highly spontaneous chemical reactions.
C) They consume energy to build up polymers from monomers.
D) They release energy as they degrade polymers to monomers.
E) They consume energy to decrease the entropy of the organism and its environment.

Answer: C

Which of the following is a statement of the first law of thermodynamics?
A) Energy cannot be created or destroyed.
B) The entropy of the universe is decreasing.
C) The entropy of the universe is constant.
D) Kinetic energy is stored energy that results from the specific arrangement of matter.
E) Energy cannot be transferred or transformed.

Answer: A

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
A) Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.
B) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe.
C) Living organisms do not follow the laws of thermodynamics.
D) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
E) Living organisms are able to transform energy into entropy.

Answer: D

Which of the following types of reactions would decrease the entropy within a cell?
A) anabolic reactions
B) hydrolysis
C) respiration
D) digestion
E) catabolic reactions

Answer: A

The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct?
A) ΔS is the change in enthalpy, a measure of randomness.
B) ΔH is the change in entropy, the energy available to do work.
C) ΔG is the change in free energy.
D) T is the temperature in degrees Celsius.

Answer: C

When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?
A) The phosphate is released as an excretory waste.
B) The phosphate can only be used to regenerate more ATP.
C) The phosphate can be added to water and excreted as a liquid.
D) The phosphate may be incorporated into any molecule that contains phosphate.
E) It enters the nucleus to affect gene expression.

Answer: D

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
A) entropy.
B) activation energy.
C) endothermic level.
D) equilibrium point.
E) free-energy content.

Answer: B

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
A) by binding at the active site of the enzyme
B) by changing the shape of the enzyme's active site
C) by changing the free energy change of the reaction
D) by acting as a coenzyme for the reaction
E) by decreasing the activation energy of the reaction

Answer: B

Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid.

What is malonic acid's role with respect to succinate dehydrogenase?
A) It is a competitive inhibitor.
B) It blocks the binding of fumarate.
C) It is a noncompetitive inhibitor.
D) It is able to bind to succinate.
E) It is an allosteric regulator.

Answer: A

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to
A) add more of the enzyme.
B) heat the solution to 90°C.
C) add more substrate.
D) add an allosteric inhibitor.
E) add a noncompetitive inhibitor.

Answer: A

Which of the following is the smallest closed system?
A) a cell
B) an organism
C) an ecosystem
D) Earth
E) the universe

Answer: E

A system at chemical equilibrium
A) consumes energy at a steady rate.
B) releases energy at a steady rate.
C) consumes or releases energy, depending on whether it is exergonic or endergonic.
D) has zero kinetic energy.
E) can do no work.

Answer: E

Which of the following statements describes NAD⁺?
A) NAD⁺ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
B) NAD⁺ has more chemical energy than NADH.
C) NAD⁺ is oxidized by the action of hydrogenases.
D) NAD⁺ can donate electrons for use in oxidative phosphorylation.
E) In the absence of NAD⁺, glycolysis can still function.

Answer: A

Why are carbohydrates and fats considered high energy foods?
A) They have a lot of oxygen atoms.
B) They have no nitrogen in their makeup.
C) They can have very long carbon skeletons.
D) They have a lot of electrons associated with hydrogen.
E) They are easily reduced.

Answer: D

In glycolysis, for each molecule of glucose oxidized to pyruvate
A) two molecules of ATP are used and two molecules of ATP are produced.
B) two molecules of ATP are used and four molecules of ATP are produced.
C) four molecules of ATP are used and two molecules of ATP are produced.
D) two molecules of ATP are used and six molecules of ATP are produced.
E) six molecules of ATP are used and six molecules of ATP are produced.

Answer: B

What is proton-motive force?
A) the force required to remove an electron from hydrogen
B) the force exerted on a proton by a transmembrane proton concentration gradient
C) the force that moves hydrogen into the intermembrane space
D) the force that moves hydrogen into the mitochondrion
E) the force that moves hydrogen to NAD⁺

Answer: B

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
A) It allows for an increased rate of glycolysis.
B) It allows for an increased rate of the citric acid cycle.
C) It increases the surface for oxidative phosphorylation.
D) It increases the surface for substrate-level phosphorylation.
E) It allows the liver cell to have fewer mitochondria.

