USABO Practice

What enzyme does HIV use to convert RNA to DNA?

Reverse Transcriptase

The promoter region of a prokaryotic gene is located ______ to the gene and is the binding site for ______.

5'...RNA polymerase

Which of the following is TRUE of prokaryotes?
I. Simultaneous transcription and translation
II. Presence of intron sequences
III. Circular DNA

I and III only

Integral transmembrane proteins are proteins imbedded in the cell membrane. Which of the following amino acids would you MOST expect to find in the transmembrane region of such proteins?

Tryptophan

When the base composition of DNA from bacterium Mycobacterium tuberculosis was determined, 18% of the bases were found to be adenine. What is the G + C content in M. tuberculosis?

64%

The frequency of individuals affected with an autosomally recessive inherited disorder is 1 in 4. Assuming that the population affected by this disease is in Hardy-Weinberg equilibrium, what is the proportion of carrier individuals in this population?

50%

The velocity of action potential conduction across a nerve axon is increased by the presence of the myelin sheath. In the peripheral nervous system, what cell myelinates the axon?

schwann cell

The cell bodies of afferent (sensory) nerves involved in somatic reflexes are located in the

Dorsal root ganglion

Rods and cones are associated with _____ and _____ vision, respectively.

Light/dark...color

Populations that are likely to be living at a density near the limit of their resources, are characterized as

K-selected

In many types of cancer, the function of the p53 gene is lost. Wild-type p53 is MOST likely to be a

tumor suppressor

What glycolytic product is shuttled to the mitochondria in aerobic respiration?

Pyruvate

During human development, which process leads to the formation of three germ layers?

gastrulation

Telomerase is responsible for _____ the size of telomeres, and its function is often ____ in carcinogenesis.

maintaining ... increased

Which of the following is NOT a mode of natural selection?

sexual selection

Protostomes have _____ and _____ types of cleavage.

spiral ... determinate

Which of the following is NOT a characteristic of all chordates?

vertebrae

In cardiac muscle, calcium ions can move freely between adjacent cells through which of the following?

gap junctions

Unlike most polypeptide hormones, steroid hormones are unique in that they

Diffuse across cell membranes

In superoxide dismutase 1, an enzyme implicated in amyotrophic lateral sclerosis (Lou Gehrig's disease), a copper ion is bound to the active site and is important for enzyme activity. In this enzyme, copper most likely functions as a(n)

cofactor

The order of normal blood flow through the human heart is

right atrium, right ventricle, lungs, left atrium, left ventricle, body

Allopatric speciation refers to species formed after which type of separation:

geographic

Which two functional groups are always found in amino acids?

Carboxyl and amine

Movement of ions across the membrane from higher to lower concentrations through a channel protein is an example of

Facilitated diffusion

Which group of plants has vascular tissue but does not produce seeds?
I. Mosses
II. Ferns
III. Gymnosperms

II

Which of the following is true for transport in xylem?

Movement through xylem depends mainly on transpiration

Predation is considered a _________ interaction, while Mutualism is considered a ___________ interaction.

+/-, +/+

Which of the following organisms is INCORRECTLY paired with its trophic level?

Beetle - secondary consumer

Which of the following is an example of habituation?

Hydra initially contract when gently touched, but soon stop responding.

Suppose gene "C" is the gene for color. Its dominant allele has the effect of allowing the production of fur color while its recessive allele interrupts color production. At another locus, there exists another gene that influences color, at which black (B) is dominant to brown (b). What is the relationship between these genes called?

Epistatic

During migrations, some birds use which of the following as reference frameworks?
I. The sun
II. Constellations
III. Earth's magnetic field

I,II, and III

Generally, there are more species per square kilometer in which of the following types of ecosystem?

Coral reef

RUBP is used and PGA is formed in:

dark reaction (Calvin cycle) of photosynthesis

Which is TRUE of the dark reaction (Calvin cycle) of photosynthesis?

