Practice Questions for Chapters 13 & 18
1) The role of a metabolite that controls a repressible operon is to
A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
B) bind to the operator region and block the attachment of RNA polymerase to the promoter.
C) increase the production of inactive repressor proteins.
D) bind to the repressor protein and inactivate it.
E) bind to the repressor protein and activate it.
Topic: Concept 18.1
Skill: Knowledge/Comprehension
2) The tryptophan operon is a repressible operon that is
A) permanently turned on.
B) turned on only when tryptophan is present in the growth medium.
C) turned off only when glucose is present in the growth medium.
D) turned on only when glucose is present in the growth medium.
E) turned off whenever tryptophan is added to the growth medium.
Topic: Concept 18.1
Skill: Knowledge/Comprehension
3) Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor
E) corepressor
Topic: Concept 18.1
Skill: Knowledge/Comprehension
4) A lack of which molecule would result in the cell's inability to "turn off" genes?
A) operon
B) inducer
C) promoter
D) ubiquitin
E) corepressor
Topic: Concept 18.1
Skill: Knowledge/Comprehension
5) Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer
binds to the operator?
A) ubiquitin
B) inducer
C) promoter
D) repressor
E) corepressor
Topic: Concept 18.1
Skill: Knowledge/Comprehension
6) Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its
conformation?
1
A) inducer
B) promoter
C) RNA polymerase
D) transcription factor
E) cAMP
Topic: Concept 18.1
Skill: Knowledge/Comprehension
7) A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in
A) continuous transcription of the structural gene controlled by that regulator.
B) complete inhibition of transcription of the structural gene controlled by that regulator.
C) irreversible binding of the repressor to the operator.
D) inactivation of RNA polymerase by alteration of its active site.
E) continuous translation of the mRNA because of alteration of its structure.
Topic: Concept 18.1
Skill: Application/Analysis
8) If you were to observe the activity of methylated DNA, you would expect it to
A) be replicating nearly continuously.
B) be unwinding in preparation for protein synthesis.
C) have turned off or slowed down the process of transcription.
D) be very actively transcribed and translated.
E) induce protein synthesis by not allowing repressors to bind to it.
Topic: Concept 18.2
Skill: Knowledge/Comprehension
9) The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to
an introduced double-stranded RNA is called
A) RNA interference.
B) RNA obstruction.
C) RNA blocking.
D) RNA targeting.
E) RNA disposal.
Topic: Concept 18.3
Skill: Knowledge/Comprehension
10) Which of the following best describes siRNA?
A) a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
B) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns
C) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
D) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
E) a molecule, known as Dicer, that can degrade other mRNA sequences
Topic: Concept 18.3
Skill: Knowledge/Comprehension
11) The human genome is minimally contained in which of the following?
A) every human cell
B) each human chromosome
C) the entire DNA of a single human
2
D) the entire human population
E) each human gene
Topic: Concept 13.1
Skill: Knowledge/Comprehension
12) Which of the following defines a genome?
A) representation of a complete set of a cell's polypeptides
B) the complete set of an organism's polypeptides
C) the complete set of a species' polypeptides
D) a karyotype
E) the complete set of an organism's genes
Topic: Concept 13.1
Skill: Knowledge/Comprehension
13) Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life
cycles have in common?
I. Alternation of generations
II. Meiosis
III. Fertilization
IV. Gametes
V. Spores
A) I, IV, and V
B) I, II, and IV
C) II, III, and IV
D) II, IV, and V
E) I, II, III, IV, and V
Topic: Concept 13.2
Skill: Knowledge/Comprehension
14) Which of these statements is false?
A) In humans, each of the 22 maternal autosomes has a homologous paternal chromosome.
B) In humans, the 23rd pair, the sex chromosomes, determines whether the person is female (XX) or male
(XY).
C) Single, haploid (n) sets of chromosomes in ovum and sperm unite during fertilization, forming a diploid (2n),
single-celled zygote.
D) At sexual maturity, ovaries and testes produce diploid gametes by meiosis.
E) Sexual life cycles differ with respect to the relative timing of meiosis and fertilization.
Topic: Concept 13.2
Skill: Knowledge/Comprehension
15) A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?
A) It must be human.
B) It must be a primate.
C) It must be an animal.
D) It must be sexually reproducing.
E) Its gametes must have 23 chromosomes.
Topic: Concept 13.2
3
Skill: Synthesis/Evaluation
16) After telophase I of meiosis, the chromosomal makeup of each daughter cell is
A) diploid, and the chromosomes are each composed of a single chromatid.
B) diploid, and the chromosomes are each composed of two chromatids.
C) haploid, and the chromosomes are each composed of a single chromatid.
D) haploid, and the chromosomes are each composed of two chromatids.
E) tetraploid, and the chromosomes are each composed of two chromatids.
Topic: Concept 13.3
Skill: Knowledge/Comprehension
17) Which of the following happens at the conclusion of meiosis I?
A) Homologous chromosomes are separated.
B) The chromosome number per cell is conserved.
C) Sister chromatids are separated.
D) Four daughter cells are formed.
E) The sperm cells elongate to form a head and a tail end.
Topic: Concept 13.3
Skill: Knowledge/Comprehension
18) Chromatids are separated from each other.
A) The statement is true for mitosis only.
B) The statement is true for meiosis I only.
C) The statement is true for meiosis II only.
D) The statement is true for mitosis and meiosis I.
E) The statement is true for mitosis and meiosis II.
Topic: Concept 13.3
Skill: Knowledge/Comprehension
19) Independent assortment of chromosomes occurs.
A) The statement is true for mitosis only.
B) The statement is true for meiosis I only.
C) The statement is true for meiosis II only.
D) The statement is true for mitosis and meiosis I.
E) The statement is true for mitosis and meiosis II.
Topic: Concept 13.3
Skill: Knowledge/Comprehension
20) Which of the following occurs in meiosis but not in mitosis?
A) chromosome replication
B) synapsis of chromosomes
C) production of daughter cells
D) alignment of chromosomes at the equator
E) condensation of chromatin
Topic: Concept 13.3
Skill: Knowledge/Comprehension
4