Fund Cell Post Review

1. Living systems are incredibly diverse in size, shape, environment, and behavior. This wide variety of organisms can make it difficult to define a “living entity”. Which of the following can be described as the smallest living unit?
   a. DNA
   b. cell
   c. organelle
   d. protein
   e. nucleus

b. cell

2. Of the following descriptions of cells, which statement is NOT correct?
   a. Cells can vary enormously in appearance and function.
   b. A cell can be a unicellular organism or part of a multicellular organism.
   c. Different cells have different chemical makeups and carry out distinct and unique chemical reactions.
   d. All cells are believed to have evolved from a common ancestral cell.
   e. Cells are self replicating units.

c. Different cells have different chemical makeups and carry out distinct and unique chemical reactions.

4. Select the option that best completes the following statement:
   “Evolution is a process __.”
   a. that can be understood based on the principles of mutation, natural selection, and survival of the fittest.
   b. that results from repeated cycles of adaptation and selection over billions of years.
   c. by which presentday cells and cellular organisms likely arose from common ancestral cell(s).
   d. that requires hundreds of thousands of years of stochastic process.
   e. all of the above.

e. all of the above.

5. The following are differences between prokaryotic and eukaryotic cells EXCEPT
   a. The absence versus presence of mitochondria
   b. The absence versus presence of a distinct nucleus
   c. The absence versus presence of ribosomes
   d. The absence versus presence of lysosomes
   e. The absence versus presence of endoplasmic reticulum

c. The absence versus presence of ribosomes

6. Which of the following is NOT a function of the endoplasmic reticulum?
   a. Detoxification of drugs and xenobiotics
   b. Synthesis of membrane lipids
   c. Synthesis of various steroid hormones such as the glucocorticoids
   d. Sequesters and buffers intracellular Ca²⁺ concentration
   e. Clearance of aging and dysfunctional mitochondria

e. Clearance of aging and dysfunctional mitochondria

7. Which statement is NOT true about events/conclusions from studies during the mid 1800s surrounding the discovery of cells?
   a. Cells came to be known as the smallest universal building block of living organisms.
   b. Scientists concluded that new cells could form spontaneously from the remnants of ruptured cells.
   c. Light microscopy was essential in demonstrating the commonalities between plant and animal tissues.
   d. New cells arise from the growth and division of previously existing cells.
   e. Cells of a multicellular organism are architecturally and functionally similar to those of a unicellular organism.

7. b. Scientists concluded that new cells could form spontaneously from the remnants of ruptured cells.

8. Prokaryotic cells can evolve rapidly, which helps them quickly adapt to new food sources and develop resistance to antibiotics. Which option lists the three main characteristics that support rapid evolution of prokaryotic populations?
   a. Microscopic size, motile, anaerobic
   b. Aerobic, motile, rapid growth
   c. No organelles, cell wall, can exchange DNA
   d. Large population, rapid growth, can exchange DNA
   e. Cell wall, motility, sporulation

d. Large population, rapid growth, can exchange DNA

9. Some prokaryotes live by utilizing entirely inorganic materials. Which inorganic molecule would be the predominant building block for fats, sugars, and proteins?
   a. O₂
   b. N₂
   c. CO₂
   d. H₂
   e. H₂O

b. N₂

10. The following are differences between rough and smooth endoplasmic reticulum EXCEPT
    a. Rough ER has both an inner and outer membrane whereas smooth ER has a single membrane
    b. They are enriched in different cell types (e.g., muscle cells have abundant SER)
    c. They look different under the electron microscope
    d. They have distinct functions in cells
    e. Their prominence can vary among different cell types

10. a. Rough ER has both an inner and outer membrane whereas smooth ER has a single membrane

11. What unit of length would you use to measure a typical plant or animal cell without having too many zeros?
    a. centimeters
    b. nanometers
    c. millimeters
    d. micrometers
    e. angstroms

d. micrometers

12. Which eukaryotic organelle has both an outer and inner membrane?
    a. Endoplasmic reticulum
    b. Mitochondrion
    c. Lysosome
    d. Peroxisome
    e. Golgi apparatus

b. Mitochondrion

13. Mitochondria contain their own genome and divide independently, yet cannot function long when isolated because they are
    a. viruses
    b. parasites
    c. endosymbionts
    d. anaerobes
    e. aerobes

c. endosymbionts

14. Which choice BEST describes the role of the lysosome?
    a. Transport to the Golgi apparatus
    b. Clean up, recycling, and disposal of macromolecules
    c. Sorting of transport vesicles
    d. Storage of excess macromolecules
    e. Fatty acid catabolism

