Exam 2-Mastering Biology Questions Flashcards
1
Q
RNA molecules can both carry genetic information and be catalytic. This supports the proposal that:
A. protobionts had an RNA membrane
B. free nucleotides would not have been necessary ingredients in the synthesis of new RNA molecules
C. RNA is a polymer of amino acids
D. RNA could make energy
E. RNA was the first hereditary information
A
E. RNA was the first hereditary information (Because RNA can catalyze synthesis of new RNA)
2
Q
Approximately how far back in time does the fossil record extend?
A. 3,500,000 years
B. 3,500,000,000 years
C. 5,000,000,000 years
D. 6,000,000 years
E. 6,000 years
A
B. 3,500,000,000
3
Q
An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to:
A. cause iron in ocean water and terrestrial rocks to rust (oxidize)
B. make it easier to maintain reduced molecules
C. change the atmosphere from oxidizing to reducing
D. make life on land difficult for aerobic organisms
E. prevent the formation of an ozone layer
A
A. cause iron in ocean water and terrestrial rocks to rust (oxidize)
4
Q
Which free-living cells were the earliest contributors to the formation of Earth’s oxidizing atmosphere?
A. seaweeds
B. mitochondria
C. cyanobacteria
D. endosymbionts
E. chloroplasts
A
C. cyanobacteria
5
Q
Which of the following statements provides the strongest evidence that prokaryotes evolved before eukaryotes?
A. meteorites that have struck Earth
B. the primitive structure of plants
C. Liposomes closely resemble prokaryotic cells
D. abiotic laboratory experiments that produced liposomes
E. the oldest fossilized cells resemble prokaryotes
A
E. the oldest fossilized cells resemble prokaryotes
6
Q
What is thought to be the correct sequence of these events, from earliest to most recent, in the evolution of life on Earth? 1. origin of mitochondria 2.origin of multicellular eukaryotes 3. origin of chloroplasts 4. origin of cyanobacteria 5. origin of fungal-plant symbioses
A. 4, 3, 2, 1, 5
B. 4, 3, 1, 5, 2
C. 4, 1, 2, 3, 5
D. 4, 1, 3, 2, 5
E. 3, 4, 1, 2, 5
A
D. 4, 1, 3, 2, 5 (cyanobacteria > mitochondria > chloroplasts > multicellular eukaryotes > fungal-plant symbioses)
7
Q
Penicillin is an antibiotic that inhibits enzymes from catalyzing the synthesis of peptidoglycan, so which prokaryotes should be most vulnerable to inhibition by penicillin?
A. gram-positive bacteria
B. archaea
C. endospore-bearing bacteria
D. gram-negative bacteria
E. mycoplasmas
A
A. gram-positive bacteria (because what makes cells gram-positive is their lack of a lipopolysaccharide membrane above the peptidoglycan membrane. This would make it so the antibiotic could break down the cell membrane)
8
Q
Which two structures play direct roles in permitting bacteria to adhere to each other, or to other surfaces?
A. capsules and fimbriae
B. capsules and endospores
C. fimbriae and flagella
D. fimbriae and plasmids
E. endospores and fimbriae
A
A. capsules and fimbriae
9
Q
The typical prokaryotic flagellum features:
A. an internal 9+2 pattern of microtubules
B. a complex “motor” embedded in the cell wall and plasma membrane
C. an external covering provided by the plasma membrane
D. a basal body that is similar in structure to the cell’s centrioles
A
B. a complex “motor” embedded in the cell wall and plasma membrane
10
Q
An organism that obtains its energy from chemicals:
A. autotroph only
B. heterotroph only
C. chemotroph only
D. phototroph only
E. autotroph and chemotroph
A
C. chemotroph only
11
Q
A prokaryote that obtains both energy and carbon as it decomposes dead organisms:
A. chemotroph only
B. autotroph only
C. autotroph, phototroph, and chemotroph
D. autotroph and phototroph
E. heterotroph and chemotroph
A
E. heterotroph and chemotroph
12
Q
Protists are alike in that all are:
A. symbionts
B. monophyletic
C. autotrophic
D. eukaryotic
E. unicellular
A
D. eukaryotic
13
Q
According to the endosymbiotic theory of the origin of eukaryotic cells, how did mitochondria originate?
