bio exam 3

The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come? A) the electron carrier, plastocyanin B) photosystem I C) water D) oxygen

C

The fastest way for organisms to adapt to a changing environment involves ________. A) mutation B) asexual reproduction C) sexual reproduction

C

The following question(s) refer to the pedigree chart in the accompanying figure for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle. What is the genotype of individual II-5? A) WW B) Ww C) ww D) WW or ww E) ww or Ww

C

The following question(s) refer to the pedigree chart in the accompanying figure for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle. What is the likelihood that the progeny of IV-3 and IV-4 will have the trait? A) 0 percent B) 25 percent C) 50 percent D) 75 percent E) 100 percent

C

A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism? A) tt B) Hh C) HhTt D) T E) HT

E

Asexual reproduction results in greater reproductive success than does sexual reproduction when ________. A) pathogens are rapidly diversifying B) a species has accumulated numerous deleterious mutations C) there is some potential for rapid overpopulation D) a species is expanding into diverse geographic settings E) a species is in stable and favorable environments

E

At which phase are centrioles beginning to move apart in animal cells? A) telophase B) anaphase C) prometaphase D) metaphase E) prophase

E

A G-protein receptor with GTP bound to it ________. A) is in its active state B) signals a protein to maintain its shape and conformation C) will use cGMP as a second messenger D) directly affects gene expression

A

A black guinea pig crossed with an albino guinea pig produced twelve black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for this genetic situation? A) Albino is recessive; black is dominant. B) Albino is dominant; black is incompletely dominant. C) Albino and black are codominant. D) Albino is recessive; black is codominant.

A

A cell in late anaphase of mitosis will have ________. A) no chromosomes in the center of the cell B) chromosomes clustered at one end of the cell C) individual chromatids beginning to separate from one another D) chromosomes clustered tightly at the center E) one large nuclear envelope

A

A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits? A) 1/2 B) 1/16 C) 1/8 D) 3/4 E) 9/16

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. 56) If the power fails and the lights go dark, CO2 levels will ________. A) rise as a result of both animal and plant respiration B) rise as a result of animal but not plant respiration C) remain balanced because plants will continue to fix CO2 in the dark D) fall because plants will increase CO2 fixation E) fall because plants will cease to respire in the dark

A

A triploid individual ________. A) is unable to undergo normal meiosis B) is unable to undergo mitosis C) produces offspring with an even number of chromosome sets (for example, tetraploid, hexaploid) D) has an additional stage in meiosis (meiosis I, meiosis II, and meiosis III)

A

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they ________. A) fix CO2 into organic acids during the night B) fix CO2 into sugars in the bundle-sheath cells C) fix CO2 into pyruvate in the mesophyll cells D) use the enzyme phosphofructokinase, which outcompetes rubisco for CO2 E) use photosystem I and photosystem II at night

A

Consider this pathway: epinephrine → G-protein-coupled receptor → G-protein → adenylyl cyclase → cAMP. The second messenger in this pathway is ________. A) cAMP B) G-protein C) GTP D) adenylyl cyclase E) G-protein-coupled receptor

A

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to ________. A) the cleavage furrow of eukaryotic animal cells B) the cell plate of eukaryotic plant cells C) the mitotic spindle of eukaryotic cells D) the microtubule-organizing center of eukaryotic cells

A

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce ________. A) all sharp-spined progeny B) 50 percent sharp-spined, 50 percent dull-spined progeny C) 25 percent sharp-spined, 50 percent dull-spined, 25 percent spineless progeny D) all spineless progeny E) It is impossible to determine the phenotypes of the progeny.

A

Genetic mutations in asexually reproducing organisms lead to more evolutionary change than do genetic mutations in sexually reproducing ones because ________. A) asexually reproducing organisms, but not sexually reproducing organisms, pass all mutations on to their offspring B) asexually reproducing organisms devote more time and energy to the process of reproduction than do sexually reproducing organisms C) sexually reproducing organisms can produce more offspring in a given time than can asexually reproducing organisms D) more genetic variation is present in organisms that reproduce asexually than is present in those that reproduce sexually E) asexually reproducing organisms have more dominant genes than organisms that reproduce sexually

A

If a cell has accumulated DNA damage, it is unlikely to ________. A) pass the G2 checkpoint B) activate DNA repair mechanisms C) enter G1 from mitosis D) synthesize cyclin-dependent kinases

A

If a cell has completed meiosis I and is just beginning meiosis II, which of the following is an appropriate description of its contents? A) It has half the amount of DNA as the cell that began meiosis. B) It has the same number of chromosomes, but each of them has different alleles than another cell from the same meiosis. C) It has half the chromosomes but twice the DNA of the originating cell. D) It has one-fourth the DNA and one-half the chromosomes as the originating cell. E) It is identical in content to another cell formed from the same meiosis I event.

A

If an organism is diploid and a certain gene found in the organism has 18 known alleles (variants), then any given organism of that species can/must have which of the following? A) at most, 2 alleles for that gene B) up to 18 chromosomes with that gene C) up to 18 genes for that trait D) a haploid number of 9 chromosomes E) up to, but not more than, 18 different traits

A

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 the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1—4 correspond to plants that will be true-breeding? A) 1 and 4 only B) 2 and 3 only C) 1, 2, 3, and 4 D) 1 only E) 1 and 2 only

A

In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and ________. A) carotenoids and other pigments are still present in the leaves B) the degraded chlorophyll changes into many other colors C) water supply to the leaves has been reduced D) sugars are sent to most of the cells of the leaves

A

In general, a signal transmitted via phosphorylation of a series of proteins ________. A) results in a conformational change to each protein B) requires binding of a hormone to an intracellular receptor C) activates a transcription event D) generates ATP in the process of signal transduction E) occurs within the outer plasma membrane

A

In humans, blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait. A woman with blue eyes and normal color vision whose father was color-blind marries a man who also has normal color vision. He has brown eyes but his mother had blue eyes. Which of the following would you expect to be TRUE for their daughters? A) One-half of their daughters will have normal color vision and brown eyes; one-half of their daughters will have normal color vision and blue eyes. B) Their daughters will all have normal color vision and brown eyes. C) One-fourth of their daughters will be color-blind and have blue eyes, one-fourth of their daughters will be color-blind and have brown eyes, one-fourth of their daughters will have normal color vision and blue eyes, and one-fourth of their daughters will have normal color vision and brown eyes. D) Their daughters will all have normal color visi

A

In plant cells, the middle lamella ________. A) allows adjacent cells to adhere to one another B) prevents dehydration of adjacent cells C) maintains the plant's circulatory system D) allows for gas and nutrient exchange among adjacent cells

A

In plants, reduction of NADP+ occurs during ________. A) photosynthesis B) respiration C) photosynthesis and respiration D) neither photosynthesis nor respiration

A

In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces black fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur? A) 25 percent B) 33 percent C) about 66 percent D) 100 percent E) 50 percent

A

In the cells of some organisms, mitosis occurs without cytokinesis. This results in ________. A) cells with more than one nucleus B) cells that are unusually small C) cells lacking nuclei D) destruction of chromosomes E) cell cycles lacking an S phase

A

In the figure, G1 is represented by which numbered part(s) of the cycle? A) I or V B) II or IV C) III only D) IV only E) V only

A

In tigers, a recessive allele causes a white tiger (absence of fur pigmentation). If one phenotypically normal tiger that is heterozygous is mated to another that is phenotypically white, what percentage of their offspring is expected to be white? A) 50 percent B) 75 percent C) 0 percent D) 100 percent E) 25 percent

A

Independent assortment of chromosomes is a result of ________. A) the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I B) the random combinations of eggs and sperm during fertilization C) the random distribution of the sister chromatids to the two daughter cells during anaphase II D) the relatively small degree of homology shared by the X and Y chromosomes E) the diverse combination of alleles that may be found within any given chromosome

A

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction? A) a lipid-soluble signal B) a signal that is weakly bound to a nucleotide C) a signal that binds to a receptor in the cell membrane D) a signal that binds to the ECM

A

Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that ________. A) gamma contains more DNA than beta B) beta and gamma contain the same amount of DNA C) beta cells reproduce asexually D) beta are in the G0 phase E) beta is a plant cell and gamma is an animal cell

A

One characteristic of life and living systems is that they are able to adapt. In general, cells interact with other cells and their environment through the action of their ________. A) plasma membrane and extracellular matrix B) microtubular tracks C) hormones D) intracellular electrical currents

A

Photorespiration ________. A) generates carbon dioxide and consumes ATP and oxygen B) generates ATP and sugars and consumes oxygen and carbon dioxide C) generates oxygen and consumes ATP, carbon dioxide, and sugars D) consumes carbon dioxide and generates ATP, sugars, and oxygen

A

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes. For this to happen there must be direct communication between the extracellular matrix and the developing cells. Which kind of transmembrane protein would most likely be involved in this kind of induction? A) integrins B) collagens C) actins D) fibronectins

A

Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH 8 solution. What would most likely happen? A) The isolated chloroplasts would make ATP. B) The Calvin cycle would be activated. C) Cyclic photophosphorylation would occur. D) The isolated chloroplasts would generate oxygen gas. E) The isolated chloroplasts would reduce NADP+ to NADPH.

