Unit 1 Practice Questions
Describe how hypothesis and theories are different and how they relate to each other.
A hypothesis is a tentative statement about the natural world leading to predictions that can be tested. Theories may start as hypotheses, but they have been supported so many times, with so many different lines of evidence, and with no evidence refuting them, that we accept them as true explanations of the natural world.
Which of the following statements about theories is true? A. A theory can never be fully proven. B. A theory cannot be overturned by new results. C. A theory does not need to be further studied because it has already been figured out. D. A theory is not widely accepted by experts.
A). A theory can never be fully proven.
During the DNA replication stage, there is an enzyme called DNA helicase. The DNA helicase "unwinds" the molecule of double-stranded DNA. What is the purpose/job of the DNA helicase? A. DNA helicase breaks the hydrogen bonds between purines and pyrimidines B. DNA helicase breaks the covalent bonds between purines and pyrimidines C. DNA helicase breaks the covalent bonds of just pyrimidines. D. DNA helicase breaks the hydrogen bonds of just the purines.
A). DNA helicase breaks the hydrogen bonds between purines and pyrimidines
What does telomerase add? A. DNA to the 3' overhang. B. DNA to the 5' underhang. C. RNA to the 3' overhang. D. RNA to the 5' underhang.
A). DNA to the 3' overhang.
Which of the following shows the correct order in which proteins are used when replicating DNA? A. Helicase -> primase -> DNA polymerase III -> DNA polymerase I -> ligase B. Helicase -> primase -> DNA polymerase I -> DNA polymerase III -> ligase C. Helicase -> primase -> ligase -> DNA polymerase I -> DNA polymerase III D. Helicase -> ligase -> DNA polymerase III -> DNA polymerase I -> primase
A). Helicase -> primase -> DNA polymerase III -> DNA polymerase I -> ligase
What must this cell do before it can carry out mitosis? (The cell has a diploid number of 4 chromosomes; 2n = 4). A. Replicate its DNA B. Duplicate its centromeres C. Undergo cytokinesis D. A, B, and C
A). Replicate its DNA
About 20% of the drugs used as chemotherapeutics (cancer treatments) are nucleotide analogs. These chemotherapeutics are shaped like nucleotides but cannot be covalently linked to another nucleotide. During which phase of the cell cycle will these drugs exert their effect? A. S B. M C. G1 D. G2
A). S
If a 50-base-pair stretch of DNA is 15% thymine (T) & 15% adenine (A), then how many hydrogen bonds should hold the two strands together in this stretch of DNA? A. 115 B. 100 C. 150 D. 155 E. 160
B). 100
Because DNA structure involves base pairing (A pairs with T, C pairs with G), DNA with 38% A should have: A. 62% T B. 38% T, 12% G, 12% C C. 12% T, 25% G, 25% C D. 38% T; percentages of G and C cannot be determined
B). 38% T, 12% G, 12% C
If a cell has 1,000 pg (picograms) of nuclear DNA during G2, carried by 36 chromosomes, then how much DNA and how many chromosomes should there be in a single daughter nucleus after that cell undergoes mitosis? A) 500 pg; 18 chromosomes B) 500 pg; 36 chromosomes C) 250 pg; 18 chromosomes D) 250 pg; 36 chromosomes E) 250 pg; 9 chromosomes
B). 500 pg; 36 chromosomes
Which of the following is the correct order of events in mitosis? A. Nuclear envelope dissolves -> DNA condenses -> chromosome move to midline -> sister chromatids separate -> cytokinesis B. DNA condenses -> Nuclear envelope dissolves -> chromosome move to midline -> sister chromatids separate -> cytokinesis C. DNA condenses -> Nuclear envelope dissolves -> sister chromatids separate -> chromosome move to midline -> cytokinesis D. DNA condenses -> chromosome move to midline -> sister chromatids separate -> Nuclear envelope dissolves-> cytokinesis
B). DNA condenses -> Nuclear envelope dissolves -> chromosome move to midline -> sister chromatids separate -> cytokinesis
In a normally functioning cell, the cell cycle will be arrested at the G1 checkpoint until: A. The DNA is replicated B. Damaged DNA is repaired C. The protein p53 is produced D. Apoptosis occurs
B). Damaged DNA is repaired
HER2 codes for a protein receptor that promotes cell division in healthy breast tissue for growth and repair. A mutation to HER2 results in a gain-of-function by overamplification of the receptor protein. What is the term for the mutant HER2 gene and what is the result if one mutant gene introduced into a heathy cell with no previous HER2 mutations. A. Proto-oncogene; cancer B. Oncogene; cancer C. Tumor suppressor mutant; cancer D. Oncogene; no cancer E. Tumor suppressor mutant; no cancer
B). Oncogene; cancer
After a cell replicates its DNA, it often divides into two daughter cells. Each daughter cell receives a full set of the organism's DNA. What proportion of the DNA in each daughter cell is newly synthesized? A. The amount of newly synthesized DNA that each daughter cell receives is random. B. One half of the DNA in each daughter cell is newly replicated. C. All DNA in one new daughter cell is newly replicated, while none in the other is new. D. All the DNA in both daughter cells is newly replicated.