Answer: C

Which statement best supports the hypothesis that glycolysis is an ancient metabolic pathway that originated before the last universal common ancestor of life on Earth?
A) Glycolysis is widespread and is found in the domains Bacteria, Archaea, and Eukarya.
B) Glycolysis neither uses nor needs O₂.
C) Glycolysis is found in all eukaryotic cells.
D) The enzymes of glycolysis are found in the cytosol rather than in a membrane-enclosed organelle.
E) Ancient prokaryotic cells, the most primitive of cells, made extensive use of glycolysis long before oxygen was present in Earth's atmosphere.

Answer: A

What is the purpose of beta oxidation in respiration?
A) oxidation of glucose
B) oxidation of pyruvate
C) feedback regulation
D) control of ATP accumulation
E) breakdown of fatty acids

Answer: E

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
A) oxidation of glucose and other organic compounds.
B) flow of electrons down the electron transport chain.
C) affinity of oxygen for electrons.
D) H⁺ concentration across the membrane holding ATP synthase.
E) transfer of phosphate to ADP.

Answer: D

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
A) the citric acid cycle
B) the electron transport chain
C) glycolysis
D) synthesis of acetyl CoA from pyruvate
E) reduction of pyruvate to lactate

Answer: C

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
A) oxygen.
B) water.
C) NAD⁺.
D) pyruvate.
E) ADP.

Answer: A

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
A) The pH of the matrix increases.
B) ATP synthase pumps protons by active transport.
C) The electrons gain free energy.
D) The cytochromes phosphorylate ADP to form ATP.
E) NAD⁺ is oxidized.

Answer: A

Which process in eukaryotic cells will proceed normally whether oxygen (O₂) is present or absent?
A) electron transport
B) glycolysis
C) the citric acid cycle
D) oxidative phosphorylation
E) chemiosmosis

Answer: B

A molecule that is phosphorylated
A) has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.
B) has a decreased chemical reactivity; it is less likely to provide energy for cellular work.
C) has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate.
D) has an increased chemical potential energy; it is primed to do cellular work.
E) has less energy than before its phosphorylation and therefore less energy for cellular work.

Answer: D

In any ecosystem, terrestrial or aquatic, what group(s) is (are) always necessary?
A) autotrophs and heterotrophs
B) producers and primary consumers
C) photosynthesizers
D) autotrophs
E) green plants

Answer: D

In autotrophic bacteria, where are the enzymes located that can carry on carbon fixation (reduction of carbon dioxide to carbohydrate)?
A) in chloroplast membranes
B) in chloroplast stroma
C) in the cytosol
D) in the nucleoid
E) in the infolded plasma membrane

Answer: C

A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?
A) red and yellow
B) blue and violet
C) green and yellow
D) blue, green, and red
E) green, blue, and yellow

Answer: B

Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will have the most direct effect on which of the following processes?
A) the splitting of water
B) the absorption of light energy by chlorophyll
C) the flow of electrons from photosystem II to photosystem I
D) the synthesis of ATP
E) the reduction of NADP⁺

Answer: D

In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during
A) photosynthesis only.
B) respiration only.
C) both photosynthesis and respiration.
D) neither photosynthesis nor respiration.
E) photorespiration only.

Answer: C

In a plant leaf, the reactions that produce NADH occur in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis.

Answer: D

Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?
A) The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, Pi, and NADP⁺ to the light reactions.
B) The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle, and the cycle provides water and electrons to the light reactions.
C) The light reactions supply the Calvin cycle with CO₂ to produce sugars, and the Calvin cycle supplies the light reactions with sugars to produce ATP.
D) The light reactions provide the Calvin cycle with oxygen for electron flow, and the Calvin cycle provides the light reactions with water to split.
E) There is no relationship between the light reactions and the Calvin cycle.

