Question 1

RNA is believed to have been the original genetic system because it can
A) form a stable double helix with a complementary nucleic acid strand.
B) catalyze the polymerization of nucleotides into another RNA strand.
C) form ribosomes.
D) transfer amino acids to ribosomes.

Accepted Answer

RNA can catalyze its own replication, which is a key characteristic of genetic systems. This ability, known as RNA catalysis or ribozyme activity, is thought to have been critical in the evolution of early life forms. RNA's ability to form stable double helices and to form ribosomes are also important functions, but they do not directly relate to RNA's role as a genetic system. RNA cannot transfer amino acids to ribosomes – that is the job of transfer RNA (tRNA).

Question 2

The initial importance of membrane-enclosing, self-replicating RNA molecules and associated proteins was that they
A) maintained these molecules as a unit capable of reproduction and evolution.
B) provided sites for proteins to function.
C) transported materials in and out of the compartment.
D) kept other molecules out of the compartment.

Accepted Answer

The membrane-enclosing, self-replicating RNA molecules and associated proteins were important because they created a unit that could reproduce and evolve. This was the first step towards the development of living organisms as we know them today. The other choices (B, C, and D) are not as relevant to the initial importance of these molecules.

Question 3

Stanley Miller applied electric sparks to a reducing atmosphere of methane, ammonia, water, and hydrogen, and the resulting products showed that under these conditions,
A) amino acids can form.
B) nucleotides can form.
C) amino acids can polymerize into polypeptides.
D) nucleotides can polymerize into nucleic acids.

Accepted Answer

The Miller-Urey experiment demonstrated that amino acids, the building blocks of proteins, can form under simulated early Earth conditions with the application of electric sparks. The experiment did not demonstrate the formation of nucleotides or the polymerization of either amino acids or nucleotides.

Question 4

Which energy-producing process is thought to have come first during cellular evolution?
A) Photosynthesis
B) Glycolysis
C) Oxidative phosphorylation
D) Proteolysis

Accepted Answer

Glycolysis is thought to have come first during cellular evolution due to its simplicity and the fact that it occurs in all organisms, including anaerobic bacteria. Photosynthesis and oxidative phosphorylation are more complex and rely on specific organelles (chloroplasts and mitochondria, respectively), which were not present in the earliest cells. Proteolysis is not an energy-producing process.

Question 5

At the time life arose on Earth, Earth's atmosphere contained abundant amounts of all of the following except A) H₂. B) N₂. C) O₂. D) H₂S.

Accepted Answer

The early Earth's atmosphere was reducing and lacked free oxygen (O₂), which only became abundant after the Great Oxygenation Event caused by photosynthetic organisms.

Question 6

Organisms that evolved the ability to use H₂O as a donor of electrons and hydrogen for the photosynthetic conversion of CO₂ to organic compounds radically changed Earth by producing A) sugar. B) cellulose. C) H₂. D) O₂.

Accepted Answer

Organisms that evolved the ability to use H2S (hydrogen sulfide) as a donor of electrons and hydrogen for the photosynthetic conversion of CO2 (carbon dioxide) to organic compounds produced O2 (oxygen), which radically changed Earth's atmosphere.

Question 7

The feature that most clearly distinguishes eukaryotes from prokaryotes is the presence of _______ in eukaryotic cells.
A) ribosomes
B) oxidative phosphorylation
C) RNA molecules
D) a nucleus

Accepted Answer

The presence of a nucleus, which houses the genetic material, is the feature that most clearly distinguishes eukaryotic cells from prokaryotic cells. While ribosomes, oxidative phosphorylation, and RNA molecules are also present in eukaryotic cells (and prokaryotic cells), the presence of a nucleus is unique to eukaryotes.

Question 8

Cytoplasmic organelles are
A) absent in prokaryotic cells and present in eukaryotic cells.
B) present in both prokaryotic and eukaryotic cells.
C) present in prokaryotic cells and absent in eukaryotic cells.
D) absent in both prokaryotic and eukaryotic cells.

Accepted Answer

Cytoplasmic organelles, such as mitochondria, chloroplasts, and Golgi apparatus, are present only in eukaryotic cells and are absent in prokaryotic cells. Therefore, option A is correct.

Question 9

The eukaryotic nucleus contains _______ DNA molecule(s).
A) a single linear
B) a single circular
C) multiple linear
D) multiple circular

Accepted Answer

Eukaryotic nuclei contain multiple linear DNA molecules, organized into chromosomes.

Question 10

The bacterial genome is located in a portion of the cell called the
A) nucleus.
B) nucleolus.
C) mesosome.
D) nucleoid.

Accepted Answer

The bacterial genome is not located in a true nucleus like in eukaryotic cells, but instead is located within a region called the nucleoid. The nucleoid is a condensed region of the cell that contains the single, circular chromosome of the bacterium. Choices A, B, and C are incorrect because they do not refer to the correct location of the bacterial genome.

Question 11

Eukaryotic cell nuclei contain genes that are
A) primarily of bacterial origin.
B) primarily of archaebacterial origin.
C) partly archaebacterial and partly bacterial in origin.
D) all of eukaryotic origin.