A

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect ________. A) the structure of the mitotic spindle B) anaphase C) formation of the centrioles D) chromatid assembly E) the S phase of the cell cycle

A

The MPF protein complex turns itself off by ________. A) activating a process that destroys cyclin components B) activating an enzyme that stimulates cyclin C) binding to chromatin D) exiting the cell E) activating the anaphase-promoting complex

A

The activation of receptor tyrosine kinases is characterized by ________. A) dimerization and phosphorylation B) dimerization and IP3 binding C) a phosphorylation cascade D) GTP hydrolysis E) channel protein shape change

A

The cancer-causing forms of the Ras protein are involved in which of the following processes? A) relaying a signal from a growth-factor receptor B) DNA replication C) DNA repair D) cell—cell adhesion E) cell division

A

The chemiosmotic process in chloroplasts involves the ________. A) establishment of a proton gradient across the thylakoid membrane B) diffusion of electrons through the thylakoid membrane C) reduction of water to produce ATP D) movement of water by osmosis into the thylakoid space from the stroma E) formation of glucose, using carbon dioxide, NADPH, and ATP

A

The first gap in the cell cycle (G1) corresponds to ________. A) normal growth and cell function B) the phase in which DNA is being replicated C) the beginning of mitosis D) the phase between DNA replication and the M phase

A

The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find? A) The pH within the thylakoid is less than that of the stroma. B) The pH of the stroma is lower than that of the other two measurements. C) The pH of the stroma is higher than that of the thylakoid space but lower than that of the cytosol. D) The pH of the thylakoid space is higher than anywhere else in the cell. E) There is no consistent relationship.

A

The product of the p53 gene ________. A) inhibits the cell cycle B) slows down the rate of DNA replication by interfering with the binding of DNA polymerase C) causes cells to reduce expression of genes involved in DNA repair D) allows cells to pass on mutations due to DNA damage

A

The proteins of the electron transport chain active in the light-dependent reactions ________. A) are membrane proteins present in the thylakoid B) are free proteins present in the thylakoid lumen C) are considered to be part of the reaction center of photosystem I D) absorb the same wavelengths of light as their associated chlorophylls

A

Turner syndrome is characterized by the presence of only one X chromosome in an affected female. Which of the following accurately describes Turner syndrome? A) monosomy B) trisomy C) 2n + 1 D) 47,XXX aneuploidy

A

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to ________. A) disruption of mitotic spindle formation B) inhibition of regulatory protein phosphorylation C) suppression of cyclin production D) myosin denaturation and inhibition of cleavage furrow formation E) inhibition of DNA synthesis

A

What is a major difference between mitosis and meiosis I in a diploid organism? A) Sister chromatids separate in mitosis; homologous pairs of chromosomes separate in meiosis I. B) Sister chromatids separate in mitosis; homologous pairs of chromosomes separate in meiosis II. C) DNA replication takes place prior to mitosis, but not before meiosis I. D) Only meiosis I results in daughter cells that contain identical genetic information.

A

What is the most common source of the extra chromosome 21 in an individual with Down syndrome? A) nondisjunction in the mother B) nondisjunction in the father C) duplication of chromosome 21 D) deletion in either parent

A

What makes sexually reproduced offspring genetically different from their parents? A) genetic recombination during meiosis B) genetic recombination during mitosis C) crossing over during mitosis D) Sexual reproduction does not produce genetically different offspring.

A

What wavelength of light in the figure is most effective in driving photosynthesis? A) 420 mm B) 475 mm C) 575 mm D) 625 mm E) 730 mm

A

When does the synaptonemal complex disappear? A) late prophase of meiosis I B) during fertilization or fusion of gametes C) early anaphase of meiosis I D) mid-prophase of meiosis II E) late metaphase of meiosis II

A

Where do the enzymatic reactions of the Calvin cycle take place? A) stroma of the chloroplast B) thylakoid membranes C) matrix of the mitochondria D) cytosol around the chloroplast E) thylakoid space

A

Where would you expect to find tight junctions? A) in the epithelium of an animal's stomach B) between the smooth endoplasmic reticulum and the rough endoplasmic reticulum C) between plant cells in a woody plant D) in the plasma membrane of prokaryotes

A

Which component is a protein fiber of the extracellular matrix? A) A B) B C) C D) D E) E

A

Which cytoskeletal proteins are important constituents of the contractile structures that form the cleavage furrows involved in animal cell cytokinesis? A) actin B) dynein C) tubulin D) myosin

A

Which is the smallest unit containing the entire human genome? A) one male somatic cell B) one human chromosome C) all of the DNA in all of the cells of one human D) all of the DNA in all of the cells of the entire human population E) one human gamete

A

Which of the following could be considered an evolutionary advantage of asexual reproduction in plants? A) increased success of progeny in a stable environment B) increased agricultural productivity in a rapidly changing environment C) maintenance and expansion of a large genome D) production of numerous progeny E) increased ability to adapt to a change in the environment

A

Which of the following happens at the conclusion of meiosis I? A) Homologous chromosomes of a pair are separated from each other. B) The chromosome number per cell remains the same. C) Sister chromatids are separated. D) Four daughter cells are formed. E) Cohesins are cleaved at the centromeres.

A

Which of the following might result in a human zygote with 45 chromosomes? A) an error in either egg or sperm meiotic anaphase B) failure of the egg nucleus to be fertilized by the sperm C) failure of an egg to complete meiosis II D) incomplete cytokinesis during spermatogenesis after meiosis I

A

Which of the following statements about independent assortment and segregation is correct? A) The law of independent assortment requires describing two or more genes relative to one another. B) The law of segregation requires describing two or more genes relative to one another. C) The law of segregation requires having two or more generations to describe. D) The law of independent assortment is accounted for by observations of prophase I. E) The law of segregation is accounted for by anaphase of mitosis.

A

Which of the following statements about quorum sensing is FALSE? Quorum sensing ________. A) is cell—cell communication in eukaryotes B) is species specific C) may result in biofilm formation D) is particularly well studied because of its medical importance

A

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 Calvin cycle returns ADP, i, 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.

A

A triploid cell contains sets of 3 homologous chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following? A) 63 chromosomes in 31 1/2 pairs B) 63 chromosomes in 21 sets of 3 C) 63 chromosomes, each with 3 chromatids D) 21 chromosome pairs and 21 unique chromosomes

B

Acetylcholine is a neurotransmitter that binds to receptors on skeletal muscle cells. The receptor—signal complex brings about a series of events that result in contraction of skeletal muscle. Venom from black widow spiders causes an explosive release of acetylcholine. What would that do to its victims? A) The victim's muscles would be unable to contract. B) The victim's muscles would be unable to relax. C) The victim's cell receptors would no longer be able to bind regulatory hormones. D) The victim's cell receptors would be able to bind regulatory hormones but at a rate greatly exceeding normal rates.

B

Asexual reproduction occurs during ________. A) meiosis B) mitosis C) fertilization D) chromosome exchange between organisms of different species

B

BRCA1 and BRCA2 are considered to be tumor suppressor genes because ________. A) they prevent infection by tumor viruses that cause cancer B) their normal products participate in repair of DNA damage C) the mutant forms of either one of these prevent breast cancer D) the normal genes make estrogen receptors E) they block penetration of breast cells by chemical carcinogens

B

Blood sugar is regulated by two pancreatic hormones—insulin and glucagon. When blood sugar rises, insulin is released; it binds to receptors and, through signal transduction, results in an increase in glucose uptake by cells, which effectively lowers blood glucose levels. When blood sugar decreases, glucagon is released, binds to cell receptors, and causes glucose to be released into circulation, thereby increasing blood glucose levels. Diabetes mellitus is a disorder that results from excessively high levels of blood glucose. Type II diabetics have normal to elevated levels of insulin. What, then, might be causing their elevated blood glucose levels? A) inadequate insulin production B) defective receptors C) defective second messenger D) overproduction of glucagon

B

Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants? A) They serve as accessory pigments to increase light absorption. B) They protect against oxidative damage from excessive light energy. C) They shield the sensitive chromosomes of the plant from harmful ultraviolet radiation. D) They reflect orange light and enhance red light absorption by chlorophyll. E) They take up and remove toxins from the groundwater.