Answer: A

A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide.

Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed. What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?
A) full-spectrum white light
B) green light
C) a mixture of blue and red light
D) yellow light
E) UV light

Answer: C

Where does the Calvin cycle take place?
A) stroma of the chloroplast
B) thylakoid membrane
C) cytoplasm surrounding the chloroplast
D) interior of the thylakoid (thylakoid space)
E) outer membrane of the chloroplast

Answer: A

What are the products of linear photophosphorylation?
A) heat and fluorescence
B) ATP and P700
C) ATP and NADPH
D) ADP and NADP
E) P700 and P680

Answer: C

For anaphase to begin, which of the following must occur?

A) Chromatids must lose their kinetochores.
B) Cohesin must attach the sister chromatids to each other.
C) Cohesin must be cleaved enzymatically.
D) Kinetochores must attach to the metaphase plate.
E) Spindle microtubules must begin to depolymerize.

Answer: C

At the M phase checkpoint, the complex allows for what to occur?
A) Separase enzyme cleaves cohesins and allows chromatids to separate.
B) Cohesins alter separase to allow chromatids to separate.
C) Kinetochores are able to bind to spindle microtubules.
D) All microtubules are made to bind to kinetochores.
E) Daughter cells are allowed to pass into G₁.

Answer: A

Which number represents DNA synthesis?
A) I
B) II
C) III
D) IV
E) V

Answer: B

Reduction of oxygen to form water occurs during
A) photosynthesis only.
B) respiration only.
C) both photosynthesis and respiration.
D) neither photosynthesis nor respiration.
E) photorespiration only.

Answer: B

The reactions that produce molecular oxygen (O₂) take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but are not part of photosynthesis.

Answer: A

What is the primary function of the Calvin cycle?
A) use ATP to release carbon dioxide
B) use NADPH to release carbon dioxide
C) split water and release oxygen
D) transport RuBP out of the chloroplast
E) synthesize simple sugars from carbon dioxide

Answer: E

The centromere is a region in which

A) chromatids remain attached to one another until anaphase.
B) metaphase chromosomes become aligned at the metaphase plate.
C) chromosomes are grouped during telophase.
D) the nucleus is located prior to mitosis.
E) new spindle microtubules form at either end.

Answer: A

Which of the following describe(s) cyclin-dependent kinase (Cdk)?

A) Cdk is inactive, or "turned off," in the presence of cyclin.
B) Cdk is present throughout the cell cycle.
C) Cdk is an enzyme that attaches phosphate groups to other proteins.
D) Cdk is inactive, or "turned off," in the presence of cyclin and it is present throughout the cell cycle.
E) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.

Answer: E

Which of the following most accurately describes a cyclin?

A) It is present in similar concentrations throughout the cell cycle.
B) It is activated to phosphorylate by complexing with a Cdk.
C) It decreases in concentration when MPF activity increases.
D) It activates a Cdk molecule when it is in sufficient concentration.
E) It activates a Cdk when its concentration is decreased.

Answer: D

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can therefore be assayed to track their incorporation. In a set of experiments, a student—faculty research team used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times.
Which of the following questions might be answered by such a method?

A) How many cells are produced by the culture per hour?
B) What is the length of the S phase of the cell cycle?
C) When is the S chromosome synthesized?
D) How many picograms of DNA are made per cell cycle?
E) When do spindle fibers attach to chromosomes?

Answer: B

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can therefore be assayed to track their incorporation. In a set of experiments, a student—faculty research team used labeled T nucleotides and introduced these into the culture of dividing human cells at specific times.

The research team used the setup to study the incorporation of labeled nucleotides into a culture of lymphocytes and found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. They concluded that
A) the presence of the pathogen made the experiment too contaminated to trust the results.
B) their tissue culture methods needed to be relearned.
C) infection causes lymphocytes to divide more rapidly.
D) infection causes cell cultures in general to reproduce more rapidly.
E) infection causes lymphocyte cultures to skip some parts of the cell cycle.