It uses carbon dioxide

In the fern life cycle, the dominant generation is the:

diploid sporophyte

Assume a person is placed on cortisol medication, a glucocorticoid. How would you expect the rates of ACTH and CRF hormone production to change in the person?

ACTH production would decrease, CRF production would increase

Carbon particles were injected into the blood of mice. In which of the following places would you most likely find the particles?

In monocytes of the spleen

Kidneys provide osmoregulation for the body. Consumption of which nutrient creates the greatest need for osmoregulation?

Protein

During translation in prokaryotes, the ribosome binds to:

the Shine-Dalgarno sequence

The quaternary structure of a protein is determined by:

.interactions between amino acids of different polypeptide chains.

Which of the following is not a function of the parasympathetic division of the nervous system?

. Stimulation of the adrenal medulla

You place a growing seedling in an east-facing window. On which side of the plant will active auxin accumulate?

West side

Which of the following is NOT a characteristic of all mammalian species?

Placenta

Suppose the lac repressor of E. coli is mutated so that it never binds to the operator. Which of the following is true?

The result depends on the concentration of glucose

You examine a leaf cross-section under a microscope and find many loosely packed cells. These cells have many chloroplasts and relatively thin cell walls. These cells are:

Parenchyma

For the biomass pyramid shown below, choose the correct statement.
secondary consumer
primary consumer producer (see question 11 on 2004 exam)

Producers reproduce quickly but are also consumed at a rapid rate

Which of the following would be most likely to increase competition among the members of the vole population in a given area?

An increase in the reproduction rate of voles

Tobacco mosaic virus has RNA rather than DNA as its genetic material. If the RNA genome from a tobacco mosaic virus is mixed with proteins from a human rhinovirus, the result is a mixed virus. If that virus could infect a cell and reproduce, what would you expect the resulting viruses to be like?

Tobacco Mosaic Virus

An amphipathic molecule is a molecule that is characterized by:

A hydrophilic end and a hydrophobic end

The function of a molecular chaperone is to

bind to specific structures on the polypeptide in order to assist the folding of a protein into its correct three dimensional shape.

Ethidium Bromide is used in electrophoresis of DNA fragments because it:

makes the fragments visible under UV light.

The species Homo sapiens first appeared in which geologic epoch?

Pleistocene

Which of the following marine communities would be LEAST affected by a volcanic eruption or meteor impact that injected enough debris into the atmosphere to reduce sunlight by 50% for two years?

Deep sea vent community

A unique feature of fertilization in angiosperms is that:

it is a double fusion event; one sperm fertilizes the egg, the other sperm combines with the polar or fusion nucleus.

Which statement describing plant structure is appropriate?

Sclerenchyma cells provide support for the plant body

The Hardy-Weinberg equilibrium principle assumes all of the following statements EXCEPT:

. for a given trait the frequency of dominant alleles is greater than that of recessive alleles.

Professor Jones is running an experiment with his graduate students in his physiology lab. One group of students drinks a liter of water, another group drinks a liter of coffee, and a third group drinks a liter of concentrated salt solution. The volume of urine produced by all individuals in the three groups is measured over a period of several hours. At the end of the monitoring period, which group will have produced the greatest volume of urine and which group the least?

Those who drank coffee will produce the most urine, while those who drank the salt solution will produce the least

A protein is usually tagged for degradation by proteasome activity by which of the following proteins?

Ubiquitin

Which of the following statements is true of territorial behavior?

"Owners" defend mainly against conspecifics

You extract RNA from liver cells and then carry out an agarose gel electrophoresis of the liver RNA. The RNA fragments are then transferred to an RNA-binding membrane (nitrocellulose or nylon) using capillary action. Next, you hybridize a probe for gene X to the RNA on the membrane. Which of the following statements regarding your experiment is true?

