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biocore final exam

Pregunta 1 de 100

1

The text states that ribonucleotides can diffuse through some types of liposomes. It is likely that the lipids present early in chemical evolution had short chains. Would liposomes formed from these types of lipids be more or less permeable to ribonucleotides than if early cells formed from long-chained lipids?

Selecciona una de las siguientes respuestas posibles:

  • Same permeability

  • less permeable

  • more permeable

Explicación

Pregunta 2 de 100

1

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 _____.

Selecciona una de las siguientes respuestas posibles:

  • an animal cell in the process of cytokinesis

  • an animal cell in the S phase of the cell cycle

  • a plant cell in the process of cytokinesis

  • a plant cell in metaphase

  • a bacterial cell dividing

Explicación

Pregunta 3 de 100

1

After telophase I of meiosis, the chromosomal makeup of each daughter cell is _____.

Selecciona una de las siguientes respuestas posibles:

  • haploid, and the chromosomes are each composed of a single chromatid

  • diploid, and the chromosomes are each composed of a single chromatid

  • tetraploid, and the chromosomes are each composed of two chromatids

  • haploid, and the chromosomes are each composed of two chromatids

  • diploid, and the chromosomes are each composed of two chromatids

Explicación

Pregunta 4 de 100

1

Which of the following did Watson and Crick already know when they were trying to determine the structure of DNA? The number of _____.

Selecciona una de las siguientes respuestas posibles:

  • cytosines is always the same as adenines

  • purines is always larger than the number of pyrimidines

  • purines is always the same as pyrimidines

  • guanines is always the same as thymines

  • pyrimidines is always larger than purines

Explicación

Pregunta 5 de 100

1

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental
varieties?

Selecciona una de las siguientes respuestas posibles:

  • No genes interacted to produce the parental phenotype.

  • One allele was dominant.

  • Each allele affected phenotypic expression.

  • The traits blended together during fertilization.

Explicación

Pregunta 6 de 100

1

Independent assortment of chromosomes occurs during _____.

Selecciona una de las siguientes respuestas posibles:

  • mitosis and meiosis I

  • mitosis and meiosis II

  • meiosis II only

  • meiosis I only

  • Mitosis only

Explicación

Pregunta 7 de 100

1

How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? They have _____.

Selecciona una de las siguientes respuestas posibles:

  • twice the amount of cytoplasm and half the amount of DNA.

  • half the number of chromosomes and half the amount of DNA.

  • half the amount of cytoplasm and twice the amount of DNA.

  • the same number of chromosomes and half the amount of DNA.

  • half the number of chromosomes and one-fourth the amount of DNA.

Explicación

Pregunta 8 de 100

1

The fastest way for organisms to adapt to a changing environment involves _____.

Selecciona una de las siguientes respuestas posibles:

  • Sexual reproduction

  • Mutation

  • Asexual reproduction

Explicación

Pregunta 9 de 100

1

Crossing over normally takes place during which of the following processes?

Selecciona una de las siguientes respuestas posibles:

  • meiosis I

  • Mitosis and meiosis II

  • Meiosis II

  • Mitosis

Explicación

Pregunta 10 de 100

1

In comparison to eukaryotes, prokaryotes _____.

Selecciona una de las siguientes respuestas posibles:

  • are smaller

  • are more structurally complex

  • do not have membranes

  • are larger

Explicación

Pregunta 11 de 100

1

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?

Selecciona una de las siguientes respuestas posibles:

  • 40

  • 80

  • 10

  • 20

  • It is impossible to tell from the information given.

Explicación

Pregunta 12 de 100

1

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). These two
regions of the promoter _____.

Selecciona una de las siguientes respuestas posibles:

  • bind the sigma subunit that is associated with RNA polymerase

  • signal the initiation site

  • attach the correct nucleotide triphosphate to the template DNA strand

  • separate the two DNA strands

Explicación

Pregunta 13 de 100

1

Why is it that RNA can catalyze reactions but DNA cannot?

Selecciona una de las siguientes respuestas posibles:

  • The primary structure of RNA is fundamentally different than the primary structure of DNA.

  • The phosphate groups of RNA are much more reactive than the phosphate groups of DNA.

  • The bases of RNA are much more reactive than the bases of DNA.

  • The sugar of RNA is much more reactive than the sugar of DNA.

Explicación

Pregunta 14 de 100

1

Some cells have several nuclei per cell. How could such multinucleated cells be explained?

Selecciona una de las siguientes respuestas posibles:

  • The cell had multiple S phases before it entered mitosis.

  • The cell underwent repeated cytokinesis but no mitosis.

  • The cell underwent repeated mitosis, but cytokinesis did not occur.