Accepted Answer

Eukaryotic cell nuclei contain genes that are a mix of both archaebacterial and bacterial origins due to the endosymbiotic events and horizontal gene transfer that occurred during the evolution of eukaryotes.

Question 12

Organelles such as mitochondria and chloroplasts are thought to have originated in eukaryotic cells via a process called
A) phagocytosis.
B) endosymbiosis.
C) endocytosis.
D) exocytosis.

Accepted Answer

Mitochondria and chloroplasts are thought to have originated in eukaryotic cells through a process called endosymbiosis, in which a prokaryotic organism is engulfed by a eukaryotic cell and evolves over time to become a permanent resident within the host cell. This process eventually gave rise to modern-day mitochondria and chloroplasts, which share many characteristics with bacterial cells and have their own DNA and ribosomes.

Question 13

Mitochondria and chloroplasts resemble bacteria in that they
A) have their own DNA.
B) have their own ribosomes.
C) reproduce by simple division into two.
D) All of the above

Accepted Answer

Mitochondria and chloroplasts have their own DNA, which is circular and much like bacterial DNA. They also have their own ribosomes, which are similar in size and structure to bacterial ribosomes. Additionally, they reproduce by a simple division process, much like bacteria.

Question 14

Which of the following is a colonial organism closely related to the evolutionary precursors of present-day plants?
A) Paramecium
B) Dictyostelium discoideum
C) Volvox
D) Arabidopsis thaliana

Accepted Answer

Volvox is a colonial green alga that is closely related to the evolutionary precursors of present-day plants. It is believed that the evolution of multicellular plants may have started with the formation of colonial organisms similar to Volvox. The other options, Paramecium and Dictyostelium discoideum, are unicellular organisms and Arabidopsis thaliana is a present-day plant species.

Question 15

The human body is composed of more than _______ different types of cells.
A) 100
B) 200
C) 400
D) 2,000

Accepted Answer

The human body is composed of more than 200 different types of cells, each specialized for various functions.

Question 16

E. coli is a useful model system for molecular biology studies because
A) it has a small genome.
B) it reproduces rapidly.
C) mutants can easily be isolated from culture dishes.
D) All of the above

Accepted Answer

E. coli has a small genome, reproduces rapidly, and mutants can easily be isolated from culture dishes. All of these characteristics make it a useful model system for molecular biology studies.

Question 17

A yeast cell divides in culture about every
A) 20 minutes.
B) 40 minutes.
C) 2 hours.
D) 12 hours.

Accepted Answer

The answer of A yeast cell divides in culture about...

Question 18

How many genes does the haploid yeast nuclear genome contain?
A) 1,000
B) 6,000
C) 10,000
D) 20,000

Accepted Answer

The haploid yeast (Saccharomyces cerevisiae) nuclear genome contains approximately 6,000 genes.

Question 19

The adult nematode worm Caenorhabditis elegans consists of _______ somatic cells.
A) 95
B) 959
C) 1,500
D) 9,590

Accepted Answer

The adult nematode worm Caenorhabditis elegans consists of approximately 959 somatic cells. The exact number has been subject to some debate and may fluctuate slightly depending on the individual worm, but the consensus is around 959 cells.

Question 20

The simplicity and clarity of Caenorhabditis elegans allowed researchers to
A) trace the developmental lineages of all cells in the adult.
B) identify the genes involved in differentiation of each cell type.
C) observe the process of fertilization better than had been possible in the past.
D) follow the process by which cell aggregation forms a multicellular organism.

Accepted Answer

The simplicity and transparency of C. elegans have enabled researchers to map the entire cell lineage from the fertilized egg to the adult, tracing the developmental fate of each cell.

Quiz 1: An Overview of Cells and Cell Research

RNA is believed to have been the original genetic system because it can

The initial importance of membrane-enclosing, self-replicating RNA molecules and associated proteins was that they

Stanley Miller applied electric sparks to a reducing atmosphere of methane, ammonia, water, and hydrogen, and the resulting products showed that under these conditions,

Which energy-producing process is thought to have come first during cellular evolution?

At the time life arose on Earth, Earth's atmosphere contained abundant amounts of all of the following except

Organisms that evolved the ability to use H₂O as a donor of electrons and hydrogen for the photosynthetic conversion of CO₂ to organic compounds radically changed Earth by producing

The feature that most clearly distinguishes eukaryotes from prokaryotes is the presence of _______ in eukaryotic cells.

Cytoplasmic organelles are

The eukaryotic nucleus contains _______ DNA molecule(s) .

The bacterial genome is located in a portion of the cell called the

Eukaryotic cell nuclei contain genes that are

Organelles such as mitochondria and chloroplasts are thought to have originated in eukaryotic cells via a process called

Mitochondria and chloroplasts resemble bacteria in that they

Which of the following is a colonial organism closely related to the evolutionary precursors of present-day plants?

The human body is composed of more than _______ different types of cells.

E. coli is a useful model system for molecular biology studies because

A yeast cell divides in culture about every

How many genes does the haploid yeast nuclear genome contain?

The adult nematode worm Caenorhabditis elegans consists of _______ somatic cells.

The simplicity and clarity of Caenorhabditis elegans allowed researchers to