PCB 3023 Final Exam | Comprehensive
Questions and Answers plus Rationale | New
Update 2026-2027
THE NATURE OF LIFE AND CELLS
Question 1
Living systems are incredibly diverse in size, shape, environment, and behavior.
It is estimated that there are between 10 million and 100 million different
species. Despite this wide variety of organisms, it remains difficult to define
what it means to say something is alive. Which of the following can be described
as the smallest living unit?
A. DNA
B. Cell
C. Organelle
D. Protein
Correct Answer: B. Cell
Expert Rationale: The cell is the smallest unit of life that can carry out all the
functions necessary for life—metabolism, reproduction, response to stimuli,
homeostasis, and heredity. DNA (A) and proteins (D) are molecules that are not
alive on their own; they require cellular machinery to function. Organelles (C) are
subcellular structures that cannot survive or reproduce independently. The cell
theory, established in the mid-1800s, established that cells are the fundamental
unit of life.
Question 2
The flow of genetic information is controlled by a series of biochemical reactions
that result in the production of proteins, each with its own specific order of
amino acids. Choose the correct series of biochemical reactions from the options
presented here.
,A. Replication, transcription, translation
B. Replication, translation, transcription
C. Translation, transcription, replication
D. Translation, replication, transcription
Correct Answer: A. Replication, transcription, translation
Expert Rationale: The central dogma of molecular biology describes the flow of
genetic information as: DNA → RNA → Protein. Replication copies DNA to make
more DNA. Transcription synthesizes RNA from a DNA template. Translation
synthesizes proteins from the RNA template. This order is essential: genetic
information is first stored in DNA, then copied to RNA, and finally used to build
proteins. The correct sequence is replication, transcription, translation.
Question 3
Proteins are important architectural and catalytic components within the cell,
helping to determine its chemistry, its shape, and its ability to respond to
changes in the environment. Remarkably, all of the different proteins in a cell
are made from the same 20 __________. By linking them in different sequences,
the cell can make protein molecules with different conformations and surface
chemistries, and therefore different functions.
A. Nucleotides
B. Sugars
C. Amino acids
D. Fatty acids
Correct Answer: C. Amino acids
Expert Rationale: Proteins are polymers of amino acids. There are 20 standard
amino acids that are used to build proteins in all living organisms. The sequence of
these amino acids determines the protein's primary structure, which then folds
into a specific 3D conformation and determines its function. Nucleotides (A) build
nucleic acids; sugars (B) build carbohydrates; fatty acids (D) build lipids. Only
amino acids are the building blocks of proteins.
,Question 4
Which statement is NOT true about mutations?
A. A mutation is a change in the DNA that can generate offspring less fit for
survival than their parents.
B. A mutation can be a result of imperfect DNA duplication.
C. A mutation is a result of sexual reproduction.
D. A mutation is a change in the DNA that can generate offspring that are as fit for
survival as their parents are.
Correct Answer: C. A mutation is a result of sexual reproduction.
Expert Rationale: Mutations are changes in the DNA sequence that arise from
errors during DNA replication (imperfect duplication, B), exposure to mutagens, or
other random events. Sexual reproduction (C) does not cause mutations; it
shuffles existing genetic variation through recombination. While sexual
reproduction can bring together mutated alleles, it is not a source of mutation.
Mutations can reduce fitness (A), increase fitness, or have no effect (D). Therefore,
C is NOT true.
Question 5
Changes in DNA sequence from one generation to the next may result in
offspring that are altered in fitness compared with their parents. The process of
change and selection over the course of many generations is the basis of
__________.
A. Mutation
B. Evolution
C. Heredity
D. Reproduction
Correct Answer: B. Evolution
Expert Rationale: Evolution is the process by which populations of organisms
change over generations through mechanisms such as mutation, natural selection,
genetic drift, and gene flow. Mutation (A) is the source of new genetic variation,
, not the process of change over generations. Heredity (C) is the transmission of
traits from parents to offspring. Reproduction (D) is the process by which
organisms produce offspring. Evolution encompasses the cumulative changes in
populations over many generations.
Question 6
Select the option that best finishes the following statement: "Evolution is a
process __________."
A. That can be understood based on the principles of mutation and selection.
B. That results from repeated cycles of adaptation over billions of years.
C. By which all present-day cells arose from 4-5 different ancestral cells.
D. That requires hundreds of thousands of years.
Correct Answer: A. That can be understood based on the principles of mutation
and selection.
Expert Rationale: Evolution is understood through the mechanisms of mutation
(generating variation) and natural selection (acting on that variation) along with
genetic drift and gene flow. While evolution has occurred over billions of years (B),
the statement "based on mutation and selection" best captures the mechanistic
basis. Present-day cells arose from a single common ancestor (C is false—the
universal common ancestor hypothesis suggests one ancestral cell). Evolution can
occur on various timescales, not requiring hundreds of thousands of years (D is
false—bacteria can evolve in days).
Question 7
Select the option that correctly finishes the following statement: "A cell's
genome _________________."