B

Chlorophylls absorb most light in which colors of the visible range? A) green and blue B) blue and red C) green and red D) violet and red

B

Crossing over normally takes place during which of the following processes? A) meiosis II B) meiosis I C) mitosis D) mitosis and meiosis II

B

During which phase of mitosis do the chromatids become chromosomes? A) telophase B) anaphase C) prophase D) metaphase E) cytokinesis

B

Energy from sunlight can excite electrons, kicking them out of their orbitals and creating free radicals. Free radicals are highly reactive atoms or molecules that have unpaired electrons and degrade and destroy other compounds in their vicinity. Carotenoids, one of the pigments present in most chloroplasts, can stabilize these free radicals. This suggests that ________. A) once chloroplasts are destroyed, the free radicals will destroy the cell B) carotenoids probably have a protective function in the cell C) free radicals induce the synthesis of carotenoids in chloroplasts D) carotenoids communicate directly with the immune system of plants

B

For a tissue or an organ to function as a unit, ________. A) there must be a signal molecule recognized by all cells in the tissue or organ B) there must be cell—cell communication among the cells within a tissue or organ C) the tissue or organ must perform similar functions D) the tissue or organ must be composed of all of the same type of cells

B

For the duration of meiosis I, each chromosome ________. A) is paired with a homologous chromosome B) consists of two sister chromatids joined by a centromere C) consists of a single strand of DNA D) is joined with its homologous pair to form a synaptonemal complex

B

Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white. (a) What is the most probable genotype of each parent? (b) Based on your answer in (a) above, what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols: G = gray and g = white.) A) (a) GG × gg; (b) genotypic = 3:1, phenotypic = 1:2:1 B) (a) Gg × Gg; (b) genotypic = 1:2:1, phenotypic = 3:1 C) (a) GG × Gg; (b) genotypic = 1:2:1, phenotypic = 2:1 D) (a) gg × Gg; (b) genotypic = 1:2, phenotypic = 3:1 E) (a) Gg × Gg; (b) genotypic = 3:1, phenotypic = 9:3:3:1

B

Homologous chromosomes ________. A) are identical B) carry information for the same traits C) carry the same alleles D) align on the metaphase plate in meiosis II

B

Homologous pairs of chromosomes align opposite to each other at the equator of a cell during ________. A) metaphase of mitosis B) metaphase I of meiosis C) telophase II of meiosis D) metaphase II of meiosis

B

How are the light-dependent and light-independent reactions of photosynthesis related? A) The products of light-independent reactions are used in light-dependent reactions. B) The products of light-dependent reactions are used in light-independent reactions. C) The products of light-independent reactions must be present for light-dependent reactions to take place. D) They are not related.

B

How is plant cell cytokinesis different from animal cell cytokinesis? A) The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile phospholipids. B) Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow. C) The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells. D) Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase.

B

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE? A) 4 B) 8 C) 16 D) 32 E) 64

B

If there are 20 chromatids in a cell, how many centromeres are there? A) 10 B) 20 C) 30 D) 40 E) 80

B

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white? A) red × white B) roan × roan C) white × roan D) red × roan E) The answer cannot be determined from the information provided.

B

In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit ________. A) cytokinesis B) the attachment of microtubules to kinetochores C) the splitting of the centrosomes D) the disassembly of the nucleolus

B

In its mechanism, photophosphorylation is most similar to ________. A) substrate-level phosphorylation in glycolysis B) oxidative phosphorylation in cellular respiration C) the Calvin cycle D) carbon fixation E) reduction of NADP+

B

In the figure, which number represents DNA synthesis? A) I B) II C) III D) IV E) V

B

In the figure, which number represents the point in the cell cycle during which the chromosomes are replicated? A) I B) II C) III D) IV E) V

B

In the snail Pomacea patula catemacensis, n = 13. What is the diploid number for this organism? A) 13 B) 26 C) 52 D) 7

B

Independent assortment of chromosomes occurs during ________. A) mitosis only B) meiosis I only C) meiosis II only D) mitosis and meiosis I E) mitosis and meiosis II

B

Integrins are integral membrane proteins. They are often attached to ________. A) the membranes of intracellular organelles B) cytoskeletal proteins and proteins in the extracellular matrix C) the outside of the plasma membrane D) glycogen molecules and other types of cellular inclusions

B

Intercalated discs are cell—cell junctions found between cardiac muscle cells. One feature of these intercalated discs is that they contain a large number of gap junctions, which means that ________. A) an extension of smooth endoplasmic reticulum goes through the gap junction, making it continuous from one cardiac muscle cell to the next B) water ions and small molecules can readily pass from one cardiac muscle cell to the next C) cardiac cells can function independently when necessary D) RNA from one cardiac muscle cell can be transported into an adjacent cell through the gap junction

B

Kinetochore microtubules assist in the process of splitting centromeres by ________. A) using motor proteins to split the centromere at specific arginine residues B) creating tension by pulling toward opposite poles C) sliding past each other like actin filaments D) phosphorylating the centromere, thereby changing its conformation

B

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because ________. A) only target cells retain the appropriate DNA segments B) intracellular receptors are present only in target cells C) most cells lack the Y chromosome required D) only target cells possess the cytosolic enzymes that transduce the testosterone E) only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor

B

Mitosis separates chromosomes. Cytoplasm is divided between two daughter cells by ________. A) cloning B) cytokinesis C) binary fission D) the formation of kinetochores

B

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and, therefore, can 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. 15) Which of the following questions might be answered by using the method described? 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?

B

Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are ________. A) components of the plasma membrane of osteocytes B) part of the extracellular matrix C) extensions of the endoplasmic reticulum D) deposited by the circulatory system but not associated with the osteocytes

B

Plasmodesmata are cell—cell junctions that are found between ________. A) individual cardiac cells in heart muscle tissue B) adjacent plant cells C) adjacent animal cells in the same tissue type D) the plasma membrane of actively dividing prokaryotes

B

Reactions that require CO2 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 not as part of photosynthesis

B

Refer to the figure. If the carbon atom of each of the incoming CO2 molecules is labeled with a radioactive isotope of carbon, which organic molecules will be radioactively labeled after one cycle? A) C only B) B, C, D, and E C) C, D, and E only D) B and C only E) B and D only

B

Sexual reproduction ________. A) allows animals to conserve resources and reproduce only during optimal conditions B) can produce diverse phenotypes that may enhance survival of a population in a changing environment C) yields more numerous offspring more rapidly than is possible with asexual reproduction D) enables males and females to remain isolated from each other while rapidly colonizing habitats E) guarantees that both parents will provide care for each offspring

B

Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm? A) four B) two C) eight D) a diploid number

B

Some photosynthetic organisms contain chloroplasts that lack photosystem II yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be to ________. A) determine if they have thylakoids in the chloroplasts B) test for liberation of O2 in the light C) test for CO2 fixation in the dark D) do experiments to generate an action spectrum E) test for production of either sucrose or starch

B

Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are 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

B

The light-independent reactions of plants function to make organic molecules using carbon dioxide as a carbon source. What is the electron source that helps reduce carbon dioxide to sugars and other organic molecules? A) NADH B) NADPH C) ATP D) electrons from oxygen

B

The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as the ________. A) microtubulere B) centrosome C) centromere D) kinetochore

B

The process of photosynthesis probably originated ________. A) in plants B) in prokaryotes C) in fungi D) three separate times during evolution

B

The work of Gregor Mendel provided an answer to two prevailing hypotheses popular at the time. What were these two hypotheses? A) Mitosis is only typical in vertebrates. Meiosis is only typical in invertebrates. B) The two major hypotheses of the time were blending inheritance and inheritance of acquired characteristics. C) Animals use one set of rules for inheritance, and plants use a different set. D) Peas and other domestic plants are unsuited for studies of inheritance, but wild plants are perfectly suited. E) Self-fertilization is the rule in plants, whereas cross-fertilization is the rule in animals.