  • The cell underwent repeated mitosis with simultaneous cytokinesis.

Explicación

Pregunta 15 de 100

1

A water sample from a hot thermal vent contained a single-celled organism that had a cell wall but lacked a nucleus. What is its most likely classification?

Selecciona una de las siguientes respuestas posibles:

  • Eukarya

  • Fungi

  • Animalia

  • Protista

  • Archaea

Explicación

Pregunta 16 de 100

1

In the figure above, mitosis is represented by which numbered part(s) of the cycle?

Selecciona una de las siguientes respuestas posibles:

  • I

  • II

  • III

  • IV

  • V

Explicación

Pregunta 17 de 100

1

The first gap in the cell cycle (G1) corresponds to _____.

Selecciona una de las siguientes respuestas posibles:

  • normal growth and cell function

  • the phase between DNA replication and the M phase

  • the beginning of mitosis

  • the phase in which DNA is being replicated

Explicación

Pregunta 18 de 100

1

In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotypeBB 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?

Selecciona una de las siguientes respuestas posibles:

  • 100%

  • 25%

  • about 66%

  • 50%

  • 33%

Explicación

Pregunta 19 de 100

1

What is the process component of the theory of chemical evolution?

Selecciona una de las siguientes respuestas posibles:

  • The process occurred at black smokers, in the atmosphere and oceans, or in outer space.

  • During polymerization reactions, hydrolysis was completed with condensation.

  • Kinetic energy was transformed into chemical energy.

  • Acid-base reactions resulted in the formation of large, complex organic molecules.

Explicación

Pregunta 20 de 100

1

Mitosis separates chromosomes. Cytoplasm is divided between two daughter cells by _____.

Selecciona una de las siguientes respuestas posibles:

  • cytokinesis

  • Binary fission

  • the formation of kinetochores

  • cloning

Explicación

Pregunta 21 de 100

1

Some viruses consist only of a protein coat surrounding a nucleic acid core. If you wanted to radioactively label the nucleic acids separately from the protein, you would use radioactive

Selecciona una de las siguientes respuestas posibles:

  • nitrogen

  • sulfur

  • phosphorus

  • carbon

Explicación

Pregunta 22 de 100

1

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 _____.

Selecciona una de las siguientes respuestas posibles:

  • formation of the centrioles

  • chromatid assembly

  • the S phase of the cell cycle

  • the structure of the mitotic spindle

  • anaphase

Explicación

Pregunta 23 de 100

1

What is the structural feature that allows DNA to replicate?

Selecciona una de las siguientes respuestas posibles:

  • disulfide bonding (bridging) of the two helixes

  • complementary pairing of the nitrogenous bases

  • twisting of the molecule to form an α-helix

  • sugar-phosphate backbone

  • three-component structure of the nucleotides

Explicación

Pregunta 24 de 100

1

Your colleague proposes to test the mechanism of ant navigation by placing a food source 7 meters (m) from the nest. She then takes ants from the nest and places them in a spot that is 4 m from the nest and 3 m from the food source. Based on the previous data, where do you expect the ants to start searching for their nest on their return trip?

Selecciona una de las siguientes respuestas posibles:

  • after they have traveled 7 m from the food source

  • after they have traveled 4 m from the food source

  • after they have traveled 3 m from the food source

  • as soon as they leave the food source

Explicación

Pregunta 25 de 100

1

Refer to the figure above. What is the function of the AGU on the loop of the tRNA?

Selecciona una de las siguientes respuestas posibles:

  • It is the active site of this ribozyme.

  • It attaches to the amino acid.

  • It stabilizes the tRNA-amino acid complex.

  • It base pairs with a codon of mRNA

Explicación

Pregunta 26 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • codominant

  • recessive

  • incomplete dominant

  • dominant

Explicación

Pregunta 27 de 100

1

Movement of the chromosomes during anaphase would be most affected by a drug that prevents _____.

Selecciona una de las siguientes respuestas posibles:

  • elongation of microtubules

  • shortening of microtubules

  • nuclear envelope breakdown

  • cell wall formation

  • formation of a cleavage furrow

Explicación

Pregunta 28 de 100

1

If a cell has accumulated DNA damage, it is unlikely to _____.

Selecciona una de las siguientes respuestas posibles:

  • enter G1 from mitosis

  • pass the G2 checkpoint

  • synthesize cyclin-dependent kinases

  • activate DNA repair mechanisms

Explicación

Pregunta 29 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • 9/16

  • 3/4

  • 1/16

  • 1/2

  • 1/8

Explicación

Pregunta 30 de 100

1

The work of Gregor Mendel provided an answer to two prevailing hypotheses popular at the time. What were these two hypotheses?

