More quizzes

Question 1

1. 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 of the following statements is true about these genes?
   A. ACTB is homologous to ACTC1 but not to MreB.
   B. ACTB is orthologous to ACTC1 but not to MreB.
   C. ACTB is paralogous to ACTC1 but not to MreB.
   D. MreB is orthologous to ACTB but not to ACTC1.
   E. ACTB is paralogous to both ACTC1 and MreB.

Answer 1

c

Question 2

5. Histone subunits are modified to regulate transcription. There are also different variants of these histones subunits. What explanation most accurately explains the reason for variants?
   A. Changes such as methylation and acetylation effect the distance between nucleosomes.
   B. Methylation of histones over a large region creates heterochromatin forming structures such as the
   centromere.
   C. CENP-A substitutes for H3 which is important in centromere function and kinetochore assembly.
   D. H2A substitutes for H2B to regulate processes such as transcription.
   E. Non-histone proteins help stabilize the nucleosome and can be used as a substitution of a subunit.

Answer 2

c

Question 3

7. Imagine a segment of DNA (within a gene) encoding a certain amount of information in its nucleotide sequence. When this segment is fully transcribed into mRNA and then translated into protein, in general, …
   A. the protein sequence would carry more information compared to the DNA and mRNA sequences, because its alphabet has 20 letters.
   B. the protein sequence would carry less information compared to the DNA and mRNA sequences, because several codons can correspond to one amino acid.
   C. the amount of information in the mRNA sequence is lower, because the mRNA has been transcribed using only one of the DNA strands as the template.
   D. the amount of information in the mRNA sequence is higher, because several mRNA molecules can be transcribed from one DNA molecule.

Answer 3

b

Question 4

10. An elongating ribosome is bound to appropriate tRNAs in both the A and the P sites and is ready for peptidyl transfer. What happens next?
    A. The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA.
    B. The amino end of the polypeptide chain is released from the P-site tRNA and joined to the free carboxyl group of the amino acid linked to the A-site tRNA.
    C. The carboxyl end of the amino acid is released from the A-site tRNA and joined to the free amino group of the polypeptide chain linked to the P-site tRNA.
    D. The amino end of the amino acid is released from the A-site tRNA and joined to the free carboxyl group of the polypeptide chain linked to the P-site tRNA.

Answer 4

a

Question 5

16. Put the following statements about RNA processing in the proper order.

1) Internal A nucleotide attacks the 5’ end of the intron to form a lariat
2) U1 snRNP recognizes the 5’ splice sequence
3) After about 25 nucleotides are synthesized a 5’- guanine cap is added
4) RNApolymerasedisassociates
5) AAUAAA sequence is recognized by poly-A polymerase
6) BBP recognizes the internal branch point site
7) Poly-A binding proteins add the poly-A tail to the 3’ end

A. 3-2-6-1-4-5-7
B. 3-6-2-1-4-5-7
C. 3-2-6-1-5-4-7
D. 5-7-2-6-1-3-4
E. 5-7-6-2-1-3-4

Answer 5

c

Question 6

17. How does a eukaryotic cell deal with the superhelical tension in its genomic DNA resulting from the activity of RNA polymerases?
    A. DNA gyrase introduces negative supercoils, keeping the DNA under constant tension.
    B. The RNA polymerases are allowed to rotate freely around their templates during transcription, leading
    to the relaxation of the tension.
    C. DNA topoisomerases rapidly remove the superhelical tension caused by transcription.
    D. The nucleosomes adjust the tension by binding to positively supercoiled regions behind a moving RNA
    polymerase.
    E. All of the above.

Answer 6

c

Question 7

20. Comparing mRNA molecules from human and Escherichia coli cells, which of the following is typically NOT true?
    A. A human mRNA has a special 5’ cap, while a bacterial mRNA does not.
    B. A human mRNA has a poly-A tail, while a bacterial mRNA does not.
    C. A human mRNA undergoes alternative splicing, while a bacterial mRNA does not.
    D. A human mRNA contains noncoding sequences, while a bacterial mRNA does not.
    E. A typical human mRNA encodes one protein, while many bacterial mRNAs encode several different
    proteins.

Answer 7

d

Question 8

2. In contrast to transporters, the channel proteins in cellular membranes …
   A. interact strongly with the solute(s) that they transport.
   B. undergo a conformational change every time they transport a solute.
   C. can only mediate passive transport.
   D. form pores that are always open.

Answer 8

c

Question 9

3. Which method is used to control the expression of a specific gene at the level of translation?
A. histone actylation
B. 3' UTR binding proteins
C. alternative sigma factors
D. DNA methylation
E. eIF2 phosphorylation

Answer 9

b

Question 10

4. Which of the following is NOT correct regarding cholesterol?
   A. It is an amphiphilic molecule.
   B. It is a sterol.
   C. It makes the membrane less permeable to small hydrophilic molecules.
   D. It is found in membranes of virtually all living cells.
   E. It is concentrated in lipid rafts.