B

Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light. If you ran the same experiment as Engelmann without passing light through a prism, what would you predict? A) The results would be the same. B) The bacteria would be relatively evenly distributed along the algal filaments. C) The number of bacteria present would decrease due to an increase in the carbon dioxide concentration. D) The number of bacteria present would increase due to an increase in the carbon dioxide concentration. E) The number of bacteria would decrease due to a decrease in the temperature of the water.

B

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely ________. A) an animal cell in the process of cytokinesis B) a plant cell in the process of cytokinesis C) an animal cell in the S phase of the cell cycle D) a bacterial cell dividing E) a plant cell in metaphase

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. If 1000 F2 offspring resulted from a dihybrid cross, approximately how many of them would you expect to have red, terminal flowers? A) 65 B) 190 C) 250 D) 565 E) 750

B

What does it mean to say that a signal is transduced? A) The signal enters the cell directly and binds to a receptor inside. B) The physical form of the signal changes from one form to another. C) The signal is amplified, such that even a single molecule evokes a large response. D) The signal triggers a sequence of phosphorylation events inside the cell.

B

What is a major difference between the extracellular matrix (ECM) of a plant cell and the ECM of an animal cell? A) Plant ECM is composed primarily of proteins, whereas animal ECM is mainly carbohydrates. B) Plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins. C) Plant and animal ECMs are quite similar in structure and function. D) ECM components in plant cells are released extracellularly by the Golgi stacks, whereas lysosomes do this in animal cells.

B

What is the correct chromosomal condition at prometaphase of mitosis? A) A B) B C) C D) D E) E

B

What would be the expected effect on plants if the atmospheric CO2 concentration was doubled? A) All plants would experience increased rates of photosynthesis. B) C3 plants would have faster growth; C4 plants would be minimally affected. C) C4 plants would have faster growth; C3 plants would be minimally affected. D) C3 plants would have faster growth; C4 plants would have slower growth. E) Plant growth would not be affected because atmospheric CO2 concentrations are never limiting for plant growth.

B

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white- eyed flies were male. What was the explanation for this result? A) The gene involved is on the Y chromosome. B) The gene involved is on the X chromosome. C) The gene involved is on an autosome, but only in males. D) Other male-specific factors influence eye color in flies. E) Other female-specific factors influence eye color in flies.

B

When does DNA replication take place regarding meiosis? DNA replication ________. A) does not take place in cells destined to undergo meiosis B) occurs before meiosis I begins C) occurs between meiosis I and meiosis II D) occurs during prophase I

B

When oxygen is released as a result of photosynthesis, it is a direct by-product of ________. A) reducing NADP+ B) splitting water molecules C) chemiosmosis D) the electron transfer system of photosystem I E) the electron transfer system of photosystem II

B

When yeast cells of opposite mating types are in close proximity, cell changes occur inside those cells that result in the polymerization of actin filaments, allowing the yeast cells to mate. Those changes in cell behavior are initially due to signaling molecules (pheromones) released by the yeast cells. Pheromones are ________. A) a type of steroid hormone that diffuses through the plasma membrane causing cytoplasmic actin proteins to form filaments B) a type of hormone that binds cell-surface receptors causing cytoplasmic actin proteins to form filaments C) signaling molecules that bind cell-surface receptors causing yeast cells to become motile, insuring mating success D) signaling molecules that cause the extracellular matrix of yeast cells to thicken in preparation for cell fusion E) signaling molecules that cause intracellular G-proteins to be inhibited

B

Which of the following are directly associated with photosystem I? A) harvesting of light energy by ATP B) receiving electrons from the thylakoid membrane electron transport chain C) generation of molecular oxygen D) extraction of hydrogen electrons from the splitting of water E) passing electrons to the cytochrome complex

B

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells? A) kinetochores B) Golgi-derived vesicles C) actin and myosin D) centrioles and centromeres E) tubulin and dynein

B

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

B

Which of the following is a TRUE statement about sexual versus asexual reproduction? A) Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi. B) In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring. C) In asexual reproduction, offspring are produced by fertilization without meiosis. D) Sexual reproduction requires that parents be diploid. E) Asexual reproduction produces only haploid offspring.

B

Which of the following is the meaning of the chromosome theory of inheritance as expressed in the early twentieth 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.

B

Which of the following occurs in meiosis but not in mitosis? A) chromosome replication B) synapsis of chromosomes C) production of daughter cells D) alignment of chromosomes at the equator E) condensation of chromosomes

B

Which of the following sequences correctly represents the flow of electrons during photosynthesis? A) NADPH → O2 → CO2 B) H2O → NADPH → Calvin cycle C) NADPH → chlorophyll → Calvin cycle D) H2O → photosystem I → photosystem II E) NADPH → electron transport chain → O2

B

Which of the following statements best describes the relationship between photosynthesis and respiration? A) Respiration runs the biochemical pathways of photosynthesis in reverse. B) Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules C) Photosynthesis occurs only in plants; respiration occurs only in animals. D) ATP molecules are produced in photosynthesis but not in aerobic respiration. E) Photosynthesis is catabolic; respiration is anabolic.

B

Which of the following would enable you to detect aneuploidy? A) autosomy B) karyotyping C) syngamy D) synapsis

B

Why are there several structurally different pigments in the reaction centers of photosystems? A) Excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain. B) This arrangement enables the plant to absorb light energy of a variety of wavelengths. C) They enable the plant to absorb more photons from light energy, all of which are at the same wavelength. D) They enable the reaction center to excite electrons to a higher energy level.

B

The decline of MPF activity at the end of mitosis is due to ________. A) the destruction of the protein kinase Cdk B) decreased synthesis of Cdk C) the degradation of cyclin D) the accumulation of cyclin E) synthesis of DNA

C

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure. If a female of this species has one chromosome 12 with a blue gene and another chromosome 12 with an orange gene, and has both number 19 chromosomes with short genes, she will produce which of the following egg types? A) only blue short gene eggs B) only orange short gene eggs C) one-half blue short and one-half orange short gene eggs D) three-fourths blue long and one-fourth orange short gene eggs E) three-fourths blue short and one-fourth orange short gene eggs

C

The diploid number of a roundworm species is 4. Assuming there is no crossover, and random segregation of homologs during meiosis, how many different possible combinations of chromosomes might there be in the offspring? A) 4 B) 8 C) 16 D) 64

C

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

C

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation and have one child out of three who is albino (without melanin pigmentation). What are the genotypes of the albino's parents? A) One parent must be homozygous for the recessive allele; the other parent can be homozygous dominant, homozygous recessive, or heterozygous. B) One parent must be heterozygous; the other parent can be homozygous dominant, homozygous recessive, or heterozygous. C) Both parents must be heterozygous. D) One parent must be homozygous dominant; the other parent must be heterozygous. E) Both parents must be homozygous dominant.

C

All individuals of a particular species of whiptail lizards are females. Their reproductive efforts depend on ________. A) fertilization of their eggs by males of other lizard species B) gonadal structures that only undergo mitosis C) meiosis followed by a doubling of the chromosomes in eggs D) budding prior to the development of a sexual phenotype E) fragmentation via autolysis

C

All of the following proteins may be found in the extracellular matrix of animal cells EXCEPT ________. A) collagen B) fibronectin C) actin D) All of the listed proteins are found in the extracellular matrix of animal cells.

C

An advantage of asexual reproduction is that it ________. A) allows the species to endure long periods of unstable environmental conditions B) enhances genetic variability in the species C) enables the species to rapidly colonize habitats that are favorable to that species D) produces offspring that respond effectively to new pathogens E) allows a species to easily rid itself of harmful mutations

C

As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. Where did the extra ATP molecules come from? A) photosystem II B) photosystem I C) cyclic electron flow D) linear electron flow E) chlorophyll

C

As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy? A) It excites electrons of the reaction center of photosystem I. B) It is lost as heat. C) It is used to establish and maintain a proton gradient. D) It is used to phosphorylate NAD+ to NADPH, the molecule that accepts electrons from photosystem I.