Selecciona una de las siguientes respuestas posibles:

  • Peas and other domestic plants are unsuited for studies of inheritance, but wild plants are perfectly suited.

  • Animals use one set of rules for inheritance, while plants use a different set.

  • Mitosis is only typical in vertebrates. Meiosis is only typical in invertebrates.

  • The two major hypotheses of the time were blending inheritance and inheritance of acquired characteristics.

  • Self-fertilization is the rule in plants, while cross-fertilization is the rule in animals.

Explicación

Pregunta 31 de 100

1

In the context of chemical evolution, DNA's structure is interesting because it suggests a possible copying mechanism. What about DNA's structure facilitates copying?

Selecciona una de las siguientes respuestas posibles:

  • The strands of the double helix are complementary.

  • It has the same number of purines and pyrimidines.

  • DNA always goes from 5 prime to 3 prime.

  • The nitrogenous bases are located on the inside of the double helix.

Explicación

Pregunta 32 de 100

1

Which of the following is a true statement about sexual vs. asexual reproduction?

Selecciona una de las siguientes respuestas posibles:

  • Asexual reproduction produces only haploid offspring.

  • In asexual reproduction, offspring are produced by fertilization without meiosis.

  • In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.

  • Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi.

  • Sexual reproduction requires that parents be diploid.

Explicación

Pregunta 33 de 100

1

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)?

Selecciona una de las siguientes respuestas posibles:

  • 8

  • 4

  • 32

  • 16

  • 2

Explicación

Pregunta 34 de 100

1

Which of these provides evidence of the common ancestry of all life?

Selecciona una de las siguientes respuestas posibles:

  • structure of cilia

  • structure of the nucleus

  • structure of chloroplasts

  • ubiquitous use of catalysts by living systems

  • near universality of the genetic code

Explicación

Pregunta 35 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • M

  • G1

  • S

  • G0

  • G2

Explicación

Pregunta 36 de 100

1

About thirteen different species of finches inhabit the Galápagos Islands today, all descendants of a common ancestor from the South American mainland that arrived a few million years ago. Genetically, there are four distinct lineages, but the thirteen species are currently classified among three genera. The first lineage to diverge from the ancestral lineage was the warbler finch (genus Certhidea). Next to diverge was the vegetarian finch (genus Camarhynchus), followed by five tree finch species (also in genus Camarhynchus) and six ground finch species (genus Geospiza). If the six ground finch species have evolved most recently, then which of these is the most logical prediction?

Selecciona una de las siguientes respuestas posibles:

  • They should be limited to the six islands that most recently emerged from the sea.

  • The chances of hybridization between two ground finch species should be less than the chances of hybridization between two tree finch species.

  • Their genomes should be more similar to each other than are the genomes of the five tree finch species.

  • They should share fewer anatomical homologies with each other than they share with the tree finches.

Explicación

Pregunta 37 de 100

1

In eukaryotic cells, chromosomes are composed of _____.

Selecciona una de las siguientes respuestas posibles:

  • DNA and proteins

  • DNA and phospholipids

  • DNA and RNA

  • DNA only

Explicación

Pregunta 38 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • cleavage furrow formation and cytokinesis

  • spindle formation

  • DNA synthesis

  • cell elongation during anaphase

  • spindle attachment to kinetochores

Explicación

Pregunta 39 de 100

1

Which of the following is the best modern definition of evolution?

Selecciona una de las siguientes respuestas posibles:

  • change in the number of genes in a population over time

  • inheritance of acquired characters

  • descent with modification

  • survival of the fittest

Explicación

Pregunta 40 de 100

1

An advantage of asexual reproduction is that it _____.

Selecciona una de las siguientes respuestas posibles:

  • allows a species to easily rid itself of harmful mutations

  • enables the species to rapidly colonize habitats that are favorable to that species

  • produces offspring that respond effectively to new pathogens

  • allows the species to endure long periods of unstable environmental conditions

  • enhances genetic variability in the species

Explicación

Pregunta 41 de 100

1

Which of the following are qualities of any good scientific hypothesis?
I. It is testable.
II. It is falsifiable.
III. It produces quantitative data.
IV. It produces results that can be replicated.

Selecciona una de las siguientes respuestas posibles:

  • I only

  • II only

  • III only

  • I and II

  • III and IV

Explicación

Pregunta 42 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • red and long

  • purple and long

  • ren and oval

  • purple and oval

  • white and long

Explicación

Pregunta 43 de 100

1

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.
-Which of the following questions might be answered by using the method described?

Selecciona una de las siguientes respuestas posibles:

  • When do spindle fibers attach to chromosomes?