Answer: C

One difference between cancer cells and normal cells is that cancer cells

A) are unable to synthesize DNA.
B) are arrested at the S phase of the cell cycle.
C) continue to divide even when they are tightly packed together.
D) cannot function properly because they are affected by density-dependent inhibition.
E) are always in the M phase of the cell cycle.

Answer: C

Which of the following does not occur during mitosis?
A) condensation of the chromosomes
B) replication of the DNA
C) separation of sister chromatids
D) spindle formation
E) separation of the spindle poles

Answer: B

A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in
A) G₁.
B) G₂.
C) prophase.
D) metaphase.
E) anaphase.

Answer: A

At which phase are centrioles beginning to move apart in animal cells?

A) telophase
B) anaphase
C) prometaphase
D) metaphase
E) prophase

Answer: E

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?

A) centromere
B) centrosome
C) centriole
D) chromatid
E) kinetochore

Answer: B

In the human species, all somatic cells have 46 chromosomes. Which of the following can also be true?
A) A plant species (privet shrubs) has 46 chromosomes per cell.
B) Some adult humans have 69 chromosomes per cell.
C) Some adult humans have 23 chromosomes per cell.
D) A certain fungal species has only one chromosome per cell.
E) A certain bacterial species has 23 chromosomes.

Answer: A

The human X and Y chromosomes
A) are both present in every somatic cell of males and females alike.
B) are of approximately equal size and number of genes.
C) are almost entirely homologous, despite their different names.
D) include genes that determine an individual's sex.
E) include only genes that govern sex determination.

Answer: D

Which of the following is true of a species that has a chromosome number of 2n = 16?

A) The species is diploid with 32 chromosomes per cell.
B) The species has 16 sets of chromosomes per cell.
C) Each cell has eight homologous pairs.
D) During the S phase of the cell cycle there will be 32 separate chromosomes.
E) A gamete from this species has four chromosomes.

Answer: C

Referring to a plant's sexual life cycle, which of the following terms describes the process that leads directly to the formation of gametes?
A) sporophyte meiosis
B) gametophyte mitosis
C) gametophyte meiosis
D) sporophyte mitosis
E) alternation of generations

Answer: B

Which of the following best describes a karyotype?

A) a pictorial representation of all the genes for a species
B) a display of each of the chromosomes of a single cell
C) the combination of all the maternal and paternal chromosomes of a species
D) the collection of all the chromosomes in an individual organism
E) a photograph of all the cells with missing or extra chromosomes

Answer: B

In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?
A) Length and position of the centromere only.
B) Length, centromere position, and staining pattern only.
C) Length, centromere position, staining pattern, and traits coded for by their genes.
D) Length, centromere position, staining pattern, and DNA sequences.
E) They have nothing in common except they are X-shaped.

Answer: C

A cell divides to produce two daughter cells that are genetically different.
A) The statement is true for mitosis only.
B) The statement is true for meiosis I only.
C) The statement is true for meiosis II only.
D) The statement is true for mitosis and meiosis I.
E) The statement is true for mitosis and meiosis II.

Answer: B

Independent assortment of chromosomes occurs.
A) The statement is true for mitosis only.
B) The statement is true for meiosis I only.
C) The statement is true for meiosis II only.
D) The statement is true for mitosis and meiosis I.
E) The statement is true for mitosis and meiosis II.

Answer: B

A tetrad includes which of the following sets of DNA strands?
A) two single-stranded chromosomes that have synapsed
B) two sets of sister chromatids that have synapsed
C) four sets of sister chromatids
D) four sets of unique chromosomes
E) eight sets of sister chromatids

Answer: B

To visualize and identify meiotic cells at metaphase with a microscope, what would you look for?
A) sister chromatids grouped at the poles
B) individual chromosomes all at the cell's center
C) an uninterrupted spindle array
D) the synaptonemal complex
E) tetrads all aligned at the cell's center

Answer: E

For the following question, match the key event of meiosis with the stages listed below.