b. Clean up, recycling, and disposal of macromolecules

15. On average, eukaryotic cells are times longer and have times more volume than prokaryotic cells.
    a. 5; 100
    b. 10; 200
    c. 10; 100
    d. 10; 1000
    e. 1; 1000

d. 10; 1000

16. Which term describes capturing external materials inside vesicles and bringing them into the cell?
    a. Degradation
    b. Exocytosis
    c. Pinocytosis
    d. Endocytosis/phagocytosis
    e. Apoptosis

d. Endocytosis/phagocytosis

1. Chemical reactions in living systems occur in an __ environment.
   a. Optimal
   b. Organic
   c. Extracellular
   d. Aqueous
   e. Inorganic

d. Aqueous

2. . Carbon-14 differs from carbon-12 by having two additional

   a. electrons

   b. neutrons

   c. protons

   d. ions

   e. photons

b. neutrons

3. A covalent bond is formed by
   a. Sharing electrons
   b. Loss of electrons from both atoms
   c. Loss of a proton
   d. Transfer of electrons
   e. No change in electron shells

a. Sharing electrons

4. An ionic bond is formed by
   a. Sharing electrons
   b. Loss of electrons from both atoms
   c. Loss of a proton
   d. Transfer of electrons from one atom to another
   e. Gain of electrons by both atoms

d. Transfer of electrons from one atom to another

5. Double covalent bonds limit molecular geometry because they
   a. Create new electron shells
   b. Fuse atomic nuclei
   c. Change reactivity
   d. Limit rotation of bonded atoms
   e. Prevent additional bonds

d. Limit rotation of bonded atoms

6. pH is calculated as
   a. pH = −log₁₀[H⁺]
   b. pH = log₁₀[H⁺]
   c. pH = −log₂[H⁺]
   d. pH = −log₁₀[OH⁻]
   e. pH = log₁₀[OH⁻]

6. a. pH = −log₁₀[H⁺]

7. Which building block assembles selectively permeable boundaries?
   a. Sugars
   b. Fatty acids
   c. Amino acids
   d. Nucleotides
   e. ATP

b. Fatty acids

8. What force keeps nucleotide bases stacked in DNA/RNA?
   a. Hydrophobic interactions
   b. Hydrogen bonds
   c. Covalent bonds
   d. van der Waals forces
   e. Ionic bonds

a. Hydrophobic interactions

9. Possible RNA sequences of 100 nucleotides equals
   a. 100⁴
   b. 4¹⁰⁰
   c. 4 × 100
   d. 100/4
   e. 100

b. 4¹⁰⁰

10. Biological recognition mostly relies on
    a. Covalent bonding
    b. π–π interactions
    c. Non covalent interactions
    d. All of the above
    e. None of the above

c. Non covalent interactions

Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of

a. a water molecule

b. an amino group

c. a carbon atom

d. a carboxylic acid group

e. an OH group

a. a water molecule

The variations in the physical characteristics between different proteins are influenced by the overall amino acid compositions, but even more important is the unique amino acid

a. number

b. sequence

c. bond

d. orientation

e. charge

b. sequence

The primary structure of a protein is the

a. amino acid composition

b. amino acid sequence

c. average size of amino acid side chains

d. lowest energy conformation

e. charge property of the amino acid sequence

b. amino acid sequence

Common secondary protein structures such as α-helix and β-sheet structures are energetically favored because
a. they optimize main-chain hydrogen bonds
b. they represent all possible conformations
c. they maximize clashes between atoms
d. they minimize clashes between atoms
e. the peptide backbone is free to rotate

a. they optimize main-chain hydrogen bonds

Fully folded proteins typically have polar side chains on their surfaces, where electrostatic attractions and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in the solvent. In contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the following would NOT occur to accommodate an internal, polar side chain?
a. hydrogen bond between two polar side chains
b. hydrogen bond between polar side chain and backbone
c. hydrogen bond between polar side chain and aromatic side chain
d. hydrogen bonds involving a buried water molecule
e. no need for hydrogen bonding