  • How many cells are produced by the culture per hour?

  • What is the length of the S phase of the cell cycle?

  • How many picograms of DNA are made per cell cycle?

  • When is the S chromosome synthesized?

Explicación

Pregunta 44 de 100

1

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 _____.

Selecciona una de las siguientes respuestas posibles:

  • their tissue culture methods needed to be relearned

  • infection causes lymphocyte cultures to skip some parts of the cell cycle

  • infection causes cell cultures in general to reproduce more rapidly

  • the presence of the pathogen made the experiments too contaminated to trust the results

  • infection causes lymphocytes to divide more rapidly

Explicación

Pregunta 45 de 100

1

If a cell has completed meiosis I and is just beginning meiosis II, which of the following is an appropriate description of its contents?

Selecciona una de las siguientes respuestas posibles:

  • It has half the amount of DNA as the cell that began meiosis.

  • It is identical in content to another cell formed from the same meiosis I event.

  • It has the same number of chromosomes, but each of them has different alleles than another cell from the same meiosis.

  • It has one-fourth the DNA and one-half the chromosomes as the originating cell.

  • It has half the chromosomes but twice the DNA of the originating cell.

Explicación

Pregunta 46 de 100

1

Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct?

Selecciona una de las siguientes respuestas posibles:

  • the 5' end has a carboxyl group attached to the number 5 carbon of ribose.

  • the 5' end is the fifth position on one of the nitrogenous bases.

  • the 5' end has a hydroxyl group attached to the number 5 carbon of ribose.

  • the 5' end has phosphate attached to the number 5 carbon of the nitrogenous base.

  • the 5' end has a phosphate group attached to the number 5 carbon of ribose.

Explicación

Pregunta 47 de 100

1

GeneS controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele,S, have sharp spines, whereas homozygous recessivess 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_____.

Selecciona una de las siguientes respuestas posibles:

  • all spineless progeny

  • all sharp-spined progeny

  • 50% sharp-spined, 50% dull-spined progeny

  • 25% sharp-spined, 50% dull-spined, 25% spineless progeny

  • It is impossible to determine the phenotypes of the progeny.

Explicación

Pregunta 48 de 100

1

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.)

Selecciona una de las siguientes respuestas posibles:

  • (a) GG ×gg; (b) genotypic = 3:1, phenotypic = 1:2:1

  • (a) gg ×Gg; (b) genotypic = 1:2, phenotypic = 3:1

  • (a) Gg ×Gg; (b) genotypic = 3:1, phenotypic = 9:3:3:1

  • (a) GG ×Gg; (b) genotypic = 1:2:1, phenotypic = 2:1

  • (a) Gg ×Gg; (b) genotypic = 1:2:1, phenotypic = 3:1

Explicación

Pregunta 49 de 100

1

Suppose that an induced mutation removes most of the 5′ end of the 5′ UTR of an mRNA. What is most likely to happen?

Selecciona una de las siguientes respuestas posibles:

  • Removal of the 5′ UTR also removes the 5' cap and the mRNA will quickly degrade.

  • Removal of the 5′ UTR will have no effect because the exons are still maintained.

  • The 3′ UTR will duplicate and one copy will replace the 5′ end.

  • The first exon will not be read because I1 will now serve as the UTR.

Explicación

Pregunta 50 de 100

1

Refer to the accompanying figure. Recall that eggs from the same female were exposed to each of the eight treatments used. This aspect of the experimental design tested which of the following hypotheses?

Selecciona una de las siguientes respuestas posibles:

  • Differences in diet trigger the development of different types of caterpillars.

  • The differences are genetic. A female will either produce all flowerlike caterpillars or all twig-like caterpillars.

  • The longer day lengths of summer trigger the development of twig-like caterpillars.

  • Differences in air pressure, due to elevation, trigger the development of different types of caterpillars.

Explicación

Pregunta 51 de 100

1

Refer to the accompanying figure. In every case, caterpillars that feed on oak flowers look like oak flowers. In every case, caterpillars that were raised on oak leaves looked like twigs. These
results support which of the following hypotheses?

Selecciona una de las siguientes respuestas posibles:

  • The differences are genetic. A female will either produce all flowerlike caterpillars or all twig-like caterpillars.

  • The longer day lengths of summer trigger the development of twig-like caterpillars.

  • Differences in air pressure, due to elevation, trigger the development of different types of caterpillars.

  • Differences in diet trigger the development of different types of caterpillars.

Explicación

Pregunta 52 de 100

1

Refer to the accompanying figure. Which one of the following is NOT a plausible hypothesis to explain the differences in caterpillar appearance observed in this population?