C

Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring? A) 1/2 B) 1/16 C) 1/8 D) 3/4 E) 9/16

C

Centromeres split and sister chromatids migrate to opposite poles in ________ of meiosis. A) anaphase I B) telophase I C) anaphase II D) telophase II

C

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

C

Different body cells can respond differently to the same peptide hormones because ________. A) different target cells have different sets of genes B) each cell converts that hormone to a different metabolite C) a target cell's response is determined by the components of its signal transduction pathways D) the circulatory system regulates responses to hormones by routing the hormones to specific targets E) the hormone is chemically altered in different ways as it travels through the circulatory system

C

Different ratios occur in crosses with single gene pairs or two gene pairs. What types of ratios are likely to occur in crosses dealing with a single gene pair? A) 9:3:3:1, 1:2:1 B) 1:1:1:1, 1:4:6:4:1 C) 3:1, 1:1, 1:2:1 D) 4:1, 1:1, 1:4:1

C

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of 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 twenties. How likely is it for a woman to have this condition? A) Women can never have this condition. B) One-fourth of the daughters of an affected man would have this condition. C) One-half of the daughters of an affected father and a carrier mother could have this condition. D) Only if a woman is XXX could she have this condition.

C

Exposure of zebrafish nuclei to meiotic cytosol resulted in phosphorylation of NEP55 and L68 proteins by cyclin-dependent kinase 2. NEP55 is a protein of the inner nuclear membrane, and L68 is a protein of the nuclear lamina. What is the most likely role of phosphorylation of these proteins in the process of mitosis? A) They enable the attachment of the spindle microtubules to kinetochore regions of the centromere. B) They are involved in the disassembly and dispersal of the nucleolus. C) They are involved in the disassembly of the nuclear envelope. D) They assist in the movement of the centrosomes to opposite sides of the nucleus.

C

Given the parents AABBCc × AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent with genotype AABBCc? A) 1/4 B) 1/8 C) 3/4 D) 3/8 E) 1

C

H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted the cell—cell interaction (cell junctions), and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How do you explain the results of Wilson's experiments? A) The two species of sponge had different enzymes that functioned in the reassembly process. B) The molecules responsible for cell—cell adhesion (cell junctions) were irreversibly destroyed during the experiment. C) The molecules responsible for cell—cell adhesion (cell junctions) differed

C

Hexaploid wheat was produced synthetically by He and co-workers. They mated the diploid species, A. tauschii, and the tetraploid species, T. turgidum. Which of the following is an accurate statement about the relative contribution of each parent to the genome of the hexaploid offspring? A) Each parent contributed equally to the genome of the offspring. B) Aegilops tauschii contributed four chromosomes by failing to complete meiosis after chromosome replication, and T. turgidum contributed two chromosomes. C) Aegilops tauschii contributed two sets of chromosomes, and T. turgidum contributed four sets of chromosomes. D) The hexaploid number appeared following mitosis with no subsequent cell division.

C

Hutchinson—Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of 13 years. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption? A) The disease is autosomal dominant. B) The disorder will increase in frequency in successive generations within a family. C) The disorder may be due to mutation in a single protein-coding gene. D) Each patient will have had at least one affected grandparent or parent.

C

If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants? A) backtracking through her previous experiments to obtain another plant with the same traits B) breeding this plant with another plant with much weaker traits C) cloning the plant D) forcing the plant to self-pollinate to obtain an identical one E) adding nitrogen to the soil of the offspring of this plant so the desired traits continue

C

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) They have nothing in common except that they are X-shaped.

C

In eukaryotic cells, chromosomes are composed of ________. A) DNA and RNA B) DNA only C) DNA and proteins D) DNA and phospholipids

C

In humans, blue eyes are inherited as a recessive autosomal trait and color blindness is an X-linked recessive trait. A woman with blue eyes and normal color vision whose father was color-blind marries a man who also has normal color vision. He has brown eyes, but his mother had blue eyes. Which of the following would you expect to be TRUE for their sons? A) One-half of their sons will have normal color vision and brown eyes; one-half of their sons will have normal color vision and blue eyes. B) Their sons will all have normal color vision and brown eyes. C) One-fourth of their sons will be color-blind and have blue eyes, one-fourth of their sons will be color-blind and have brown eyes, one-fourth of their sons will have normal color vision and blue eyes, one-fourth of their sons will have normal color vision and brown eyes. D) Their sons will all have normal color vision and blue eyes. E) One-half of their sons will

C

In mitochondria, chemiosmosis moves protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis moves protons from the ________. A) stroma to photosystem II B) matrix to the stroma C) stroma to the thylakoid space D) intermembrane space to the matrix E) thylakoid space to the stroma

C

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

C

In the accompanying figure, MPF reaches its highest concentration during this stage. A) I B) II C) III D) IV E) V

C

In the figure, at which of the numbered regions would you expect to find cells at metaphase? A) I and IV B) II only C) III only D) IV only E) V only

C

Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that ________. A) new mutations were frequently generated in the F2 progeny, "reinventing" traits that had been lost in the F1 B) the mechanism controlling the appearance of traits was different between the F1 and the F2 plants C) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1 generation D) members of the F1 generation had only one allele for each trait, but members of the F2 had two alleles for each trait

C

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6022 yellow and 2001 green (8023 total). The allele for green seeds has what relationship to the allele for yellow seeds? A) dominant B) incomplete dominant C) recessive D) codominant

C

Mendel studies seven different traits in the garden pea. What genetic term is used to describe an observable trait, such as those studied by Mendel? A) genotype B) appearance C) phenotype D) haplotype E) category

C

Myosin is a motor protein involved in animal cell cytokinesis. It binds to ATP or ADP, causing the myosin to move with respect to actin. What is the effect of the interaction between myosin and actin? A) Vesicles containing plasma membrane constituents are transported to the metaphase plate, where cytokinesis takes place. B) Excess cytoplasm is removed. C) The cleavage furrow deepens. D) Two new daughter nuclei form.

C

Neurons and some other specialized cells divide infrequently because they ________. A) no longer have active nuclei B) no longer carry receptors for signal molecules C) have entered into G0 D) can no longer bind Cdk to cyclin E) show a drop in MPF concentration

C

The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why? A) Each one minimizes both water loss and rate of photosynthesis. B) C4 compromises on water loss and CAM compromises on photorespiration. C) Both minimize photorespiration but expend more ATP during carbon fixation. D) CAM plants allow more water loss, and C4 plants allow less CO2 into the plant. E) C4 plants allow less water loss, but CAM plants allow more water loss.

C

The egg of a fruit fly has 4 individual chromosomes. How many chromosomes are in a somatic cell of a fruit fly? A) 4 B) 2 C) 8 D) 16

C

Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and, therefore, can 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 their experiments 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 experiments 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 ski

C

Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis? A) It is completely degraded. B) It is exported from the cell. C) The cyclin component of MPF is degraded. D) The Cdk component of MPF is degraded and exported from the cell.

C

Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize the amino acid phenylalanine. This amino acid is not naturally produced by humans. Therefore, the most efficient and effective treatment is which of the following? A) Feed them the substrate that can be metabolized into this amino acid. B) Transfuse the patients with blood from unaffected donors. C) Regulate the diet of the affected persons to severely limit the uptake of the amino acid. D) Feed the patients the missing enzymes in a regular cycle, such as twice per week. E) Feed the patients an excess of the missing product.

C

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________. A) are species specific B) always lead to the same cellular response C) amplify the original signal many times D) counter the harmful effects of phosphatases E) use a small and fixed number of molecules

C

Plants photosynthesize ________. A) only in the light but respire only in the dark B) only in the dark but respire only in the light C) only in the light but respire in light and dark rD) and respire only in the light E) and respire only in the dark

C

Plants produce more seeds when they reproduce asexually than sexually. Yet most plants reproduce sexually in nature. What is the probable explanation for the prevalence of sexual reproduction? Sexual reproduction ________. A) is more energy efficient than asexual reproduction B) ensures genetic continuity from parents to offspring C) mixes up alleles, contributing to variation in a species D) is not dependent on other agents of pollination

C

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

C

Protein kinase is an enzyme that ________. A) functions as a second messenger molecule B) serves as a receptor for various signal molecules C) activates or inactivates other proteins by adding a phosphate group to them D) produces second messenger molecules

C

Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal—receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released. A) 1, 2, 3, 4, 5 B) 3, 1, 2, 4, 5 C) 3, 1, 5, 2, 4 D) 1, 2, 5, 3, 4

C

Refer to the figure. To identify the molecule that accepts CO2, Calvin and Benson manipulated the carbon-fixation cycle by either cutting off CO2 or cutting off light from cultures of photosynthetic algae. They then measured the concentrations of various metabolites immediately following the manipulation. How would these experiments help identify the CO2 acceptor? A) The CO2 acceptor concentration would decrease when either the CO2 or light is cut off. B) The CO2 acceptor concentration would increase when either the CO2 or light is cut off. C) The CO2 acceptor concentration would increase when the CO2 is cut off but decrease when the light is cut off. D) The CO2 acceptor concentration would decrease when the CO2 is cut off but increase when the light is cut off. E) The CO2 acceptor concentration would stay the same regardless of the CO2 or light.