A hydrogen bond forms between a polar side chain and an aromatic side chain

What is the effect of solvents used in protein denaturation?
a. break all covalent interactions
b. break all noncovalent interactions
c. break some noncovalent interactions, resulting in misfolding
d. create a new protein conformation
e. block charge–charge interactions

 b. break all noncovalent interactions

Which statement is TRUE?
a. peptide bonds are the only covalent bonds linking amino acids
b. free rotation around all backbone bonds
c. nonpolar amino acids tend to be in protein interiors
d. backbone atom sequence varies between proteins
e. polar amino acids are buried in the core

c. nonpolar amino acids tend to be in protein interiors

Protein folding can be studied using a solution of purified protein and a denaturant (urea), a solvent that interferes with noncovalent interactions. Which of the following is often observed after the denaturant is removed from the protein solution?
a. refolding to original conformation
b. remains denatured
c. aggregates and precipitates
d. folds into a new stable conformation
e. folds into different structures

a. refolding to original conformation

Which statement is FALSE about molecular chaperones?
a. They assist polypeptide folding by helping the folding process follow the most energetically favorable pathway.

b. They can isolate proteins from other components of the cells until folding is complete.

c. They can interact with unfolded polypeptides in a way that changes the final fold of the

protein.

d. They help streamline the protein-folding process by making it a more efficient and reliable process inside the cell.

e. The term chaperone implies that the entity assist in the process of protein folding but itself is not part of the reaction.

 c. change the final fold of the protein

Which activated carrier supports chaperone mediated folding?
a. FADH₂
b. ATP
c. NADPH
d. NADH
e. ADP

b. ATP

What visual model best displays protein secondary structure?
a. ribbon
b. spacefilling
c. backbone
d. wire
e. chemical structure

a. ribbon

Secondary structures are
a. regular, repeated motifs with favorable energy
b. temporary unstable conformations
c. sidechain interactions
d. chemical modifications
e. high

a. regular, repeated motifs with favorable energy

What stabilizes α-helices and β-sheets?
a. amino acid sequence
b. side-chain interactions
c. hydrophobic core
d. hydrogen bonds along the backbone
e. peptide bonds

d. hydrogen bonds along the backbone

Which is NOT a feature of α-helices?
a. left-handed helix
b. 3.6 amino acids per turn
c. cylindrical shape
d. side chains point outward
e. intra-chain hydrogen bonding

a. left-handed helix

The peptide bond cannot rotate because
a. it is covalent
b. it is noncovalent
c. rotation causes clashes
d. partial doublebond character
e. it is a single bond

d. partial double bond character

Which is NOT a feature of β-sheets?
a. antiparallel regions
b. coiled-coil patterns
c. extended backbone
d. parallel regions
e. helix-turn-helix

b. coiled-coil patterns

Stable wrapping of helices (e.g., collagen) is driven by
a. hydrophilic bonds
b. hydrophobic interactions
c. van der Waals
d. hydrogen bonds
e. ionic bonds

b. hydrophobic interactions

Which protein has a coiled-coil structure?
a. insulin
b. tropomyosin
c. myoglobin
d. porin
e. trypsin

tropomyosin

A protein domain is
a. small cluster of helices/sheets
b. substrate-binding pocket
c. multi-polypeptide complex
d. independently folding segment
e. catalytic pocket

d. independently folding segment

Which is NOT a fibrous protein?
a. myosin
b. collagen
c. α-keratin
d. elastin
e. crystallin

e. crystallin

Which globular protein forms hollow tubes in neurons?
a. tubulin
b. actin
c. keratin
d. collagen
e. intermediate filament

a. tubulin

Which statement about disulfide bonds is TRUE?
a. formed by methionine
b. mainly cytosolic
c. change final protein form
d. more common intracellularly
e. formed by cysteine crosslinking

e. formed by cysteine crosslinking

Ligand binding sites are typically located
a. flat protein surface
b. open pocket/cavity on surface
c. buried interior
d. formed only upon ligand binding
e. anywhere on surface

 b. open pocket/cavity on surface

1. In a DNA double helix,

a. the two DNA strands are identical.

b. purines pair with purines.

c. thymine pairs with cytosine.

d. the two DNA strands run antiparallel.

d. the two DNA strands run antiparallel.