Selecciona una de las siguientes respuestas posibles:

  • The cooler temperatures of spring trigger the development of flowerlike caterpillars.

  • The longer day lengths of summer trigger the development of twig-like caterpillars.

  • Differences in air pressure, due to differences in elevation, trigger the development of different types of caterpillars.

  • Differences in diet trigger the development of different types of caterpillars.

Explicación

Pregunta 53 de 100

1

Steroid hormones are large communication molecules that are modified cholesterol molecules. How do you think they enter a cell?

Selecciona una de las siguientes respuestas posibles:

  • Their lipid nature probably allows them to diffuse through the plasma membrane.

  • Their size probably allows them to diffuse through the plasma membrane.

  • Their protein structure probably allows them to diffuse through the plasma membrane.

  • They must require a protein transporter, because the plasma membrane is completely impermeable to molecules.

Explicación

Pregunta 54 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • All of the genes controlling the traits were located on the same chromosome.

  • All of the genes controlling the traits behaved as if they were on different chromosomes.

  • The formation of gametes in plants occurs by mitosis only.

  • None of the traits obeyed the law of segregation.

  • The diploid number of chromosomes in the pea plants was 7.

Explicación

Pregunta 55 de 100

1

During which phase of mitosis do the chromatids become chromosomes?

Selecciona una de las siguientes respuestas posibles:

  • prophase

  • cytokinesis

  • telophase

  • metaphase

  • anaphase

Explicación

Pregunta 56 de 100

1

Researchers pulsed rapidly dividing cultured cells with radioactive thymidinefor 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:

Selecciona una de las siguientes respuestas posibles:

  • 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.

  • 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.

  • Radiolabeled compounds are somewhat cytotoxic, and cell division was initially inhibited.

  • There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.

Explicación

Pregunta 57 de 100

1

Which of the following evidence most strongly supports the common origin of all life on Earth? All organisms _____.

Selecciona una de las siguientes respuestas posibles:

  • require energy

  • use essentially the same genetic code

  • evolve

  • show heritable variation

  • reproduce

Explicación

Pregunta 58 de 100

1

In eukaryotic cells, transcription cannot begin until _____.

Selecciona una de las siguientes respuestas posibles:

  • the DNA introns are removed from the template

  • the two DNA strands have completely separated and exposed the promoter

  • the 5′ caps are removed from the mRNA

  • DNA nucleases have isolated the transcription unit

  • several transcription factors have bound to the promoter

Explicación

Pregunta 59 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • epistasis

  • codominance

  • multiple alleles

  • incomplete dominance

  • pleiotropy

Explicación

Pregunta 60 de 100

1

RNA and proteins combine in cells to form structures called ribosomes. Ribosomes contain the active site for peptide bond formation. Based on their chemical structures, do you think protein
or RNA molecules actually form the active site within the ribosome?

Selecciona una de las siguientes respuestas posibles:

  • RNA, because proteins cannot catalyze a reaction that involves another protein

  • protein, because RNA cannot catalyze reactions

  • It could be either, because both molecules have catalytic properties.

  • proteins, because only proteins can catalyze a reaction that involves another protein

Explicación

Pregunta 61 de 100

1

What is responsible for termination of transcription in eukaryotic protein-coding genes?

Selecciona una de las siguientes respuestas posibles:

  • three nonsense mutations in sequence

  • a polyadenylation signal or poly(A)

  • a portion of the polymerase holoenzyme

  • a sigma factor

  • a termination loop composed of guanine

Explicación

Pregunta 62 de 100

1

Both DNA and RNA _____.

Selecciona una de las siguientes respuestas posibles:

  • are information-containing molecules

  • show primary, secondary, tertiary, and quaternary structure

  • naturally occur as a double helix

  • are highly reactive catalysts in cells

Explicación

Pregunta 63 de 100

1

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to _____.

Selecciona una de las siguientes respuestas posibles:

  • disruption of mitotic spindle formation

  • suppression of cyclin production

  • myosin denaturation and inhibition of cleavage furrow formation

  • inhibition of DNA synthesis

  • inhibition of regulatory protein phosphorylation

Explicación

Pregunta 64 de 100

1

If there are 20 chromatids in a cell, how many centromeres are there?

Selecciona una de las siguientes respuestas posibles:

  • 30

  • 20

  • 80

  • 10

  • 40

Explicación

Pregunta 65 de 100

1

Genetic mutations in asexually reproducing organisms lead to more evolutionary change than do genetic mutations in sexually reproducing ones because _____.