C

Scaffolding proteins are ________. A) ladderlike proteins that allow receptor—ligand complexes to climb through cells from one position to another B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores C) large molecules to which several relay proteins attach to facilitate cascade effects D) relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing E) proteins that can reach into the nucleus of a cell to affect transcription

C

Signals from the extracellular matrix to the cytoskeleton may be transmitted by ________. A) fibronectin B) proteoglycans C) integrins D) collagen E) middle lamella

C

Some cells have several nuclei per cell. How could such multinucleated cells be explained? A) The cell underwent repeated cytokinesis but no mitosis. B) The cell underwent repeated mitosis with simultaneous cytokinesis. C) The cell underwent repeated mitosis, but cytokinesis did not occur. D) The cell had multiple S phases before it entered mitosis.

C

Steroid hormones bind to receptors inside the cell and alter their conformation. The hormone—receptor complex is then transported into the nucleus, where it can directly affect gene expression. To get from the location where the receptor binds the hormone to its site of action, the hormone—receptor complex must ________. A) undergo another conformational change B) become water soluble by binding to a carrier molecule C) be transported through the nuclear pore complex D) enter the smooth endoplasmic reticulum

C

The accumulation of free oxygen in Earth's atmosphere began with the origin of ________. A) life and respiratory metabolism B) photosynthetic bacteria that had photosystem I C) cyanobacteria using photosystem II D) chloroplasts in photosynthetic eukaryotic algae E) land plants

C

The bulldog ant has a diploid number of two chromosomes. Therefore, following meiosis, each daughter cell will have a single chromosome. Diversity in this species may be generated by mutations and ________. A) crossing over B) independent assortment C) crossing over and independent assortment D) nothing else

C

The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is NOT a problem for steroids because ________. A) the receptors can be readily stimulated to exit and relocate on the membrane surface B) steroids do not directly affect cells but instead alter the chemistry of blood plasma C) steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane D) steroids must first bond to a steroid activator, forming a complex that then binds to the cell surface

C

The somatic cells of a privet shrub each contain 46 chromosomes. How do privet chromosomes differ from the chromosomes of humans, who also have 46? A) Privet cells cannot reproduce sexually. B) Privet sex cells have chromosomes that can synapse with human chromosomes in the laboratory. C) Genes of privet chromosomes are significantly different from those in humans. D) Privet shrubs must be metabolically more like animals than like other shrubs. E) Genes on a particular privet chromosome, such as the X, must be on a different human chromosome, such as number 18.

C

Tumor suppressor genes ________. A) are frequently overexpressed in cancerous cells B) are cancer-causing genes introduced into cells by viruses C) encode proteins that help prevent uncontrolled cell growth D) often encode proteins that stimulate the cell cycle

C

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 of a dihybrid cross, 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

C

Use the following information to answer the question below. Trichoplax adhaerens (Tp) is the only living species in the phylum Placozoa. Individuals are about 1 mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about 2000 cells, which are diploid (2n = 12). There are four types of cells, none of which are nerve or muscle cells, and none of which have cell walls. They move using cilia, and any "edge" can lead. Tp feeds on marine microbes, mostly unicellular green algae, by crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted onto the algae, and the resulting nutrients are absorbed. Tp sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage. If Tp sperm are observed by future researchers, how many chromosomes should be found in a Tp sperm nucleus? A) 2 B) 3 C) 6 D) 12

C

What do we mean when we use the terms "monohybrid cross" and "dihybrid cross"? A) A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents. B) A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny. C) A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied. D) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. E) A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio.

C

What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2? A) Nothing happens. B) The cells undergo meiosis. C) The cells enter mitosis. D) Cell differentiation is triggered.

C

What is a major difference between meiosis II and mitosis in a diploid animal? A) Homologs align on the metaphase plate in meiosis II B) Sister chromatids separate in mitosis, and homologs separate in meiosis II C) Meiosis II occurs in a haploid cell, and mitosis occurs in diploid cells D) Crossover takes place in meiosis II

C

What is the difference between NAD+ and NADP? A) NAD+ functions as an electron transporter, whereas NADP does not. B) NAD+ functions as a free-energy source for cells, whereas NADP does not. C) Both function as electron carriers, but NADP has a phosphate group and NAD+ does not. D) Both transport electrons to the electron transport chain (ETC) found on the inner mitochondrial membrane, but NADP transfers its electrons to the ETC at a higher energy level.

C

What is the main purpose of light-dependent reactions of photosynthesis? A) to generate oxygen by "splitting" H2O B) to produce NADPH for use in respiration C) to produce NADPH and ATP D) to use ATP to make glucose

C

What phase of meiosis is seen in the accompanying figure? A) metaphase I B) metaphase II C) anaphase I D) anaphase II

C

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 percent B) 25 percent C) 50 percent D) 75 percent E) 100 percent

C

Whether during mitosis or meiosis, sister chromatids are held together by proteins referred to as cohesins. Such molecules must ________. A) persist throughout the cell cycle B) be removed before meiosis can begin C) be removed before sister chromatids can separate D) reattach to chromosomes during G1 E) be intact for nuclear envelope re-formation

C

Which observation suggested the involvement of a second messenger in epinephrine's effect on liver cells? A) Enzymatic activity was proportional to the amount of calcium added to a cell-free extract. B) Receptor studies indicated that epinephrine was a ligand. C) Glycogen breakdown was observed only when epinephrine was administered to intact cells. D) Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined. E) Epinephrine was known to have different effects on different types of cells.

C

Which of the following can occur by the process of meiosis but not mitosis? A) Haploid cells fuse to form diploid cells. B) Haploid cells multiply into more haploid cells. C) Diploid cells form haploid cells. D) A diploid cell combines with a haploid cell.

C

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

C

Which of the following is characteristic of a steroid hormone action? A) protein phosphorylation B) cell-surface receptor binding C) internal receptor binding D) second messenger activation

C

Which of the following procedures would identify the enzyme that catalyzes the carboxylation of ribulose-1,5-bisphosphate? A) irradiating a leaf extract with red light B) introducing radiolabeled carbon dioxide into a plant extract and determining which molecules become radiolabeled C) purifying a variety of proteins from plant extracts and testing each protein individually to see if it can carboxylate ribulose-1,5-bisphosphate D) differential sedimentation of a protein extract

C

Which of the following statements is FALSE? A) When plant cells are growing, they release expansins, which are enzymes that can expand the primary cell wall. B) The secondary cell wall often contains structural components, like lignin, that form a relatively rigid and complex network within the cell wall. C) A plant cell continues growing after the secondary cell wall forms but stops growing with the formation of the tertiary cell wall. D) Pectin is a component of the cell wall that attracts and holds water.

C

Which of the following would you NOT find in a plant cell? A) pectin B) polysaccharides C) collagen D) lignin

C

A cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone's ________. A) secretory cell B) plasma cell C) endocrine cell D) target cell E) regulatory cell

D

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure. A certain female's number 12 chromosomes both have the blue gene and number 19 chromosomes both have the long gene. As cells in her ovaries undergo meiosis, her resulting eggs (ova) may have which of the following? A) either two number 12 chromosomes with blue genes or two with orange genes B) either two number 19 chromosomes with long genes or two with short genes C) either one blue or one orange gene in addition to either one long or one short gene D) one chromosome 12 with one blue gene and one chromosome 19 with one long gene

D

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure. A female with a paternal set of one orange and one long gene chromosome and a maternal set comprised of one blue and one short gene chromosome is expected to produce which of the following types of eggs after meiosis? A) All eggs will have maternal types of gene combinations. B) All eggs will have paternal types of gene combinations. C) Half the eggs will have maternal and half will have paternal combinations. D) Each egg has a one-fourth chance of having either blue long, blue short, orange long, or orange short combinations. E) Each egg has a three-fourths chance of having blue long, one-fourth blue short, three-fourths orange long, or one-fourth orange short combinations.

D

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition? A) The woman inherited this tendency from her parents. B) The mother had a chromosomal duplication. C) One member of the couple underwent nondisjunction in somatic cell production. D) The mother most likely underwent nondisjunction during gamete production.