Which of the following chemical groups is NOT used to construct a DNA molecule?

a. five-carbon sugar

b. phosphate

c. nitrogen-containing base

d. six-carbon sugar

d. six-carbon sugar

3. Which of the following structural characteristics is NOT normally observed in a DNA duplex?

a. purine–pyrimidine base pairs

b. helical sugar–phosphate backbone

c. uniform left-handed twist

d. antiparallel strands

c. uniform left-handed twist

4. Which of the following DNA strands can form a DNA duplex by complementary base pairing?

a. 5′-AAGCCGAA-3′

b. 5′-AAGCCGTT-3′

c. 5′-AAGCGCAA-3′

d. 5′-AAGCGCTT-3′

b. 5′-AAGCCGTT-3′

The DNA from two different species can often be distinguished by a difference in the

a. ratio of A + T to G + C.

b. ratio of A + G to C + T.

c. ratio of sugar to phosphate.

d. presence of bases other than A, G, C, and T.

a. ratio of A + T to G + C

The complete set of information in an organism’s DNA is called its

a. genetic code.

b. coding sequence.

c. gene.

d. genome.

d. genome.

7. The human genome is divided into linear segments and packaged into structures called

chromosomes. What is the total number of individual chromosomes found in each of the

somatic cells in your body?

a. 22

b. 23

c. 44

d. 46

d. 46

8. Which of the following questions would NOT be answered by using karyotyping?

a. Is the individual genetically female or male?

b. Do any of the chromosomes contain pieces that belong to other chromosomes?

c. Does the individual have an extra chromosome?

d. Do any chromosomes contain point mutations?

d. Do any chromosomes contain point mutations?

9. The classic “beads-on-a-string” structure is a decondensed chromatin structure produced experimentally. Which chromatin components are NOT retained in this structure?

a. linker histones

b. linker DNA

c. nucleosome core particles

d. core histones

a. linker histones

10. The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does NOT form part of the octameric core?

a. H4

b. H2A

c. H3

d. H1

d. H1

In the 1940s, proteins were thought to be the more likely molecules to house genetic

information. What was the primary reason that DNA was not originally believed to be the

genetic material?

a. DNA has a high density of negative charges.

b. Nucleotides were known to be a source of chemical energy for the cell.

c. Both protein and nucleic acids were found to be components of chromosomes.

d. DNA was found to contain only four different chemical building blocks

d. DNA was found to contain only four different chemical building blocks

You are a virologist interested in studying the evolution of viral genomes. You are studying two. newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion?

a. because single-stranded genomes always have a large percentage of purines

b. by using the formula of G + A = C + T for all dsDNA. The viral genome isolated does not

comply with this rule.

c. because double-stranded genomes have equal amounts of A and G

D.bc the compostion does not follow the chargaff rules of purine=pryimidne for dsDNA

e. Because single-stranded genomes have a lower rate of mutation as in viruses for their

pathogenicity.

D.bc the compostion does not follow the chargaff rules of purine=pryimidne for dsDNA

13. DNA polymerases are processive, which means that they remain tightly associated with the template strand while moving rapidly and adding nucleotides to the growing daughter strand. Which piece of the replication machinery accounts for this characteristic?

a. DNA helicase

b. the sliding clamp

c. single-strand DNA binding protein

d. DNA primase

b. the sliding clamp

Given the sequence of one strand of a DNA helix (below), provide the sequence of the

complementary strand and label the 5′ and 3′ ends. 5′-GCATTCGTGGGTAG-3′

3′-CGTAAGCACCCATC-5′

The process of DNA replication requires that each of the parental DNA strands be used as a __________ to produce a duplicate of the opposing strand.

a. catalyst

b. competitor

c. template

d. copy

c. template

16. Which of the following statements about proofreading during DNA replication is INCORRECT?

a. The exonuclease activity is in a different domain of the DNA polymerase domain.

b. The exonuclease activity cleaves DNA in the 5′-to-3′ direction.

c. The primary DNA proofreading activity occurs concomitantly with DNA strand synthesis

rather than after synthesis is completed.

d. If an incorrect base is added, it is “unpaired” before removal.

b. The exonuclease activity cleaves DNA in the 5′-to-3′ direction.

17. The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be “overwound” in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication?

a. Nothing needs to be done because the two strands will be separated after replication is

complete.

b. Topoisomerases break the covalent bonds of the backbone, allowing the local unwinding of

DNA ahead of the replication fork to relieve the strain.

c. Helicase works to physically separate the strands of double-stranded DNA from each other.

d. DNA repair enzymes remove torsional stress as they replace incorrectly paired bases

b. Topoisomerases break the covalent bonds of the backbone, allowing the local unwinding of

18. Telomeres serve as caps protecting the ends of linear chromosomes. Which of the following is

FALSE regarding the replication of telomeric sequences?

a. The lagging-strand telomeres are not completely replicated by DNA polymerase.

b. Telomeres are made of repeating sequences.

c. Additional repeated sequences are added to the template strand.

d. The leading strand doubles back on itself to form a primer for the lagging strand.

d. The leading strand doubles back on itself to form a primer for the lagging strand

When double-stranded DNA is heated, the two strands separate into single strands in a process called melting or denaturation. The temperature at which half of the duplex DNA molecules are intact and half have melted is defined as the Tm (melting temperature). Questions:

A. Do you think Tm is a constant, or can it depend on other small molecules in the solution? Do

you think high salt concentrations increase, decrease, or have no effect on Tm?