Selecciona una de las siguientes respuestas posibles:

  • sexually reproducing organisms can produce more offspring in a given time than can asexually reproducing organisms

  • asexually reproducing organisms have more dominant genes than organisms that reproduce sexually

  • asexually reproducing organisms devote more time and energy to the process of reproduction than do sexually reproducing organisms

  • asexually reproducing organisms, but not sexually reproducing organisms, pass all mutations on to their offspring

  • more genetic variation is present in organisms that reproduce asexually than is present in those that reproduce sexually

Explicación

Pregunta 66 de 100

1

In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit _____.

Selecciona una de las siguientes respuestas posibles:

  • the attachment of microtubules to kinetochores

  • the splitting of the centrosomes

  • the disassembly of the nucleolus

  • cytokinesis

Explicación

Pregunta 67 de 100

1

A cell in late anaphase of mitosis will have _____.

Selecciona una de las siguientes respuestas posibles:

  • no chromosomes in the center of the cell

  • one large nuclear envelope

  • individual chromatids beginning to separate from one another

  • chromosomes clustered at one end of the cell

  • chromosomes clustered tightly at the center

Explicación

Pregunta 68 de 100

1

Compare proteins to nucleic acids. Which of the following is true?

Selecciona una de las siguientes respuestas posibles:

  • Both contain sulfur.

  • Both take on structural roles in the cell.

  • Both have primary and secondary structure.

  • Both have monomers, which contain phosphorus.

Explicación

Pregunta 69 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • Only if a woman is XXX could she have this condition.

  • Women can never have this condition.

  • One-half of the daughters of an affected father and a carrier mother could have this condition.

  • One-fourth of the daughters of an affected man would have this condition.

Explicación

Pregunta 70 de 100

1

Cells are _____.

Selecciona una de las siguientes respuestas posibles:

  • characteristic of prokaryotic and eukaryotic organisms

  • characteristic of eukaryotic but not prokaryotic organisms

  • limited in size to 200 and 500 micrometers in diameter

  • only found in pairs, because single cells cannot exist independently

Explicación

Pregunta 71 de 100

1

Which of these statements is correct?

Selecciona una de las siguientes respuestas posibles:

  • Single, haploid (2n) sets of chromosomes in ovum and sperm unite during fertilization, forming a diploid (4n), single-celled zygote.

  • At sexual maturity, ovaries and testes produce haploid gametes by meiosis.

  • In humans, each of the twenty-three maternal autosomes has a homologous paternal chromosome.

  • In humans, the twenty-second pair, the sex chromosomes, determines whether the person is female (XY) or male (XX).

Explicación

Pregunta 72 de 100

1

Which of the following best describes the logic of scientific inquiry?

Selecciona una de las siguientes respuestas posibles:

  • If my hypothesis is correct, I can expect certain test results.

  • If my prediction is correct, it will lead to a testable hypothesis.

  • If my experiments are set up right, they will lead to a testable hypothesis.

  • If I generate a testable hypothesis, tests and observations will support it.

  • If my observations are accurate, they will support my hypothesis.

Explicación

Pregunta 73 de 100

1

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 _____.

Selecciona una de las siguientes respuestas posibles:

  • crossing over

  • independent assortment

  • nothing else

  • crossing over and independent assortment

Explicación

Pregunta 74 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • phenotype

  • haplotype

  • category

  • genotype

  • appearance

Explicación

Pregunta 75 de 100

1

Darwin and Wallace's theory of evolution by natural selection was revolutionary because it _____.

Selecciona una de las siguientes respuestas posibles:

  • proved that individuals acclimated to their environment over time

  • was the first theory to refute the ideas of special creation

  • was the first time a biologist had proposed that species changed through time

  • dismissed the idea that species are constant and emphasized the importance of variation and change in populations

Explicación

Pregunta 76 de 100

1

Which of the following could be considered an evolutionary advantage of asexual reproduction in plants?

Selecciona una de las siguientes respuestas posibles:

  • production of numerous progeny.

  • increased agricultural productivity in a rapidly changing environment.

  • maintenance and expansion of a large genome.

  • increased success of progeny in a stable environment.

  • increased ability to adapt to a change in the environment.

Explicación

Pregunta 77 de 100

1

If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?

Selecciona una de las siguientes respuestas posibles:

  • phospholipids

  • DNA

  • both DNA and RNA

  • RNA

  • proteins

Explicación

Pregunta 78 de 100

1

A controlled experiment _____.

Selecciona una de las siguientes respuestas posibles:

  • proceeds at a slow pace to guarantee that the scientist can carefully observe all reactions and process all experimental data

  • includes one group for which the scientist controls all variables

  • is repeated many times to ensure that the results are accurate

  • includes at least two groups, one of which does not receive the experimental treatment

  • includes at least two groups, one differing from the other by two or more variables

Explicación

Pregunta 79 de 100

1

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that _____.