B). One half of the DNA in each daughter cell is newly replicated.
A research team at Columbia led by Minchen Chien and Jingyue Ju is studying the drug Sofosbuvir as a treatment for COVID-19. Sofosbuvir is a nucleotide analog that mimics the structure of Uracil. Here is a figure from their recent research paper published in 2020 in the Journal of Proteome Research. Compare the structure of Sofosbuvir to the structure of Uracil (left side of the figure). The difference in the phosphate groups prevents Sofosbuvir from creating bonds in that region. How would this affect Sofosbuvir's ability to interact with other nucleotides? A. Sofosbuvir would be able to engage in the same hydrogen AND covalent bonding as Uracil. B. Sofosbuvir would be able to engage in the same hydrogen bonding but NOT the same covalent bonding as Uracil C. Sofosbuvir would be able to engage in the same covalent bonding but NOT the same hydrogen bonding at Uracil D. Sofosbuvir would NOT be able to engage in the same covalent bonding nor hydrogen bonding as Uracil
B). Sofosbuvir would be able to engage in the same hydrogen bonding but NOT the same covalent bonding as Uracil
You observe that a cell trying to replicate its DNA failed and the DNA is twisted and knotted. Which enzyme most likely malfunctioned? A. Helicase B. Topoisomerase C. Primase D. DNA polymerase III
B). Topoisomerase
Which of the following is in the correct order in which events take place while replicating DNA? A. Unzip DNA -> make primer -> ligate DNA fragments -> replace primer -> add DNA nucleotides B. Unzip DNA -> make primer -> add DNA nucleotides -> replace primer -> ligate DNA fragments C. Unzip DNA -> add DNA nucleotides -> make primer -> replace primer -> ligate DNA fragments D. Unzip DNA -> copy leading strands -> copy lagging strands -> replace primer -> ligate DNA fragments
B). Unzip DNA -> make primer -> add DNA nucleotides -> replace primer -> ligate DNA fragments
Which of the following DNA sequences is complementary to this DNA sequence: 5'-AGCTATGCGGAT-3' A. 3'-ATCCGCATAGCT-5' B. 5'-AUCCGCAUAGCU-3' C. 5'-ATCCGCATAGCT-3' D. 5'-TCGATACGCCTA-3' E.5'-TAGGCGTATCGA-3'
C). 5'-ATCCGCATAGCT-3' ???
Which of the following statements about theories is true? A. A theory is a hypothesis that has been proven by many facts. B. A theory is a set of equations that describes many facts. C. A theory is an explanation for a related set of hypotheses that are supported by many facts. D. A theory is a hypothesis that hasn't been supported by facts yet.
C). A theory is an explanation for a related set of hypotheses that are supported by many facts.