B. Under standard conditions, the expected melting temperature in degrees Celsius can be

calculated from the equation Tm = 59.9 + [0.41 × %(G + C)] − (675/length of duplex). Does

the Tm increase or decrease if there are more G + C (and thus fewer A + T) base pairs? Does

the Tm increase or decrease as the length of DNA increases? Why?

C. Calculate the predicted Tm for a stretch of double helix that is 100 nucleotides long and

contains 50% G + C content?

Explanation (answer) for Q19:

Tm = 59.9 + [0.41 × %(G + C)] − (675/length of duplex).

• 59.9: A constant value that represents the baseline melting temperature.

• 0.41 × %(G + C): This term accounts for the influence of GC content on melting

temperature; GC base pairs have stronger hydrogen bonds than AT base pairs, so a

higher GC content leads to a higher melting temperature.

• 675/length of duplex: This term adjusts the melting temperature based on the length of

the DNA molecule; shorter DNA strands have a lower melting temperature.

For a DNA stretch that is 100 bp long with a 50% G + C content, we can calculate the Tm using

the given formula: Tm = 59.9 + 0.41 * 50 - 675/100. This simplifies to Tm = 59.9 + 20.5 - 6.75

= 73.65°C. Therefore, the predicted Tm for this particular DNA sequence is approximately

73.65°C.

20. The 4 nucleotide building blocks of DNA are aromatic “nitrogenous” base. What is the principal force

that keeps the base stacked in the interior of the DNA sugar-phosphate backbone and shielded from

solvent?

a. pi-pi bond interaction of juxtaposed nitrogenous bases

b. hydrogen bonding

c. covalent bonding

d. van der Waals interactions

e. charge-charge interaction

pi-pi bond interaction of juxtaposed nitrogenous bases

1. The repair of mismatched base pairs or damaged nucleotides in a DNA strand requires a multistep process. Which choice below describes the known sequence of events in this

process?

a. DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by repair proteins, the gap is filled by DNA polymerase, and the strand is sealed by DNA ligase.

b. DNA repair polymerase simultaneously removes bases ahead of it and polymerizes the correct sequence behind it as it moves along the template. DNA ligase seals the nicks in the repaired strand.

c. DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by an exonuclease, and the gap is repaired by DNA ligase.

d. A nick in the DNA is recognized, DNA repair proteins switch out the wrong base and

insert the correct base, and DNA ligase seals the nick.

a. DNA damage is recognized, the newly synthesized strand is identified by an existing nick in the backbone, a segment of the new strand is removed by repair proteins, the gap is filled by DNA polymerase, and the strand is sealed by DNA ligase.

Human beings with the inherited disease xeroderma pigmentosum have serious problems

with lesions on their skin and often develop skin cancer with repeated exposure to

sunlight. What type of DNA damage is not being recognized in the cells of these

individuals?

a. chemical damage

b. X-ray irradiation damage

c. mismatched bases

d. ultraviolet irradiation cross-linked all bases in DNA.

e. UV irradiation cross-link adjacent thymine bases into forming thymine dimer that hinders

DNA synthesis.

e. UV irradiation cross-link adjacent thymine bases into forming thymine dimer that hinders

DNA synthesis.

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not

giving the repair system enough time to correct the error before the DNA is duplicated.

This gives rise to mutation. If the cytosine in the sequence TCAT is deaminated and not

repaired, which of the following is the point mutation you would observe after this

segment has undergone two rounds of DNA replication?

a. TTAT

b. TUAT

c. TGAT

d. TAAT

e. TCAT

TTAT

Transcription is similar to DNA replication in that

a. an RNA transcript is synthesized discontinuously and the pieces are then joined together.

b. it uses the same enzyme as that used to synthesize RNA primers during DNA replication.

c. the newly synthesized RNA remains paired to the template DNA.

d. nucleotide polymerization of both DNA and RNA proceeds in the 5′-to-3′ direction.

d. nucleotide polymerization of both DNA and RNA proceeds in the 5′-to-3′ direction.