Tetrads of chromosomes are aligned at the equator of the spindle; alignment determines independent assortment.

I. Prophase I V. Prophase II
II. Metaphase I VI. Metaphase II
III. Anaphase I VII. Anaphase II
IV. Telophase I VIII. Telophase II

A) I
B) II
C) IV
D) VI
E) VIII

Answer: B

Which of the life cycles is typical for most fungi and some protists?
A) I only
B) II only
C) III only
D) I and II
E) I and III

Answer: B

After telophase I of meiosis, the chromosomal makeup of each daughter cell is
A) diploid, and the chromosomes are each composed of a single chromatid.
B) diploid, and the chromosomes are each composed of two chromatids.
C) haploid, and the chromosomes are each composed of a single chromatid.
D) haploid, and the chromosomes are each composed of two chromatids.
E) tetraploid, and the chromosomes are each composed of two chromatids.

Answer: D

Why did Mendel continue some of his experiments to the F₂ or F₃ generation?

A) to obtain a larger number of offspring on which to base statistics
B) to observe whether or not a recessive trait would reappear
C) to observe whether or not the dominant trait would reappear
D) to distinguish which alleles were segregating
E) to be able to describe the frequency of recombination

Answer: B

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?
A) incomplete dominance
B) multiple alleles
C) pleiotropy
D) epistasis
E) codominance

Answer: C

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?
A) the knowledge that multiple alleles are involved
B) the allele for blue hydrangea being completely dominant
C) the alleles being codominant
D) the fact that a mutation has occurred
E) environmental factors such as soil pH

Answer: E

Which of the following provides an example of epistasis?

A) Recessive genotypes for each of two genes (aabb) results in an albino corn snake.
B) The allele b17 produces a dominant phenotype, although b1 through b16 do not.
C) In rabbits and many other mammals, one genotype (cc) prevents any fur color from developing.
D) In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes.
E) In cacti, there are several genes for the type of spines.

Answer: C

How could you best predict the maximum number of alleles for a single gene whose polypeptide product is known?
A) Search the population for all phenotypic variants of this polypeptide.
B) Count the number of amino acids in the polypeptide.
C) Mate all known genotypes and collect all possible offspring different from the parents.
D) Measure the rate of new mutations in the species and estimate the number since it first evolved.
E) Count the number of DNA nucleotides that are in the code for the polypeptides.

Answer: E

One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?

A) The mother carries the gene but does not express it at all.
B) One of the parents has very mild expression of the gene.
C) The condition skipped a generation in the family.
D) The child has a different allele of the gene than the parents.

Answer: B

In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in Figure 14.1, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

37) Which of the boxes marked 1-4 correspond to plants with dark leaves?
A) 1 only
B) 1 and 2
C) 2 and 3
D) 4 only
E) 1, 2, and 3

Answer: E

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F₁ individuals have red, axial flowers. The genes for flower color and location assort independently.

If 1,000 F₂ offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?
A) 65
B) 190
C) 250
D) 565
E) 750

Answer: B

Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F₁ individuals have red, axial flowers. The genes for flower color and location assort independently.

Among the F₂ offspring, what is the probability of plants with white axial flowers?
A) 9/16
B) 1/16
C) 3/16
D) 1/8
E) 1/4

Answer: C

Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes ocular problems, such as lens dislocation. Which of the following would you conclude about Marfan syndrome from this information?
A) It is recessive.
B) It is dominant.
C) It has a late age of onset (> 60).
D) It is pleiotropic.
E) It is epistatic.

Answer: D

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

Answer: C

Which of the following describes the ability of a single gene to have multiple phenotypic effects?
A) incomplete dominance
B) multiple alleles
C) pleiotropy
D) epistasis

Answer: C

Which of the following is an example of polygenic inheritance?
A) pink flowers in snapdragons
B) the ABO blood group in humans
C) Huntington's disease in humans
D) white and purple flower color in peas
E) skin pigmentation in humans

Answer: E

Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early 20th century?