A study by Thompson et al. (2022) investigated chromokinesin KIF2, which is a protein that is believed to be involved in chromosomal alignment during mitosis. Interestingly, researchers found that if the alpha-2 helices is mutated, the process of chromosome segregation is disrupted during mitosis, while chromosomal alignment is not disrupted as much. According to the results of this study, if someone had this mutation, which stage of mitosis would this affect the most and what would be a likely implication of this? a. Metaphase - increased cell proliferation and normal daughter cell structure b. Metaphase - decreased cell proliferation and normal daughter cell structure c. Anaphase - decreased cell proliferation and abnormal daughter cell structure d. Anaphase - increased cell proliferation and abnormal daughter cell structure' link to study: https://elifesciences.org/articles/78653
C). Anaphase - decreased cell proliferation and abnormal daughter cell structure
Recall the differences and characteristics of theory and hypotheses. Examine the following table and identify where "theory" and "hypothesis" are correctly identified. 1). Theory: Active learning involves constructing one's own knowledge and understanding of a concept. Hypothesis: Students who use active learning methods will outperform students who use passive learning methods on the final exam for BIOL 1403. 2). Theory: Students who use active learning methods will outperform students who use passive learning methods on the final exam for BIOL 1403. Hypothesis: Active learning involves constructing one's own knowledge and understanding of a concept. 3). Theory: Compared to non-sleep-deprived students, sleep-deprived students will have worse test performance on the final exam for BIOL 1403. Hypothesis: The main function of sleep is to conserve energy, to allow the body to repair itself and for the brain to undergo neural reorganization. 4). Theory: The main function of sleep is to conserve energy, to allow the body to repair itself and for the brain to undergo neural reorganization. Hypothesis: Compared to non-sleep-deprived students, sleep-deprived students will have worse test performance on the final exam for BIOL 1403. a. Only 1) b. Only 4) c. Both 1) and 4) d. Both 1) and 3)
C). Both 1) and 4)
Imagine a cell that has been exposed to a toxin that renders one of the DNA replication proteins inactive. This cell is unable to replicate its DNA because it is unable to unzip the stands of DNA. Which protein is inactive? A. Primase B. Ligase C. Helicase D. DNA polymerase I
C). Helicase
Why did the researchers choose to study a molecule that mimics Uracil rather than a different nucleotide? A. Uracil is not present naturally in human cells. B. Uracil is the most common nucleotide in the viral genome. C. Host (human) genome will be unaffected because uracil is not present in DNA. D. It did not matter which nucleotide they chose, it could have been any of them.
C). Host (human) genome will be unaffected because uracil is not present in DNA.
Nucleotides in the double strands of DNA interact with each other through: A. Covalent bonds B. Ionic bonds C. Hydrogen bonds D. The hydrophobic effect
C). Hydrogen bonds
For DNA replication to proceed, the following bonds must be disrupted: A. Covalent bonds between nucleotides B. Hydrogen bonds between the sugar and phosphate in each nucleotide C. Hydrogen bonds between nucleotides D. Covalent bonds between the sugar and the base in each nucleotide
C). Hydrogen bonds between nucleotides
Can we prove the Theory of Gravity? Explain. a.) Yes. Gravity can be observed, so it must be a fact. b.) Yes, but not yet, elite scientists are still working out the proof. c.) No. A theory can never be fully proven. d.) No. Gravity and constant acceleration are too similar.
C). No. A theory can never be fully proven.
Suppose a cell is exposed to a toxin that completely blocks DNA polymerase I but leaves the other DNA replication proteins unaffected. What effect would this have on DNA replication? A. The cell would synthesize leading strands but not lagging strands B. Replication would proceed as normal, but possibly slower C. The RNA primers would not be replaced with DNA D. The cell would successfully replicate its DNA, but there would be more mutations
C). The RNA primers would not be replaced with DNA
During genome replication, Sofosbuvir can be incorporated into RNA in place of Uracil. When it does, the next nucleotide cannot be added (right side of the figure). What would be the consequence of this? A. The human cell hosting the virus will undergo apoptosis (programmed cell death), killing the virus along with it B. Genome replication will proceed normally, but transcription and translation will fail, so the viral particles will die. C. The virus will be unable to replicate its genome so it will be unable to create more viral particles D.None of the above.
C). The virus will be unable to replicate its genome so it will be unable to create more viral particles
CELL CYCLE PHASES
CELL CYCLE PHASES
Which region(s) would engage in hydrogen bonding with a nucleotide in the complementary strand of DNA? A. The phosphate group B. The sugar C. The nucleic base D. A and B E. A, B, and C
D). A and B
Which of these bonds will be polar? A. C-H B. C-O C. O-H D. B and C E. A, B, and C
D). B and C
Why does the lagging stand consist of several short Okazaki fragments, as opposed to continuous DNA, replicated in long stretches? A. Because one side of each replication fork is longer than the other B. Because DNA polymerase III cannot synthesize long stretches of DNA C. Because polymerases synthesize DNA 5' to 3' on one strand and 3' to 5' on the other D. Because DNA polymerases can only move in one direction along a DNA strand
D). Because DNA polymerases can only move in one direction along a DNA strand
Which of the following is an example of a theory? a) While watching elephants in a grassland, you notice they use their trunks to bring water to their mouths to drink. b) Individuals evolve to meet the needs of the environment. c) If sunflowers listen to classic rock every evening, then they will have faster rates of growth than sunflowers who do not listen to classic rock. d) Evolution is based on a set of hypotheses that have been supported by evidence in numerous studies.
