Studied by 89 people
what enzyme is depicted in the following schematic drawing?
RNA polymerase
which of the following is true regarding genomic imprinting?
it is an epigenetic phenomenon
Insulin is a secretory protein made by the β cells in the pancreas. All but one of the following statements about insulin are true. Which statement is false?
Insulin undergoes secretion before proteolytic cleavage.
Which of the following are recognized by pattern recognition receptors as pathogen-associated molecular patterns?
Bacterial flagella components
How do multienzyme complexes in the cell, such as the fatty acid synthase, enhance reaction rates?
By allowing the channeling of pathway intermediates from one enzyme to the next
In the secondary structure of a DNA double helix, a purine (A or G) always base pairs with a pyrimidine (T or C). Why is this base-pair alignment critical to the structure of DNA?
pairing a purine with a pyrimidine ensures that the distance between the backbone strand is constant
In what way is Complex II similar to Complex I in the electron transport chain?
it donates electrons, reducing ubiquinone to ubiquinol
Below are different mobile genetic elements that are found in our genome. Which type appears to still be active and move in our genome, accounting for a detectable fraction of human mutations?
Nonretroviral retrotransposons
what would most reliably suggest that a genomic sequence is functionally important?
Multispecies conservation of the sequence
Type I topoisomerases enzymatically act to nick the DNA backbone to relieve accumulated strain. What is the role of tyrosin in this mechanism at the enzyme’s active site?
Covalently binding to a DNA phosphate group
which of the following is not a function for intrinsically disordered protein sequences?
holding a substrate in a specific conformation
DNA glycosylases constitute an enzyme family found in all three domains of life. What is the function of this battery of enzymes?
remove a purine or pyrimidine base from DNA
the production of new organelles requires the DNA that encodes the organelle specific proteins and what else
preexisting protein translocators
Comparing mRNA molecules from Human and Escherichia coli cells, which of the following is typically NOT true?
a human RNA contains noncoding sequences, while a bacterial mRNA does not
which of the following pairs of amino acid residues would you expect to from ionic bonds?
lysine and glutamic acid
the human gut microbiota is best described as what?
the community of microbes that live in gastrointestinal tract
what is a trait of the telomerase enzyme in human cells?
it has an RNA component
the observation that proteins often renature into their original conformations after they have been unfolded by denaturing solvents implies what?
the information needed to specify the three-dimensional shape of a protein is encoded in its amino acid sequence
which description applies to organelle genomes?
They may have lost some genes to the nuclear genome and retained others, in what may be an ongoing evolutionary process
Comparing the genomes of present-day mitochondria or chloroplasts with the genomes of their corresponding bacteria reveals that these organelles do not have many of the genes that are essential for their function. For instance, they lack many genes that are acquired for DNA replication. What has happened to these genes?
the required genes are kept in the nucleus, but many have evolved by gene transfer from the organelle
on average, errors occur in DNA synthesis only once in every 10 billion nucleotides incorporated. Which of the following does NOT contribute to this high fidelity of DNA synthesis?
Exonucleolytic proofreading by the 5’-to-3’ exonuclease activity for the enzyme to correct mispairing even after monomer incorporation/Priming by primase
several mechanisms contribute to the diversity of the mRNAs and proteins encoded by a single gene in our genome. Which of the following is normally NOT one of them?
Alternative choice of the reading frames
which statement regarding retroviral-like retrotransposons is true?
they have directly repeated long terminal repeats at their two ends when integrated into chromosomal DNA
what is NOT true about ethylene siganlling?
ethylene receptor autophosphorylates to mediate the signal
the chromatin remodeling complexes play an important role in chromatin regulation in the nucleus. The ability of these complexes to remodel the chromatin structure is dependent on which enzymatic function?
they have ATPase activity
what would you NOT expect to find in a bacterial cell?