Answer 10

d

Question 11

6. Studying the expression of a transcription regulatory protein in two cell types, you have performed experiments showing that the mRNA encoding the protein is present at higher levels in the cytosol one of the cell types. Which of the following steps in expression of the gene encoding this protein is NOT likely to be differentially controlled in these cell types?
A. Translation
B. mRNAdegradation
C. mRNAtransport
D. Transcription

Answer 11

a

Question 12

7. Demethylation of GC-island in the promoter decrease gene expression.
   A. True
   B. False

Answer 12

b

Question 13

8. What determines the time and place that a certain gene is transcribed in the cell?
   A. The type of cis-regulatory sequences associated with it
   B. The relative position of cis-regulatory sequences associated with it
   C. The arrangement of various cis-regulatory sequences associated with it
   D. The specific combination of transcription regulators present in the nucleus
   E. All of the above

Answer 13

e

Question 14

9. Which of the following DNA-binding motifs uses β sheets to recognize DNA bases?
A. The helix-turn-helix motif
B. Theleucinezipper
C. The zinc finger motif
D. The helix-loop-helix motif
E. None of the above

Answer 14

e

Question 15

10. Transcription regulation has similarities and differences in bacteria and in eukaryotes. Which of the following is correct in this regard?
    A. DNA looping for gene regulation is the rule in bacteria but the exception in eukaryotes.
    B. Most bacterial genes are regulated individually, whereas most eukaryotic genes are regulated in
    clusters.
    C. Transcription regulators in both bacteria and eukaryotes usually bind directly to RNA
    polymerase.
    D. The rate of transcription for a eukaryotic gene can vary in a much wider range than for a bacterial
    gene
    E. The default state of both bacterial and eukaryotic genomes is transcriptionally active.

Answer 15

d

Question 16

13. The following schematic drawing represents the activation of transcription for a eukaryotic gene (gene X). Indicate which sequence correctly correlates the components (A to D) in the drawing to their name.
    A. A-TFIID transcription factor; B-“Spacer” DNA that may encode lncRNAs; D-Mediator
    B. B- cis-Regulatory sequence; C-“Spacer” DNA that may encode lncRNAs; D- trans-acting
    transcription factor
    C. A-TFIID transcription factor; B- cis-Regulatory sequence; D-Mediator
    D. A-TFIID transcription factor; B- cis-Regulatory sequence; D- trans-acting transcription factor

Answer 16

c

Question 17

14. Replacing arginine by tryptophan in the structure of a protein will have
    A. no effect, they are both basic
    B. a slight change in structure, they are of different sizes
    C. an effect due to a change to a nonpolar amino acid
    D. an effect only on function

Answer 17

c

Question 18

16. Transmembrane proteins …
    A. are typically exposed only to one side of the membrane.
    B. cannot contain α helices in the part of their structure that interacts with the membrane interior.
    C. are often further attached to the membrane via a GPI anchor.
    D. contain a hydrophobic region.
    E. cannot contain β sheets in the part of their structure that interacts with the membrane interior.

Answer 18

d

Question 19

1. Proteins including the sequence Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val are signal sequences meant for the following transport
   a. From the nucleus
   b. To the nucleus
   c. To the ER
   d. To the mitochondria

Answer 19

b

Question 20

1. Proteins targeted to the ER require the following sequence
   a. Met-Glu-Glu-Leu-Ser-Gln-Ala
   b. N terminus-Met-Leu-Ser-Leu-Arg-Gln
   c. Ser-Lys-Leu-C terminus
   d. N terminus-Met-Met-Ser-Phe-Val-Ser

Answer 20

d

Question 21

1. Which of the following encodes mitochondrial proteins?
   a. The nuclear genome
   b. The mitochondrial genome
   c. The chloroplast genome
   d. Only a and b

Answer 21

d

Question 22

1. Nascent polypeptides on ribosomes are recruited to the ER by which of the following mechanism(s)?
   a. SRP recognizes and binds to the signal sequence. Brings the entire complex to SRP receptors
   b. Signal recognition is mediated by the TAT pathway to initiate translocation
   c. Binding of Calnexin to the signal sequence on the nascent polypeptide
   d. Only b and c

Answer 22

a

Question 23

1. The antigen binding site in Antibodies is structurally formed by
   a. Hypervariable regions
   b. V segments
   c. D segments
   d. Constant regions

Answer 23

a

Question 24

1. Proteins may move from the nucleus to
   a. Just the cytoplasm
   b. The cytoplasm and mitochondria
   c. The cell membrane
   d. The peroxisome

Answer 24

a

Question 25

1. Proteins can move from the cytoplasm to
   a. The mitochondria
   b. The chloroplast
   c. The endoplasmic reticulum
   d. All of the above

Answer 25

d

Question 26

1. Proteins targeted to the ER require the following sequence
   a. Met-Glu-Glu-Leu-Ser-Gln-Ala
   b. N terminus-Met-Leu-Ser-Leu-Arg-Gln
   c. Ser-Lys-Leu-C terminus
   d. N terminus-Met-Met-Ser-Phe-Val-Ser

Answer 26

d

Question 27

To trace family relationships between distantly related organisms such as humans, algae, bacteria, and archaea, one should compare their genomes in regions …
A. that evolve rapidly.
B. that have a higher mutation rate.
C. that code for proteins.
D. where mutations are hardly tolerated.
E. where most mutations are selectively neutral.