A) Individuals inherit particular chromosomes attached to genes.
B) Mendelian genes are at specific loci on the chromosome and in turn segregate during meiosis.
C) Homologous chromosomes give rise to some genes and crossover chromosomes to other genes.
D) No more than a single pair of chromosomes can be found in a healthy normal cell.
E) Natural selection acts on certain chromosome arrays rather than on genes.

Answer: B

Thomas Hunt Morgan's choice of Drosophila melanogaster has been proven to be useful even today. Which of the following has/have continued to make it a most useful species?

I. its four pairs of chromosomes
II. a very large number of visible as well as biochemically mutant phenotypes
III. easy and inexpensive maintenance
IV. short generation time and large number of offspring

A) I and IV only
B) II and III only
C) I, II, and III only
D) II, III, and IV only
E) I, II, III, IV, and V

Answer: E

Calico cats are female because
A) the males die during embryonic development.
B) a male inherits only one of the two X-linked genes controlling hair color.
C) the Y chromosome has a gene blocking orange coloration.
D) only females can have Barr bodies.
E) multiple crossovers on the Y chromosome prevent orange pigment production.

Answer: B

Duchenne muscular dystrophy (DMD) is caused by a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition?

A) Women can never have this condition.
B) One-half of the daughters of an affected man could have this condition.
C) One-fourth of the children of an affected father and a carrier mother could have this condition.
D) Very rarely would a woman have this condition; the condition would be due to a chromosome error.
E) Only if a woman is XXX could she have this condition.

Answer: D

Which of the following statements is true of linkage?
A) The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.
B) The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 100%.
C) All of the traits that Mendel studied–seed color, pod shape, flower color, and others–are due to genes linked on the same chromosome.
D) Linked genes are found on different chromosomes.
E) Crossing over occurs during prophase II of meiosis.

Answer: A

Why does recombination between linked genes continue to occur?
A) Recombination is a requirement for independent assortment.
B) Recombination must occur or genes will not assort independently.
C) New allele combinations are acted upon by natural selection.
D) The forces on the cell during meiosis II always result in recombination.
E) Without recombination there would be an insufficient number of gametes.

Answer: C

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?
A) The frequency of crossing over varies along the length of the chromosome.
B) The relationship between recombination frequency and map units is different in every individual.
C) Physical distances between genes change during the course of the cell cycle.
D) The gene order on the chromosomes is slightly different in every individual.
E) Linkage map distances are identical between males and females.

Answer: A

A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4 that has been exchanged with a portion of his chromosome 12. Although he is normal because his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?

A) 1/4 will be normal, 1/4 will have the translocation, and 1/2 will have duplications and deletions.
B) All will carry the same translocation as the father.
C) None will carry the translocation since abnormal sperm will die.
D) His sperm will be sterile and the couple might consider adoption.
E) 1/2 will be normal and the rest will have the father's translocation.

Answer: A

Which of the following is true of aneuploidies in general?

A) A monosomy is more frequent than a trisomy.
B) 45 X is the only known human live-born monosomy.
C) Some human aneuploidies have selective advantage in some environments.
D) Of all human aneuploidies, only Down syndrome is associated with mental retardation.
E) An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.

Answer: B

Mitochondrial DNA is primarily involved in coding for proteins needed for electron transport. Therefore, in which body systems would you expect most mitochondrial gene mutations to be exhibited?
A) the immune system and the blood
B) the excretory and respiratory systems
C) the skin and senses
D) the nervous and muscular systems
E) the circulation system

Answer: D

Sex determination in mammals is due to the SRY region of the Y chromosome. An abnormality of this region could allow which of the following to have a male phenotype?
A) Turner syndrome, 45, X
B) translocation of SRY to an autosome of a 46, XX individual
C) a person with an extra X chromosome
D) a person with one normal and one shortened (deleted) X
E) Down syndrome, 46, XX

Answer: B

An inversion in a human chromosome often results in no demonstrable phenotypic effect in the individual. What else may occur?
A) There may be deletions later in life.
B) Some abnormal gametes may be formed.
C) There is an increased frequency of mutation.
D) All inverted chromosomes are deleted.
E) The individual is more likely to get cancer.