D). Evolution is based on a set of hypotheses that have been supported by evidence in numerous studies. (Explanation: a) Is incorrect because it is a fact or an observation. b) Is incorrect because it is a common misconception about the theory of evolution; individuals do not evolve. c) Is incorrect because it is an educated guess that is testable. This is known as a hypothesis. d) Is CORRECT! The theory of evolution has continually been proven and supported, but evidence has not been found to negate it.)
During which part of the eukaryotic cell cycle does the amount of DNA in the nucleus double? A) G0 B) M phase C) G1 phase D) S phase E) G2 phase
D). S phase
In a normally functioning cell, the cell cycle will be arrested at the G2 checkpoint until: A. The protein p53 is produced B. Apoptosis occurs C. Sister chromatids have separated D. The DNA is checked for correct replication
D). The DNA is checked for correct replication
A scientist conducts a well-designed experiment and analyzes the data. They find a statistically significant result and exclaim, "The data prove my hypothesis!" Assuming that there are no problems with the experimental design or analyses, which of the following statements best evaluates the scientist's claim? A. There is no problem with this statement because their results were statistically significant. B. This statement is problematic because data only prove theories. C. This statement is problematic because more than one study is needed to prove a hypothesis. D. This statement is problematic because a hypothesis can never be proven.
D). This statement is problematic because a hypothesis can never be proven.
A cell's nucleus contains 32 chromosomes during G1. The same cell should also contain 32 uncondensed, replicated chromosomes during which of the following mitotic stages? A. mid-metaphase B. G2 C. mid-anaphase D. early-prophase E. early-telophase
D). early-prophase
If mitosis occurs normally, but cytokinesis fails to occur subsequently, the result will be: A. two genetically identical nuclei, each within a different cell. B. two genetically different nuclei, each within a different cell. C. one nucleus with twice the normal number of chromosomes residing in a single cell. D. two genetically identical nuclei within a single cell. E. two genetically different nuclei within a single cell.
D). two genetically identical nuclei within a single cell.
If mitosis starts with a single mother cell, and if the subsequent cytokinesis fails to occur following successful, error-free mitosis, then the result will be A) two genetically identical nuclei, each within a different cell. B) two genetically different nuclei, each within a different cell. C) one nucleus with twice the normal number of chromosomes residing in a single cell. D) two genetically identical nuclei within a single cell. E) two genetically different nuclei within a single cell.
D). two genetically identical nuclei within a single cell.
DNA REPLICATION
DNA REPLICATION
DNA STRUCTURE
DNA STRUCTURE
Contrast how scientists use the word theory to how it is used in every-day language.
In every-day language, theory can often be used very casually to describe an idea or speculation. However, when scientists say "theory," they are referring to a hypothesis that has been supported extensively by many studies with no refuting evidence ever found. Scientists always acknowledge uncertainty, so they never say "prove," but theories are as close to "proven facts" as science can get.
MITOSIS
MITOSIS
NATURE OF SCIENCE
NATURE OF SCIENCE
Describe why a hypothesis can never be proven.
Scientists always acknowledge uncertainty, so they never say "prove." Scientists are always willing to update their understanding if data contradicts their pre-existing ideas or hypotheses.
Your friend poses the hypothesis that the purple people eater exists and has supernatural powers that make it impossible to detect. They argue that because you cannot prove that the purple people eater does not exist, it's a scientific fact that it does exist. Explain to your friend why their hypothesis cannot be evaluated using the scientific method.
The scientific method requires that a hypothesis can be tested and falsified. If an idea cannot be falsified, it is not a scientific hypothesis.
This patient is prescribed 5-fluorouracil, an anti-cancer drug that works by inhibiting thymidylate synthase, an enzyme that helps catalyze the production of thymidylate. Thymidylate is an important precursor for DNA biosynthesis. Another tumor biopsy is taken from this patient. What would be the main difference in the graph that indicates that the drug is working? a. 2) and 3) would be lower and smaller b. 2) and 3) would be higher and larger c. 1) would be much lower and smaller d. 1) would be much higher and larger
b. 2) and 3) would be higher and larger