Answer 27

d

Question 28

Laboratory strains of the model organism Escherichia coli that are resistant to antibiotics are very often used in research laboratories as well as in the biotechnology industry. If cultures of such bacteria were allowed to contaminate the environment uncontrollably, it is possible that at some point, pathogenic bacteria such as Neisseria meningitidis (which causes meningitis and can cause death, especially in children) could acquire the same antibiotic-resistance gene, causing a meningitis outbreak that is difficult to treat. In this scenario, which of the following mechanisms is a more likely source of the antibiotic-resistance gene in N. meningitidis?

A. Random new gene generation
B. Intragenic mutation
C. Gene duplication
D. DNA segment shuffling
E. Horizontal gene transfer

Answer 28

e

Question 29

Out of nearly 5000 protein-coding gene families, there is a set of nearly 300 conserved gene families that are found in species from all domains of life. When one looks at the general functions assigned to these gene families, it is found that …
A. the majority of them function in cell-to-cell signaling.
B. the majority of them are poorly characterized.
C. more than one-third of them are involved in translation or amino acid transport and metabolism.
D. more than one-half of the shared families are involved in DNA replication and transcription.
E. Nearly all of them are involved in energy production and carbohydrate metabolism.

Answer 29

c

Question 30

Which of the following structures is exclusively found in eukaryotic cells?
A. Plasma membrane
B. Cell wall
C. Chromosome
D. Ribosome
E. Lysosome

Answer 30

e

Question 31

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 the many genes that are required for DNA replication. What has happened to these genes?
A. They have been lost during evolution, since the organelles no longer rely on DNA replication.
B. The required genes are kept in the nucleus, but many have evolved by gene transfer from the organelle.
C. These genes have undergone mutations and have changed beyond recognition, but are still present in the organelle.
D. The organelles do not replicate their DNA; they import new DNA from the nucleus.
E. The required genes are on plasmids that are separate from the organelle’s genome.
b

Answer 31

b

Question 32

Which of the following groups of living organisms has the highest variation in haploid genome size?
A. Mammals
B. Fish
C. Fungi
D. Protozoa
E. Prokaryotes

Answer 32

d

Question 33

All cells in a multicellular organism have normally developed from a single cell and share the same genome, but can nevertheless be wildly different in their shape and function. What in the eukaryotic genome is responsible for this cell-type diversity?
A. The genes that encode transcription regulatory proteins
B. The regulatory sequences that control the expression of genes
C. The genes that code for molecules involved in receiving cellular signals
D. The genes that code for molecules involved in sending cellular signals to other cells
E. All of the above

Answer 33

e

Question 34

Indicate if each of the following descriptions matches RNA (R) or DNA (D). Your answer would be a five-letter string composed of letters R and D only, e.g. RDDRR.
( ) It is mainly found as a long, double-stranded molecule.
( ) It contains the sugar ribose.
( ) It normally contains the bases thymine, cytosine, adenine, and guanine.
( ) It can normally adopt distinctive folded shapes.
( ) It can be used as the template for protein synthesis.

Answer 34

DRDRR

Question 35

Indicate if each of the following descriptions matches messenger RNAs (M), ribosomal RNAs (R), or transfer RNAs (T). Your answer would be a four-letter string composed of letters M, R, and T only, e.g. RRRT.
( ) They contain codons.
( ) They contain anticodons.
( ) They are (covalently) attached to amino acids.

Answer 35

MTTR

Question 36

Indicate if each of the following statements is true (T) or false (F). Your answer would be a five-letter string composed of letters T and F only, e.g. FFTFF.
( ) Animals ultimately depend on bacteria for fixation of the atmospheric nitrogen.
( ) If one finds animals in an isolated ecosystem, there should be photosynthetic organisms in that ecosystem as well.
( ) Carbon fixation can be carried out by bacteria only.
( ) All eukaryotes are organotrophs.
( ) Compared to eukaryotic cells, prokaryotes show greater biochemical diversity

Answer 36

TFFFT

Question 37

Imagine two spherical cells, one of which is 5000 times larger in volume than the other. The smaller is a prokaryote, and the larger cell is a eukaryote with 20% of its volume confined in a spherical nucleus. If the diameter of the prokaryotic cell is 0.7 micrometers, what is the diameter of the nucleus in the eukaryotic cell in micrometers? Write down your answer as a number only.

Answer 37

7