ATP production in mitochondria
This model organism is used to study various eukaryotic cell and developmental processes such as cell division and cell death. Its hermaphrodite adult is composed of exactly 959 somatic (non-germ) cells, the lineage of each of which has been worked out with great precision. It is approximately 1 mm long. What is the best description of this organism?
It can be frozen indefinitely in a state of suspended animation.
Which of the following is a functional cellular link between innate and adaptative immunity?
Dendritic cell
An amino acid residue that is not part of the active site of an enzyme and does not interact with the ligand is nevertheless critical for ligand binding and is highly conserved. How can this be explained?
All the answers are correct:
The residue can help with restricting the access of water to the ligand-
binding site.
They behave like a liquid.
This residue can be critical for the correct folding and the placement of
ligand-binding site residues.
This residue can affect the chemical properties of the residues in the
ligand-binding site.
Transcriptional regulators, coactivators, and co-repressors are held in loose proximity with weak interactions as small, biomolecular condensates. What effect does this have?
Making transcription initiation an efficient and dynamic process
What is NOT true of all cells?
They use RNA as a template for genomic DNA polymerization.
How does Helicobacter pylori persist in the hostile environment of the stomach?
By producing the enzyme urease, which locally neutralizes the gastric acid
A protein is covalently attached to glycosylphosphatidylinositol. Which of the following is typically NOT true regarding this protein?
The protein is likely to be an ER resident, helping with the folding of nascent imported proteins.
Consider a human cell such as a hepatocyte. Which of the following
compartments occupies a larger volume in the cell?
Cytosol
Regarding the fusion and fission of mitochondria, which statement is NOT correct?
They both proceed in a single step in which both outer and inner membranes are fused or severed.
Which of the following processes is topologically similar to the formation of intralumenal vesicles in multivesicular bodies?
cytokinesis
Which of the following pathways does NOT directly deliver materials to lysosomes?
Exocytosis
Which statement about a virus is true?
It can act as a vector for gene transfer
As an mRNA molecule is processed in the nucleus, it loses some proteins and binds to new ones, some of which are used in mRNA surveillance pathways. The presence of which of the following molecules on an mRNA is a signal that the mRNA is still NOT ready for nuclear export?
snRNPs used in splicing
What is the main source of the free energy for the mechanical work performed by DNA helicases during DNA replication in our cells?
ATP hydrolysis by the helicase
The specific transfer RNA used for the incorporation of selenocysteine in proteins recognizes the UGA codon, which is normally a translation stop codon. What prevents this tRNA from reading through all the other “legitimate” UGA stop codons in the cells and causing a massive, disastrous recoding?
The mRNAs encoding the selenocysteine-containing proteins also contain additional sequences required for the recoding event.
In the following schematic diagram depicting the formation of vesicular tubular clusters between the endoplasmic reticulum (ER) and the cis Golgi network, what major coat proteins are indicated by 1 and 2, respectively?
COPII; COPI
Gene duplication can give rise to homologous genes that are part of gene families. For example, there are six actin genes in the genome of most mammalian species. In humans, the ACTB gene, which encodes a cytoskeletal actin, is expressed ubiquitously, while ACTC1 is expressed mainly in cardiac cells. Although bacteria lack the eukaryotic cytoskeletal organization, the bacterial MreB gene bears recognizable sequence similarity to mammalian actin genes and codes for a protein that is similar to actin in structure and function. Which statement about these genes is true?
ACTB is paralogous to ACTC1 but not to MreB.
This protein is present at every replication fork and prevents DNA polymerase from dissociating, but does not impede the rapid movement of the enzyme. Which statement regarding this protein is true regarding?
Its assembly normally follows the synthesis of a new primer by the DNA primase.
Which of the following is true of ALL protein structures?
They are all dynamic due to thermal energy
Protein subunits that interact specifically with DNA sequences…
do so via hydrogen bonds, ionic bonds, and hydrophobic interactions
Of the following proteins or protein complexes, which one does NOT typically interact with an elongating RNA polymerase II?