. You are trying to determine if Gene X is expressed in liver cells

A toxin exists that inhibits the enzyme succinate dehydrogenase. If this were used in an experiment to stop respiration, how many net NADH and ATP molecules would be generated from each pyruvate molecule during pyruvate oxidation and the citric acid cycle up to that stage?

3, 1

Which of the following characteristics is an adaptation of temperate climatic zone plants?

Dormant buds

Which of the following statements is acceptable?

A long day plant will flower if it has over a half day of darkness interrupted by a short flash of light

Which of the following is NOT a second messenger?

Magnesium ion

The reduction phase of the Calvin cycle is equivalent to which of the following processes in reverse?

Energy payoff phase of glycolysis

Which of the choices below correctly ranks [from least to greatest] the contribution of the various ecosystems as to their "Average Net Primary Production per unit area (kcal/m2/yr)"?

Open ocean, savanna, temperate forest, tropical rain forest

In most terrestrial mammalian species, parental investment is greater for female parents than for male parents. This is because:

females are typically 'K-selected', whereas males are more often 'r-selected'.

Which of the following is part of the egg-producing structure in plants?

The megagametophyte of angiosperms

A booster dose of a vaccination helps to:

increase the blood antibody level by increasing the number of effector cells.

In mice, one gene regulates color. Homozygous recessive organisms are white, homozygous dominant organisms are black, and some organisms exhibit incomplete dominance (gray fur). A gray male and a gray female produce an offspring of unknown gender. What is the probability that the mouse will NOT be born with white fur?

3/4

The most phytoplankton in a lake would be found in which zone?

Limnetic Zone

Hemoglobin, an iron-containing protein in erythrocytes, binds oxygen molecules. Myoglobin, a protein in muscle cells, is used for oxygen storage. What can be deduced about the relative oxygen affinities of hemoglobin and myoglobin?

. Myoglobin has greater oxygen affinity than hemoglobin

In an experiment, a plant is grown at a particular level of light and in a certain concentration of CO2. With CO2 constant and light intensity gradually increasing to a preset level, oxygen production increases up to a point and then levels off. If light is increased beyond the preset level, no further increase in oxygen production is noted. In a second experiment, the same increasing regimen of light is used, but a higher level of CO2 is supplied. O2 production in the second experiment continues to increase beyond the point where it leveled off in the first experiment. From these observations, one might conclude:

light is limiting up to a point and then CO2 becomes a limiting factor.

Plant systematicists have found that monocots were not the first flowering plants to evolve. This would suggest that:

evolution does not always proceed from simple to complex.

In a certain population of 100 deer, 34 births and 25 deaths were recorded in one year. Assuming no immigration or emigration occurred, what is r for that population?

0.09

A patient is suffering from kidney failure. Which of the following symptoms will most likely be present in this patient?

A higher salt concentration in the blood

An investigator found 150 different diatom species in one mile of a stream. None of the species comprised more than 5% of the total population. In a second observation twenty-five miles downstream, there were only 20 different diatom species, with 2 species representing 80% of the total population. What is the best explanation of these two observations?

Organic wastes high in nitrates and phosphates entered the stream somewhere between the two sampling stations

Which of the following statements is an acceptable statement about growth in plants?

Some plants lack secondary growth

ATP is an important molecule in metabolism because it:

has high-energy phosphate bonds.

Crossing over contributes to the genetic variation of a species by exchanging chromosomal segments between nonsister chromatids of homologous chromosomes. In the production of which type of cell does the crossing over occur?

Gametes

In a population of 15 AA, 25 Aa, and 10 aa individuals, the frequency of the a allele is:

0.45

Use the cladogram below to answer the following question. Which group(s) represent(s) a monophyletic taxon? (number 47 on 2004 exam)

A, B, C, D, E, F, and G

A ribozyme is a(an):

RNA molecule that functions as a enzyme.