Selecciona una de las siguientes respuestas posibles:

  • a blending of traits has occurred

  • each offspring has the same alleles for each of two different traits

  • the parents were true-breeding for contrasting traits

  • the particular trait shows incomplete dominance

  • the parents were both heterozygous for the particular trait

Explicación

Pregunta 80 de 100

1

Which of the following does NOT occur during mitosis?

Selecciona una de las siguientes respuestas posibles:

  • separation of the spindle poles

  • condensation of the chromosomes

  • spindle formation

  • replication of the DNA

  • separation of sister chromatids

Explicación

Pregunta 81 de 100

1

In the cells of some organisms, mitosis occurs without cytokinesis. This results in _____.

Selecciona una de las siguientes respuestas posibles:

  • cells with more than one nucleus

  • destruction of chromosomes

  • cells that are unusually small

  • cell cycles lacking an S phase

  • cells lacking nuclei

Explicación

Pregunta 82 de 100

1

DNA double helices are soluble in water but insoluble in alcohol. How do these physical properties reflect the chemical structure of the DNA molecule?

Selecciona una de las siguientes respuestas posibles:

  • The 5 prime to 3 prime polarity of DNA makes it soluble in water but not in alcohol.

  • The purine and pyrimidine bases are hydrophilic.

  • The charged phosphate groups and sugars of DNA are hydrophilic.

  • The charged R-groups of DNA are hydrophilic.

Explicación

Pregunta 83 de 100

1

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Selecciona una de las siguientes respuestas posibles:

  • Codons are a nearly universal language among all organisms.

  • Prokaryotic codons usually specify different amino acids than those of eukaryotes.

  • The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes.

  • Prokaryotic codons usually contain different bases than those of eukaryotes.

Explicación

Pregunta 84 de 100

1

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?

Selecciona una de las siguientes respuestas posibles:

  • synthesis of chromatids

  • formation of telophase nuclei

  • spindle fiber formation

  • cell membrane synthesis

  • nuclear envelope breakdown

Explicación

Pregunta 85 de 100

1

Franklin and Wilkins analyzed DNA by bombarding DNA crystals with X-rays. Their analysis yielded two numbers that sparked interest, 3.4 nm and 0.34 nm. What is the significance of these numbers?

Selecciona una de las siguientes respuestas posibles:

  • The width of a DNA molecule is 3.4 nm, whereas the width of a nucleotide monomer is 0.34 m.

  • The 10 to 1 ratio signifies that DNA molecules are ten times longer than they are wide.

  • DNA molecules are 3.4 nm long and 0.34 nm wide.

  • It turned out to be just a coincidence.

  • These numbers tell us there are ten rungs, or steps, on the DNA "ladder" for every turn of the helix.

Explicación

Pregunta 86 de 100

1

A ribozyme is _____.

Selecciona una de las siguientes respuestas posibles:

  • an enzyme that synthesizes RNA as part of the transcription process

  • an RNA with catalytic activity

  • an enzyme that synthesizes RNA primers during DNA replication

  • an enzyme that catalyzes the association between the large and small ribosomal subunits

  • a catalyst that uses RNA as a substrate

Explicación

Pregunta 87 de 100

1

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

Selecciona una de las siguientes respuestas posibles:

  • metaphase

  • prometaphase

  • telophase

  • prophase

  • anaphase

Explicación

Pregunta 88 de 100

1

If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence _____.

Selecciona una de las siguientes respuestas posibles:

  • 5'UAACGU3'

  • 5'TGCAAT3'

  • 5'UGCAAU3'

  • 5'TAACGT3'

  • 3'UAACGU5'

Explicación

Pregunta 89 de 100

1

A typical natural population of guppies consists of hundreds of guppies. Which statement best describes the guppies of a single species in an isolated population?

Selecciona una de las siguientes respuestas posibles:

  • The guppies share all of the same characteristics and are identical to each other.

  • The guppies share all of the essential characteristics of the species; the minor variations they display don’t affect survival.

  • The guppies are all identical on the inside, but have many differences in appearance.

  • The guppies share many essential characteristics, but also vary in many features.

Explicación

Pregunta 90 de 100

1

Fitness is a term often used by biologists to explain the evolutionary success of certain organisms. Which feature would a biologist consider to be most important in determining which guppies were the “most fit”?

Selecciona una de las siguientes respuestas posibles:

  • large body size and ability to swim quickly away from predators

  • excellent ability to compete for food

  • high number of offspring that survived to reproductive age

  • high number of matings with many different females.

Explicación

Pregunta 91 de 100

1

Assuming ideal conditions with abundant food and space and no predators, what would happen if a pair of guppies were placed in a large pond?