D

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

D

A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask. The dissolved oxygen in the flask with algae will ________. A) always be higher B) always be lower C) be higher in the light but the same in the dark D) be higher in the light but lower in the dark E) not be different from the control flask at any time

D

A gap junction is a channel that connects adjacent cells. Which one of the following cannot pass through a gap junction? A) ions that can regulate heartbeat B) amino acids C) nucleotides D) ribosomes

D

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2? A) 8; 8 B) 8; 16 C) 16; 8 D) 16; 16 E) 12; 16

D

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA? A) G0 B) G1 C) S D) G2 E) M

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

D

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

D

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first child will be an albino? A) 0 B) 1/8 C) 1/2 D) 1/4 E) 1/3

D

Albinism is an autosomal (not sex-linked) recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first female child will have albinism? A) 0 B) 1/8 C) 1/2 D) 1/4 E) 1/3

D

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

D

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects? A) Estrogen is produced in very large concentration by nearly every tissue of the body. B) Each cell responds in the same way when steroids bind to the cell surface. C) Estrogen is kept away from the surface of any cells not able to bind it at the surface. D) Estrogen binds to specific receptors inside many kinds of cells, each with different responses. E) Cells metabolize steroids in different ways, producing by-products that stimulate tRNA production.

D

Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white. A blue budgie is crossed with a white budgie. Which of the following results is NOT possible? A) green offspring only B) yellow offspring only C) blue offspring only D) green and yellow offspring E) a 9:3:3:1 ratio

D

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes? A) 23 B) 46 C) about 1000 D) about 8 million E) about 70 trillion

D

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must ________. A) modify its plasma membrane to alter the hormone entering the cytoplasm B) be from the same cell type as the organ that produced the hormone C) experience an imbalance that disrupts its normal function D) have receptors that recognize and bind the hormone molecule

D

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have ________. A) twice the amount of cytoplasm and half the amount of DNA. B) half the number of chromosomes and half the amount of DNA. C) the same number of chromosomes and half the amount of DNA. D) half the number of chromosomes and one-fourth the amount of DNA. E) half the amount of cytoplasm and twice the amount of DNA.

D

How many different combinations of maternal and paternal chromosomes can be packaged in gametes made by an organism with a diploid number of 8 (2n = 8)? A) 2 B) 4 C) 8 D) 16 E) 32

D

If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state? A) DNA replication B) reverse transcription C) synapsis D) fertilization

D

If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next? A) cell-membrane synthesis B) spindle fiber formation C) nuclear envelope breakdown D) formation of telophase nuclei E) synthesis of chromatids

D

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 the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1—4 correspond to plants with a heterozygous genotype? A) 1 B) 1 and 2 C) 1, 2, and 3 D) 2 and 3 E) 2, 3, and 4

D

In a plant cell, where are the ATP synthase complexes located? A) thylakoid membrane only B) plasma membrane only C) inner mitochondrial membrane only D) thylakoid membrane and inner mitochondrial membrane E) thylakoid membrane and plasma membrane

D

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male? A) tortoiseshell females; tortoiseshell males B) black females; orange males C) orange females; orange males D) tortoiseshell females; black males E) orange females; black males

D

In meiosis, homologous chromosomes are separated during ________. A) anaphase II B) prophase I C) mitosis D) anaphase I

D

In the figure, mitosis is represented by which numbered part(s) of the cycle? A) I B) II C) III D) IV E) V

D

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division? A) prophase I of meiosis B) anaphase II of meiosis C) metaphase II of meiosis D) anaphase I of meiosis E) anaphase of mitosis

D

Movement of the chromosomes during anaphase would be most affected by a drug that prevents ________. A) nuclear envelope breakdown B) cell-wall formation C) elongation of microtubules D) shortening of microtubules E) formation of a cleavage furrow

D

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this? A) G-protein—coupled receptors B) ligand-gated ion channels C) steroid receptors D) receptor tyrosine kinases

D

P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary? A) It is the receptor for the most excited electron in either photosystem of photosynthesis. B) It is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system. C) It transfers its electrons to reduce NADP+ to NADPH. D) It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has. E) It obtains carbon from a sugar molecule, so it must have a stronger attraction for electrons than either oxygen or hydrogen.

D

Pemphigus vulgaris is an autoimmune disorder in humans in which antibodies are produced against the cadherins of desmosomes. The blistering of the skin and mucous membranes characteristic of this disorder is probably a result of ________. A) a decrease in flexibility of the cell membrane B) an inadequate number of G-protein receptors C) inadequate production of cytoskeletal proteins D) a loss in cell—cell adhesion

D

Plastoquinone (PQ), an electron carrier of small molecular weight, is found in the electron transport chain associated with photosystem II. If PQ is not directly anchored to other membrane or cytoplasmic structures, it is probably ________. A) mobile in the thylakoid membrane B) lipid soluble C) a molecule that serves as a shuttle between the electron transport chain and ATP synthase D) both lipid soluble and a molecule that serves as a shuttle between the electron transport chain and ATP synthase

D

Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems? A) 9 B) 10 C) 19 D) 38

D

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The flower color trait in radishes is an example of which of the following? A) a multiple allelic system B) sex linkage C) codominance D) incomplete dominance

D

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be expected to be which of the following? A) red and long B) red and oval C) white and long D) purple and long E) purple and oval

D

Regulatory proteins that prevent a cell from entering the S phase under conditions of DNA damage are also known as ________. A) cyclins B) cyclin-dependent kinases C) antibodies D) tumor suppressors

D

Researchers pulsed rapidly dividing cultured cells with radioactive thymidine for 30 minutes. The cells were then exposed to a solution containing non-radiolabeled thymidine. Cells were analyzed at 2-hour intervals. At the 2-hour time point, no cells appeared to be dividing. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way: A) Radiolabeled compounds are somewhat cytotoxic, and cell division was initially inhibited. B) The cells were arrested in a nondividing state because of the treatment and could not enter M phase until several hours after the label was removed. C) The synthesis (S) phase is lengthy, about 12 hours in most cell types, and the radioactive thymidine was not present long enough for most cells to be labeled. D) There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.

D

Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1 1/2 times more DNA than G1 phase cells. The cells of this group are ________. A) between the G1 and S phases in the cell cycle B) in the G2 phase of the cell cycle C) in the M phase of the cell cycle D) in the S phase of the cell cycle

D

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells? A) 4 B) 8 C) 16 D) 32 E) 64

D

Suppose two AaBbCc individuals are mated. Assuming that the genes are NOT linked, what fraction of the offspring are expected to be homozygous recessive for the three traits? A) 1/4 B) 1/8 C) 1/16 D) 1/64 E) 1/256

D

The M-phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does NOT happen, cells would most likely be arrested in ________. A) telophase B) prophase C) prometaphase D) metaphase

D

The accompanying figure shows the pedigree for a family. Dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis. Males are represented by squares, females by circles. From this pedigree, this trait seems to be inherited ________. A) from mothers B) as an autosomal recessive C) as a result of epistasis D) as an autosomal dominant E) as an incomplete dominant

D

The best conclusion concerning delta is that the cells ________. A) contain no DNA B) contain no RNA C) contain only one chromosome that is very short D) are in the G0 phase E) divide in the G1 phase

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 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 nucleotides.

D

The chromosome number of hexaploid wheat, Triticum aestivum, can be represented as ________. A) n B) 2n C) 4n D) 6n

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

D

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following? A) None of the traits obeyed the law of segregation. B) The diploid number of chromosomes in the pea plants was 7. C) All of the genes controlling the traits were located on the same chromosome. D) All of the genes controlling the traits behaved as if they were on different chromosomes. E) The formation of gametes in plants occurs by mitosis only.

D

The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different? A) Green and yellow wavelengths inhibit the absorption of red and blue wavelengths. B) Bright sunlight destroys photosynthetic pigments. C) Oxygen given off during photosynthesis interferes with the absorption of light. D) Other pigments absorb light in addition to chlorophyll a. E) Aerobic bacteria take up oxygen, which changes the measurement of the rate of photosynthesis.