Mediator complexes
Which of the following better describes cross-presentation of protein antigens by professional antigen-presenting cells to naïve Tc cells?
Presentation of extracellular antigens by class I MHC proteins
Each chromosome in a human eukaryotic cell is composed of how many independent strands of DNA?
1
What is the major way by which the monomeric G protein Ras is activated in receptor tyrosine kinase signaling?
Activation of Ras-GEF
Phosphoinositides mark different cellular membranes and play key roles in protein trafficking inside the cell. Among them, PI(4,5)P is involved in receptor-mediated endocytosis as well as phagocytosis. Which statement about this particular phosphoinositide is NOT true?
It possesses a total of two phosphate groups.
Which of the following descriptions better applies to the cisternal maturation model rather than the vesicle transport model for the organization of the Golgi apparatus?
A cis Golgi cisterna becomes a medial cisterna which becomes a trans cisterna.
In mammals, mitochondrial gene inheritance can be described by all of the following, except which statement?
Usually they are biparentally inherited.
Which of the following correlates the best with biological complexity in eukaryotes?
Number of genes
Which group of living organisms has the highest variation in haploid genome size?
Protozoa
The eukaryotic chromosomes are organized inside the nucleus with a huge compaction ratio of several thousand-fold and is further accentuated during the mitotic cycle. What interaction is responsible for such a tight packaging?
The various histone proteins that wrap and fold the DNA
What is NOT a purpose of the 27 proteins produced by the SARS-CoV-2 genome?
Decreasing the host cell’s oxygen supply
Which statement is NOT true about bacteriophages?
They have no effect on the earth’s ecology.
What does phosphorylation of a protein by a protein kinase do?
It can create a binding site for other proteins.
Which of the following processes that happens inside of a cell does
NOT normally require consumption of free energy by the cell?
Diffusion of small molecules within the cell
Where do T cells develop?
Thymus
Which statement regarding Escherichia coli is true?
E. coli strain K-12 encodes about 4300 proteins.
Which genes are transcribed in the nucleoli within the eukaryotic nucleus?
rRNA
A replication fork is shown schematically below. The strand labeled A is
called the __________________ strand.
Lagging
In assembling a nucleosome, normally specific histone dimers first combine to form a tetramer, which then further combines with two of another type of histone dimers to form the octamer. Name these two histone dimers in order of how they combine.
H3–H4; H2A–H2B
The nuclear DNA polymerases in human cells have which trait?
They are unable to initiate polymerization de novo (i.e., in the absence of a primer).
In a plant’s life cycle, hormones play a critical role in the regulation of growth and behavioral processes. Which of the following hormones function in phototropism and gravitropism?
Auxin
Which of the following is NOT true of intrinsically disordered regions in proteins?
They are relatively rare to find in proteins.
Which of the following is NOT true regarding the members of a protein family in general?
They can functionally replace each other.
How is tRNA splicing different from mRNA splicing in eukaryotic cells?
All the answers are correct:
tRNA splicing involves RNA endonuclease and RNA ligase activities.
tRNA splicing does not create a lariat intermediate.
tRNA splicing does not proceed via transesterification reactions.
tRNA splicing is carried out by proteins only.
Many macromolecular complexes in the cell contain scaffold proteins. Which of the following is NOT something that these proteins do to benefit the cell?
They can replace the phospholipid bilayer in the plasma membrane.
What is NOT true regarding the tree of life?
Archaeal species were thought to belong to the eukaryotic world before sequence analysis placed them in a separate domain of life.
Which repair pathway can accurately repair a double-strand break?
Homologous recombination
DNA and RNA polymerase differ in all of the following except which of the following?
The type of chemical reaction they catalyze.
Which region of RNA Polymerase II is phosphorylated repeatedly, allowing it to recruit RNA processing machinery to the emerging transcript?