A. Is defined as all the genes being used to make protein.
B. Contains all of a cell's DNA.
C. Constantly changes, depending upon the cell's environment.
D. Is altered during embryonic development.
Questions and Answers plus Rationale | New
Update 2026-2027
THE NATURE OF LIFE AND CELLS
Question 1
Living systems are incredibly diverse in size, shape, environment, and behavior.
It is estimated that there are between 10 million and 100 million different
species. Despite this wide variety of organisms, it remains difficult to define
what it means to say something is alive. Which of the following can be described
as the smallest living unit?
A. DNA
B. Cell
C. Organelle
D. Protein
Correct Answer: B. Cell
Expert Rationale: The cell is the smallest unit of life that can carry out all the
functions necessary for life—metabolism, reproduction, response to stimuli,
homeostasis, and heredity. DNA (A) and proteins (D) are molecules that are not
alive on their own; they require cellular machinery to function. Organelles (C) are
subcellular structures that cannot survive or reproduce independently. The cell
theory, established in the mid-1800s, established that cells are the fundamental
unit of life.
Question 2
The flow of genetic information is controlled by a series of biochemical reactions
that result in the production of proteins, each with its own specific order of
amino acids. Choose the correct series of biochemical reactions from the options
presented here.
,A. Replication, transcription, translation
B. Replication, translation, transcription
C. Translation, transcription, replication
D. Translation, replication, transcription
Correct Answer: A. Replication, transcription, translation
Expert Rationale: The central dogma of molecular biology describes the flow of
genetic information as: DNA → RNA → Protein. Replication copies DNA to make
more DNA. Transcription synthesizes RNA from a DNA template. Translation
synthesizes proteins from the RNA template. This order is essential: genetic
information is first stored in DNA, then copied to RNA, and finally used to build
proteins. The correct sequence is replication, transcription, translation.
Question 3
Proteins are important architectural and catalytic components within the cell,
helping to determine its chemistry, its shape, and its ability to respond to
changes in the environment. Remarkably, all of the different proteins in a cell
are made from the same 20 __________. By linking them in different sequences,
the cell can make protein molecules with different conformations and surface
chemistries, and therefore different functions.
A. Nucleotides
B. Sugars
C. Amino acids
D. Fatty acids
Correct Answer: C. Amino acids
Expert Rationale: Proteins are polymers of amino acids. There are 20 standard
amino acids that are used to build proteins in all living organisms. The sequence of
these amino acids determines the protein's primary structure, which then folds
into a specific 3D conformation and determines its function. Nucleotides (A) build
nucleic acids; sugars (B) build carbohydrates; fatty acids (D) build lipids. Only
amino acids are the building blocks of proteins.
,Question 4
Which statement is NOT true about mutations?
A. A mutation is a change in the DNA that can generate offspring less fit for
survival than their parents.
B. A mutation can be a result of imperfect DNA duplication.
C. A mutation is a result of sexual reproduction.
D. A mutation is a change in the DNA that can generate offspring that are as fit for
survival as their parents are.
Correct Answer: C. A mutation is a result of sexual reproduction.
Expert Rationale: Mutations are changes in the DNA sequence that arise from
errors during DNA replication (imperfect duplication, B), exposure to mutagens, or
other random events. Sexual reproduction (C) does not cause mutations; it
shuffles existing genetic variation through recombination. While sexual
reproduction can bring together mutated alleles, it is not a source of mutation.
Mutations can reduce fitness (A), increase fitness, or have no effect (D). Therefore,
C is NOT true.
Question 5
Changes in DNA sequence from one generation to the next may result in
offspring that are altered in fitness compared with their parents. The process of
change and selection over the course of many generations is the basis of
__________.
A. Mutation
B. Evolution
C. Heredity
D. Reproduction
Correct Answer: B. Evolution
Expert Rationale: Evolution is the process by which populations of organisms
change over generations through mechanisms such as mutation, natural selection,
genetic drift, and gene flow. Mutation (A) is the source of new genetic variation,
, not the process of change over generations. Heredity (C) is the transmission of
traits from parents to offspring. Reproduction (D) is the process by which
organisms produce offspring. Evolution encompasses the cumulative changes in
populations over many generations.
Question 6
Select the option that best finishes the following statement: "Evolution is a
process __________."
A. That can be understood based on the principles of mutation and selection.
B. That results from repeated cycles of adaptation over billions of years.
C. By which all present-day cells arose from 4-5 different ancestral cells.
D. That requires hundreds of thousands of years.
Correct Answer: A. That can be understood based on the principles of mutation
and selection.
Expert Rationale: Evolution is understood through the mechanisms of mutation
(generating variation) and natural selection (acting on that variation) along with
genetic drift and gene flow. While evolution has occurred over billions of years (B),
the statement "based on mutation and selection" best captures the mechanistic
basis. Present-day cells arose from a single common ancestor (C is false—the
universal common ancestor hypothesis suggests one ancestral cell). Evolution can
occur on various timescales, not requiring hundreds of thousands of years (D is
false—bacteria can evolve in days).
Question 7
Select the option that correctly finishes the following statement: "A cell's
genome _________________."
A. Is defined as all the genes being used to make protein.
B. Contains all of a cell's DNA.
C. Constantly changes, depending upon the cell's environment.
D. Is altered during embryonic development.