Selecciona una de las siguientes respuestas posibles:

  • The guppy population would grow slowly, as guppies would have only the number of babies that are needed to replenish the population.

  • The guppy population would grow slowly at first, then would grow rapidly, and thousands of guppies would fill the pond.

  • The guppy population would never become very large, because only organisms such as insects and bacteria reproduce in that manner.

  • The guppy population would continue to grow slowly over time.

Explicación

Pregunta 92 de 100

1

Once a population of guppies has been established for a number of years in a real (not ideal) pond with other organisms including predators, what will likely happen to the population?

Selecciona una de las siguientes respuestas posibles:

  • The guppy population will stay about the same size.

  • The guppy population will continue to rapidly grow in size.

  • The guppy population will gradually decrease until no more guppies are left.

  • It is impossible to tell because populations do not follow patterns.

Explicación

Pregunta 93 de 100

1

In guppy populations, what are the primary changes that occur gradually over time?

Selecciona una de las siguientes respuestas posibles:

  • The traits of each individual guppy within a population gradually change.

  • The proportions of guppies having different traits within a population change.

  • Successful behaviors learned by certain guppies are passed on to offspring.

  • Mutations occur to meet the needs of the guppies as the environment changes.

Explicación

Pregunta 94 de 100

1

Lizards eat a variety of insects and plants. Which statement describes the availability of food for lizards on the Canary Islands?

Selecciona una de las siguientes respuestas posibles:

  • Finding food is not a problem since food is always in abundant supply.

  • Since lizards can eat a variety of foods, there is likely to be enough food for all of the lizards at all times.

  • Lizards can get by on very little food, so the food supply does not matter.

  • It is likely that sometimes there is enough food, but at other times there is not enough food for all of the lizards.

Explicación

Pregunta 95 de 100

1

What do you think happens among the lizards of a certain species when the food supply is limited?

Selecciona una de las siguientes respuestas posibles:

  • The lizards cooperate to find food and share what they find.

  • The lizards fight for the available food and the strongest lizards kill the weaker ones.

  • Genetic changes that would allow lizards to eat new food sources are likely to be induced.

  • The lizards least successful in the competition for food are likely to die of starvation and malnutrition.

Explicación

Pregunta 96 de 100

1

A well-established population of lizards is made up of hundreds of individual lizards. On an island, all lizards in a lizard population are likely to . . .

Selecciona una de las siguientes respuestas posibles:

  • be indistinguishable, since there is a lot of interbreeding in isolated populations.

  • be the same on the inside but display differences in their external features.

  • be similar, yet have some significant differences in their internal and external features.

  • be the same on the outside but display differences in their internal features.

Explicación

Pregunta 97 de 100

1

Which statement best describes how traits in lizards will be inherited by offspring?

Selecciona una de las siguientes respuestas posibles:

  • When parent lizards learn to catch particular insects, their offspring can inherit their specific insect-catching-skills.

  • When parent lizards develop stronger claws through repeated use in catching prey, their offspring can inherit their stronger-claw trait.

  • When parent lizards’ claws are underdeveloped because easy food sources are available, their offspring can inherit their weakened claws.

  • When a parent lizard is born with an extra finger on its claws, its offspring can inherit six-fingered claws.

Explicación

Pregunta 98 de 100

1

According to the theory of natural selection, where did the variations in body size in the three species of lizards most likely come from?

Selecciona una de las siguientes respuestas posibles:

  • The lizards needed to change in order to survive, so beneficial new traits developed.

  • The lizards wanted to become different in size, so beneficial new traits gradually appeared in the population.

  • Random genetic changes and sexual recombination both created new variations.

  • The island environment caused genetic changes in the lizards.

Explicación

Pregunta 99 de 100

1

Fitness is a term often used by biologists to explain the evolutionary success of certain organisms. Below are descriptions of four fictional female lizards. Which lizard might a biologist consider to be the “most fit”?

Selecciona una de las siguientes respuestas posibles:

  • lizard A

  • lizard B

  • lizard C

  • lizard D

Explicación

Pregunta 100 de 100

1

What could cause one species to change into three species over time?

Selecciona una de las siguientes respuestas posibles:

  • Groups of lizards encountered different island environments so the lizards needed to become new species with different traits in order to survive.

  • Groups of lizards must have been geographically isolated from other groups and random genetic changes must have accumulated in these lizard populations over time.

  • There may be minor variations, but all lizards are essentially alike and all are members of a single species.

  • In order to survive, different groups of lizards needed to adapt to the different islands, and so all organisms in each group gradually evolved to become a new lizard species.

Explicación

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