When an ant in a colony dies, the live ants will throw the dead ant out of the anthill. If a live ant from the colony, Ant X, is sprayed with a chemical characteristic of dead ants, the live ants will repeatedly throw Ant X out of the anthill, until the chemical on Ant X wears off. What is the best behavioral explanation of ant colony?

The chemical acts as a sign stimulus for a fixed action pattern

Vascular plants share all of the following characteristics EXCEPT:

development of seeds.

The production of the genetically engineered "golden rice" could be important to the people of developing nations, especially in South-East Asia, because:

golden rice contains higher concentrations of β-carotene than white rice

A large population of laboratory rats was allowed to breed randomly for a number of generations. In this population, a dominant allele at the A locus codes for agouti fur (A), and a recessive allele codes for black fur (a). At the beginning of the breeding cycles, 49% of the rats had black fur. At the end of the breeding cycles, this percentage was the same. The rest of the animals had agouti fur with heterozygotes indistinguishable from homozygous dominants. What percentage of this population is probably heterozygous for the fur color trait assuming the rats are following Hardy-Weinberg population genetics?

42%

In Pompe's disease, the liver is damaged due to the accumulation of glycogen. What organelle is most likely malfunctioning?

lysosome

Transport of which nutrient across the intestinal epithelium is by passive diffusion?

fructose

Which two brain centers control mammalian respiration?

medulla oblongata and pons

The presence of a vertebral column is with respect to all vertebrates [first term], but is with respect to all chordates [second term].

primitive; derived

The main explanation for the lack of a continuing abiotic origin of life on Earth today is that:

our oxidizing atmosphere is not conducive to spontaneous formation of complex molecules

Scientists have determined that three classes of genes (named A, B, and C) control development of the four flower parts: Sepals, Petals, Stamen, and Carpels. Genes A and C mutually repress each other. Gene B is not regulated by either Genes A or C. The expression pattern of these genes in wild-type flowers is shown below, where +++ indicates gene activity.
A mutation in Gene C, which prevents its expression, will result in which of the following floral patterns? (question 8 of 2005 exam)

Sepals-Petals-Petals-Sepals

An inbred strain of plants has a mean height of 24 cm. A second strain of the same species also has a mean height of 24 cm. When these plants are crossed, the F1 are also 24 cm. However, when the F1 plants are crossed, the F2 plants show a wide range of heights; the majority of F2 are like P1 and F1, but approximately 4 of 1000 are only 12 cm tall and 4 of 1000 are 36 cm tall. What fraction of the F2 plants will be 27 cm in height? [Assume that for the genes involved in determining plant height, each allele contributes the same amount.]

56/256

To be functional, a linear chromosome most often contains at least:

two telomeres, one centromere, and a large number of origins of replication

Which of the following subdivisions of the autonomic nervous system would be most important to a zebra fleeing from a lion?

the sympathetic nervous system

To keep their dog breeds "pure," breeders will keep dogs of different breeds in physically separate areas when the female is in heat. This aspect of artificial selection is most closely analogous to which of the following reproductive isolating mechanisms?

ecological isolation

A man and a woman get married and soon learn that they both have a rare, genetically inherited recessive disease that makes them prone to migraine headaches. Worried about the fate of their children, they seek the advice of a genetic counselor. He sequences their genomes and assures them that none of their children will have the disease. What information did he have to obtain from the sequencing procedure to make this claim?

The man and the woman have mutations in different genes that result in the same migraine headache phenotype.

You are trying to isolate glyoxysomes and peroxisomes from a mixture of cellular organelles using differential centrifugation. After a few centrifugation steps, you think you may have a relatively pure suspension. How might you determine that your suspension does indeed include these organelles?

do an assay for the enzyme catalase

An animal experiences an acid-base imbalance in the arterial blood that results in acidosis. To increase pH toward normal, which direction would the ventilation rate be changed and what would be the corresponding change in arterial PCO2?

ventilation rate increases, arterial PCO2 decreases