C-terminal domain
What is true about carbon and nitrogen from the environment?
They must be fixed into organic molecules to be utilized by cells.
The majority of transcription regulators make sequence-specific contacts with DNA in the major groove. In the two diagrams below, where are the contact surfaces that are exposed in the major groove?
1, 4
Which feature of DNA underlies its simple replication procedure?
The complementary relationship in the double helix
Mitochondria and chloroplasts are thought to have evolved from free- living aerobic bacteria that were engulfed by an ancestral anaerobic cell and established a mutually beneficial (symbiotic) relationship with it. Which statement about these organelles is NOT true?
they are found in all eukaryotes
Stimulated B lymphocytes switch from the synthesis of membrane- bound to secreted antibody molecules by increasing the concentration of a subunit of the trimeric CstF complex that cleaves and polyadenylates mRNAs. How does this up-regulation of CstF bring about the production of soluble antibodies?
It activates a weak polyadenylation site in the immunoglobulin primary transcript and prevents splicing, creating a shorter molecule that is secreted.
This model organism is particularly well suited for studying developmental processes in higher animals. It develops from a fertilized egg to an adult in only two to three months, and its body is transparent for the first two weeks, making it easy to observe cell behavior during development. What is NOT a characteristic that describes this organism?
It can fly
What do the enzymes topoisomerase I and topoisomerase II have in common?
They both have nuclease activity.
In meiosis, a crossover in one position is thought to inhibit crossing
over in the neighboring regions. This regulatory mechanism does what?
Ensures that even small chromosomes undergo at least one crossover
Why do viruses support the “RNA world” hypothesis of how life
originated?
The smallest viruses contain only a single-stranded RNA molecule.
All but one of the following are functions and/or characteristics of plant vacuoles. Which of the following is NOT consistent with these organelles?
They comprise a relatively small proportion of the cell’s volume.
Which cell type is NOT phagocytic?
Lymphocyte
All but one of the following factors are required for sorting proteins like lysosomal hydrolases to lysosomes (via endosomes). Which factor is NOT involved in this process?
COPI coat
What does NOT typically involve horizontal gene transfer?
The accidental duplication of a small region of a bacterial chromosome followed by cell division
Viruses are obligate parasites, which rely on a host for survival. Which of the following represents the correct order of events in the process of SARS CoV2 virus replication?
Entry, disassembly, replication, transcription, assembly, and release
A respiring mitochondrion will passively export to the cytoplasm which
of the following?
CO2
How does the genome of yeast typically compare to the human genome?
The yeast genome has a higher fraction of coding DNA.
Enzymes can catalyze cellular reactions through various mechanisms. Which of the following statements is NOT true regarding enzymes?
They accelerate a cellular reaction by destabilizing the transition state.
Mycobacterium tuberculosis can cause tuberculosis, a life-threatening lung infection, but can also infect an individual asymptomatically for years. It is not considered to be part of the normal flora and can infect healthy individuals upon exposure. It can only replicate in the host and thus mainly spreads by direct human contact. Mycobacterium tuberculosis is therefore what?
An obligate primary pathogen
Which statement regarding heterochromatin in a typical mammalian cell is true?
The different types of heterochromatin share an especially high degree of compaction.
Consider the proteins Ras, Src, and kinesin. Which of the following is NOT something they have in common?
They contain many repeating subunits to form a large protein complex.
Which of the following is NOT a common second messenger in cell signaling?
Tyrosine
What property of genome diversity accounts for a majority of the variation in genome size, even among related species?
The amount of noncoding DNA
What is true about lampbrush chromosomes?
They are thought to have a structure that is relevant to mammalian chromosomes in interphase.
Which network motif is the most prevalent way that transcriptional regulators ensure that daughter cells have cell memory so they become terminally differentiated?
Positive feedback loop
Which term best describes the endocytic process depicted in the schematic diagram below?
Macropinocytosis
Note 
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