. Which of the following statements is FALSE?

a. A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule’s synthesis is completed.

b. If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies.

c. RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides.

d. Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.

d. Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.

7. Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because RNA

a. contains uracil and uses ribose as the sugar.

b. bases cannot form hydrogen bonds with each other.

c. nucleotides use a different chemical linkage between adjacent nucleotides as compared to DNA.

d. is single-stranded

d. is single-stranded

Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing?

a. 5′-CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′

b. 5′-UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3′

c. 5′-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3′

d. 5′-GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′

d. 5′-GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′

9. Which of the following statements is FALSE?

a. RNA polymerase can start making a new RNA molecule without a primer; DNA polymerase cannot.

b. RNA polymerase does not proofread its work; DNA polymerase does.

c. RNA polymerase catalyzes the linkage of ribonucleotides while DNA polymerase catalyzes the linkage of deoxyribonucleotides.

d. RNA polymerase adds bases in a 3′-to-5′ direction; DNA polymerase adds bases in a 5′-to-3′ direction.

d. RNA polymerase adds bases in a 3′-to-5′ direction; DNA polymerase adds bases in a 5′-to-3′ direction.

10. Transcription in bacteria differs from transcription in a eukaryotic cell because

a. RNA polymerase (along with its sigma subunit) can initiate transcription on its own.

b. RNA polymerase (along with its sigma subunit) requires the general transcription factors to assemble at the promoter before polymerase can begin transcription.

c. the sigma subunit must associate with the appropriate type of RNA polymerase to produce mRNAs.

d. RNA polymerase must be phosphorylated at its C-terminal tail for transcription to proceed.

a. RNA polymerase (along with its sigma subunit) can initiate transcription on its own.

11. Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

a. The ribosome binds to the mRNA.

b. The mRNA is polyadenylated at its 3′ end.

c. A guanine nucleotide with a methyl group is added to the 5′ end of the mRNA.

d. RNA polymerase dissociates.

a. The ribosome binds to the mRNA.

Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5′-TTTTTTTTTTTTTTTTTTTTTTTTT- 3′ has been covalently attached. After a short incubation, the beads are then extracted from the mixture. When you analyze thecellular nucleic acids that have stuck to the beads, which of the following is most abundant?

a. DNA

b. tRNA

c. rRNA

d. mRNA

d. mRNA

13. Which of the following statements about the genetic code is CORRECT?

a. All codons specify more than one amino acid.

b. The genetic code is redundant.

c. All amino acids are specified by more than one codon.

d. All codons specify an amino acid.

b. The genetic code is redundan

14. In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by

a. binding directly to a ribosome-binding site preceding the initiation codon.

b. scanning along the mRNA from the 5′ end.

c. recognizing an AUG codon as the start of translation.

d. binding an initiator tRNA

b. scanning along the mRNA from the 5′ end.

5. Which of the following statements about prokaryotic mRNA molecules is FALSE?

a. A single prokaryotic mRNA molecule can be translated into several proteins.

b. Ribosomes must bind to the 5′ cap before initiating translation.

c. mRNAs are not polyadenylated.

d. Ribosomes can start translating an mRNA molecule before transcription is compl

b. Ribosomes must bind to the 5′ cap before initiating translation.

16. Which of the following molecules is thought to have arisen first during evolution?

a. protein

b. DNA

c. RNA

d. All came to be at the same time.

c. RNA

17. According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a

a. molecule that could provide a template for the production of a complementary molecule.

b. double-stranded DNA helix.

c. molecule that could direct protein synthesis.

d. molecule that could catalyze its own replication.

d. molecule that could catalyze its own replication.

8. You are studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus?

a. high-energy

b. phosphate groups

b. RNA

c. lipids

d. carbohydrates

b. phosphate groups

19. When using a repeating trinucleotide sequence (such as 5′-AAC-3′) in a cell-free

translation system, you will obtain

a. three different types of peptides, each made up of a single amino acid.

b. peptides made up of three different amino acids in random order.

c. peptides made up of three different amino acids, each alternating with other in a repetitive

fashion.

d. poly-asparagine, as the codon for asparagine is AAC.

a. three different types of peptides, each made up of a single amino acid.

20. Imagine that an RNA polymerase is transcribing a segment of DNA that contains the following

sequence:

5′-AGTCTAGGCACTGA-3′

3′-TCAGATCCGTGACT-5

Top strand:

5′-AGTCTAGGCACTGA-3′

Bottom strand:

3′-TCAGATCCGTGACT-5′