Answer: B

What is the source of the extra chromosome 21 in an individual with Down syndrome?
A) nondisjunction in the mother only
B) nondisjunction in the father only
C) duplication of the chromosome
D) nondisjunction or translocation in either parent
E) It is impossible to detect with current technology.

Answer: D

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
A) 8%
B) 16%
C) 31%
D) 42%
E) It cannot be determined from the information provided.

Answer: A

Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?
A) the diameter of the helix
B) the rate of replication
C) the sequence of nucleotides
D) the bond angles of the subunits
E) the frequency of A vs. T nucleotides

Answer: A

In an analysis of the nucleotide composition of DNA, which of the following will be found?
A) A = C
B) A = G and C = T
C) A + C = G + T
D) G + C = T + A

Answer: C

Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
A) Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.
B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
C) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.
D) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.
E) Prokaryotes have telomeres, and eukaryotes do not.

Answer: B

Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
A) primase
B) DNA ligase
C) DNA polymerase III
D) topoisomerase
E) helicase

Answer: C

Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?
A) replication followed by mitosis
B) replication without separation
C) meiosis followed by mitosis
D) fertilization by multiple sperm
E) special association with histone proteins

Answer: B

To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
A) exonuclease, DNA polymerase III, RNA primase
B) helicase, DNA polymerase I, DNA ligase
C) DNA ligase, nuclease, helicase
D) DNA polymerase I, DNA polymerase III, DNA ligase
E) endonuclease, DNA polymerase I, DNA ligase

Answer: E

Which of the following would you expect of a eukaryote lacking telomerase?
A) a high probability of somatic cells becoming cancerous
B) production of Okazaki fragments
C) inability to repair thymine dimers
D) a reduction in chromosome length in gametes
E) high sensitivity to sunlight

Answer: D

Use the following list of choices for the following question
I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase

Which of the enzymes synthesizes short segments of RNA?
A) I
B) II
C) III
D) IV
E) V

Answer: E

Which of the following statements describes chromatin?
A) Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA.
B) Both heterochromatin and euchromatin are found in the cytoplasm.
C) Heterochromatin is highly condensed, whereas euchromatin is less compact.
D) Euchromatin is not transcribed, whereas heterochromatin is transcribed.
E) Only euchromatin is visible under the light microscope.

Answer: C

What is the function of topoisomerase?
A) relieving strain in the DNA ahead of the replication fork
B) elongating new DNA at a replication fork by adding nucleotides to the existing chain
C) adding methyl groups to bases of DNA
D) unwinding of the double helix
E) stabilizing single-stranded DNA at the replication fork

Answer: A

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
A) It synthesizes RNA nucleotides to make a primer.
B) It catalyzes the lengthening of telomeres.
C) It joins Okazaki fragments together.
D) It unwinds the parental double helix.
E) It stabilizes the unwound parental DNA.

Answer: C

Use the following list of choices for the following question
I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase

Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?
A) I
B) II
C) III
D) IV
E) V

Answer: D

Use the following list of choices for the following question

I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase

Which of the enzymes separates the DNA strands during replication?
A) I
B) II
C) III
D) IV
E) V

Answer: A

Use the following list of choices for the following question
I. helicase
II. DNA polymerase III
III. ligase
IV. DNA polymerase I
V. primase

Which of the enzymes covalently connects segments of DNA?
A) I
B) II
C) III
D) IV
E) V

Answer: C

Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?
A) double-stranded DNA, four kinds of dNTPs, primers, origins
B) topoisomerases, telomerases, polymerases
C) G-C rich regions, polymerases, chromosome nicks
D) nucleosome loosening, four dNTPs, four rNTPs
E) ligase, primers, nucleases

Answer: A