D

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason? A) segregation of maternal and paternal alleles B) recurrent mutations forming new alleles C) crossing over during prophase I D) different possible assortment of chromosomes into gametes E) the tendency for dominant alleles to segregate together

D

The mitotic spindle is a microtubular structure that is involved in ________. A) splitting of the cell (cytokinesis) following mitosis B) triggering the compaction and condensation of chromosomes C) dissolving the nuclear membrane D) separation of sister chromatids

D

The phylogenetic distribution of the enzyme rubisco is limited to ________. A) only C3 plants B) C3 and C4 plants C) photosynthetic eukaryotes D) bacterial and eukaryotic photoautotrophs E) all living cells

D

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that ________. A) the parents were true-breeding for contrasting traits B) the particular trait shows incomplete dominance C) a blending of traits has occurred D) the parents were both heterozygous for the particular trait E) each offspring has the same alleles for each of two different traits

D

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)? A) ATP is synthesized from the energy absorbed. B) A carboxylation reaction of the Calvin cycle occurs. C) Electrons are stripped from NADPH. D) An electron is excited.

D

When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded plants, what genotypic ratio was expected? A) 1:2:1 B) 3:1 C) 9:3:3:1 D) 1:1 E) 1:1:1:1

D

When we first see chiasmata under a microscope, we know that ________. A) asexual reproduction has occurred B) meiosis II has occurred C) anaphase II has occurred D) prophase I is occurring E) separation of homologs has occurred

D

When yeast cells of the "a" mating type are exposed to a solution of "α" pheromones ________. A) those yeast cells will undergo cell division B) actin filaments will form a cleavage furrow in the yeast cells C) the yeast cells will fuse with each other D) G-proteins will be activated in the cell-signaling pathway and the yeast cells will change shape E) those yeast cells will undergo DNA replication

D

Which of the following is a difference between chlorophyll a and chlorophyll b? A) Chlorophyll a is a pigment, and chlorophyll b is the enzyme that transfers excited electrons from chlorophyll a to electron carriers of the thylakoid membrane. B) Chlorophyll a absorbs yellow light, and chlorophyll b absorbs green. C) Chlorophyll a contains magnesium in its ring structure, whereas chlorophyll b contains iron. D) Chlorophyll a and b absorb light energy at slightly different wavelengths.

D

Which of these statements is correct? A) In humans, each of the 23 maternal autosomes has a homologous paternal chromosome. B) In humans, the twenty-second pair, the sex chromosomes, determines whether the person is female (XY) or male (XX). C) Single, haploid (2n) sets of chromosomes in ovum and sperm unite during fertilization, forming a diploid (4n), single-celled zygote. D) At sexual maturity, ovaries and testes produce haploid gametes by meiosis.

D

Which process is most directly driven by light energy? A) creation of a pH gradient by pumping protons across the thylakoid membrane B) carbon fixation in the stroma C) reduction of NADP+ molecules D) removal of electrons from chlorophyll molecules E) ATP synthesis

D

Which statement describes the functioning of photosystem II? A) Light energy excites electrons in the thylakoid membrane electron transport chain. B) Photons are passed along to a reaction-center chlorophyll. C) The P680 chlorophyll donates a pair of protons to NADP+, which is thus converted to NADPH. D) The electron vacancies in P680+ are filled by electrons derived from water. E) The splitting of water yields molecular carbon dioxide as a by-product.

D

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties? A) No genes interacted to produce the parental phenotype. B) Each allele affected phenotypic expression. C) The traits blended together during fertilization. D) One allele was dominant.

D

Cinnabar eyes is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes? A) 0 percent B) 25 percent C) 50 percent D) 75 percent E) 100 percent

E

Cyclin-dependent kinase (Cdk) is ________. A) inactive, or "turned off," in the presence of cyclin B) present only during the S phase of the cell cycle C) an enzyme that removes hydroxyl groups from growth hormones D) the enzyme that catalyzes the attachment of chromosomes to microtubules E) an enzyme that attaches phosphate groups to other proteins

E

Forms of the Ras protein found in tumors usually cause which of the following? A) DNA replication to stop B) DNA replication to be hyperactive C) cell-to-cell adhesion to be nonfunctional D) cell division to cease E) excessive cell division

E

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios? A) 3 sharp-spined:1 spineless B) 1 sharp-spined:2 dull-spined:1 spineless C) 1 sharp-spined:1 dull-spined:1 spineless D) 1 sharp-spined:1 dull-spined E) 9 sharp-spined:3 dull-spined:4 spineless

E

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

E

If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O EXCEPT ________. A) 3-phosphoglycerate B) glyceraldehyde 3-phosphate (G3P) C) glucose D) ribulose bisphosphate (RuBP) E) O2

E

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 the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. 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

E

In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short? A) 1 B) 1/2 C) 1/4 D) 1/6 E) 0

E

In humans, male-pattern baldness may be assumed to be controlled by an autosomal gene that occurs in two allelic forms. Allele B determines nonbaldness, and allele b determines pattern baldness. In males, because of the presence of testosterone, allele b is dominant over B. If a man and woman both with genotype Bb have a son, what is the chance that he will eventually be bald? A) 0 percent B) 25 percent C) 33 percent D) 50 percent E) 75 percent

E

In signal transduction, phosphatases ________. A) move the phosphate group of the transduction pathway to the next molecule of a series B) prevent a protein kinase from being reused when there is another extracellular signal C) amplify the transduction signal so it affects multiple transducers D) amplify the second messengers such as cAMP E) inactivate protein kinases and turn off the signal transduction

E

In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC? A) 1/4 B) 1/8 C) 1/16 D) 1/32 E) 1/64

E

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through ________. A) plasmodesmata B) intermediate filaments C) tight junctions D) desmosomes E) gap junctions

E

Proteins that are involved in the regulation of the cell cycle and that show fluctuations in concentration during the cell cycle are called ________. A) ATPases B) kinetochores C) kinases D) estrogen receptors E) cyclins

E

Radish flowers may be red, purple, or white. The part of the radish we eat may be oval or long. A cross between a red-flowered long radish plant and a white-flowered oval radish plant yields all-purple long radish offspring. Then the F1 are crossed. In the resulting F2 generation, which of the following phenotypic ratios would be expected? A) 9:3:3:1 B) 9:4:3 C) 1:1:1:1 D) 1:1:1:1:1:1 E) 6:3:3:2:1:1

E

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents? A) XnXn and XnY B) XnXn and XNY C) XNXN and XnY D) XNXN and XNY E) XNXn and XNY

E

Sister chromatids separate from each other during ________. A) mitosis only B) meiosis I only C) meiosis II only D) mitosis and meiosis I E) mitosis and meiosis II

E

The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B? A) spindle formation B) spindle attachment to kinetochores C) DNA synthesis D) cell elongation during anaphase E) cleavage furrow formation and cytokinesis

E

The following question(s) refer to the pedigree chart in the accompanying figure for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle. What is the probability that individual III-1 is Ww? A) 3/4 B) 1/4 C) 2/4 D) 2/3 E) 1

E

The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following? A) mitosis in her ovary B) metaphase I of one meiotic event C) telophase II of one meiotic event D) telophase I of one meiotic event E) either anaphase I or II

E

There is a group of invertebrate animals called rotifers, among which a particular group of species reproduces, as far as is known, only asexually. These rotifers, however, have survived a long evolutionary history without evidence of having been overcome by excessive mutations. Since the rotifers develop from eggs, but asexually, what can you predict? A) The eggs and the zygotes are all haploid. B) The animals are all hermaphrodites. C) While asexual, both males and females are found in nature. D) All males can produce eggs. E) No fertile males can be found.

E

What do the cell walls of plants and the extracellular matrix of animal cells have in common? A) They are largely composed of phospholipids and glycoproteins. B) Their proteins are made by free cytoplasmic ribosomes. C) They form rigid structures that provide structural support for cells but limit their expansion. D) They limit the passage of small molecules. E) They have functional connections with the cytoskeleton inside the cell.

E

What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis? A) A B) B C) C D) D E) E

E

What is the primary function of the Calvin cycle? A) using ATP to release carbon dioxide B) using NADPH to release carbon dioxide C) splitting water and releasing oxygen D) transporting RuBP out of the chloroplast E) synthesizing simple sugars from carbon dioxide

E

Which of the events listed below occurs in the light reactions of photosynthesis? A) NADP is produced. B) NADPH is reduced to NADP+. C) Carbon dioxide is incorporated into PGA. D) ATP is phosphorylated to yield ADP. E) Light is absorbed and funneled to reaction-center chlorophyll a.

E

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle? A) CO2 and glucose B) H2O and O2 C) ADP, i, and NADP+ D) electrons and H+ E) ATP and NADPH

E

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

E