A. from the nuclear envelope folding outward and forming mitochondrial membranes
B. from infoldings of the plasma membrane, coupled with mutations of genes for proteins in energy-transfer reactions
C. by secondary endosymbiosis
D. when a protoeukaryote engaged in a symbiotic relationship with a protobiont
E. from engulfed, originally free-living prokaryotes
A
E. from engulfed, originally free-living prokaryotes
14
Q
The chloroplasts of land plants are thought to have been derived according to which evolutionary sequence?
A. cyanobacteria > green algae > land plants
B. red algae > cyanobacteria > land plants
C. red algae > brown algae > green algae > land plants
D. cyanobacteria > red algae > green algae > land plants
E. cyanobacteria > green algae > fungi > land plants
A
A. Cyanobacteria > green algae > land plants
15
Q
Which taxon of eukaryotic organisms is thought to be directly ancestral to the plant kingdom?
A. radiolarians
B. apicomplexans
C. golden algae
D. green algae
E. foraminiferans
A
D. green algae
16
Q
Which is the correct sequence of these events in the origin of life? 1. formation of protobionts 2. synthesis of organic monomers 3. synthesis of organic polymers 4. formation of DNA-based genetic systems
A. 3, 2, 1, 4
B. 2, 3, 1, 4
C. 1, 2, 3, 4
D. 4, 3, 1, 2
E. 1, 3, 2, 4
A
B. 2, 3, 1, 4 (organic monomers > organic polymers > protobionts > DNA-based genetic systems)
17
Q
Which is a defining characteristic that all protobionts had in common?
A. a surrounding membrane or membrane-like structure
B. a nucleus
C. the ability to replicate RNA
D. RNA genes
E. the ability to synthesize enzymes
A
A. a surrounding membrane or membrane-like structure
18
Q
Which of these is a receptor molecule?
A
B
19
Q
A signal transduction pathway is initiated when a _____ binds to a receptor.
G protein
cyclic AMP
signal molecule
calmodulin tyrosine kinase
A
Signal Molecule
20
Q
Which of these is a signal molecule?
A
A
21
Q
A signal molecule is also known as a(n) _____.
ligand key protein initiator receptor
A
Ligand
22
Q
Which of these is the second of the three stages of cell signaling?
gene activation reception binding of a neurotransmitter to a plasma membrane receptor transduction cell response
A
Transduction
23
Q
Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?
synaptic signaling hormonal signaling autocrine signaling paracrine signaling
A
Paracrive Signaling
24
Q
Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must _____.
experience an imbalance that disrupts its normal function modify its plasma membrane to alter the hormone entering the cytoplasm be from the same cell type as the organ that produced the hormone have receptors that recognize and bind the hormone molecule
A
Have receptors that recognize and bind the hormone molecule
25
When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?
transducer signal molecule response molecule relay molecule
Signal Molecule
26
In the figure, the dots in the space between the two structures represent which of the following?
neurotransmitters signal transducers hormones receptor molecules
Neurotransmitters
27
A G-protein receptor with GTP bound to it \_\_\_\_\_.
will use cGMP as a second messenger is in its active state directly affects gene expression signals a protein to maintain its shape and conformation
Is in its active state
28
One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?
G protein-coupled receptors receptor tyrosine kinases ligand-gated ion channels steroid receptors
Receptor Tyrosine Kinases
29
Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because \_\_\_\_\_.
only target cells retain the appropriate DNA segments only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor only target cells possess the cytosolic enzymes that transduce the testosterone intracellular receptors are present only in target cells
Intracellular receptors are present only in target cells
30
Which of the following is characteristic of a steroid hormone action?
cell-surface receptor binding second messenger activation internal receptor binding protein phosphorylation
Internal receptor binding
31
Which of these acts as a second messenger?
E B D A C
D acts as a second messenger
32
Which of these is responsible for initiating a signal transduction pathway?
A B C D E
A is responsible for initiating a signal transduction pathway
\* This is a signal molecule. The attachment of a signal molecule to a plasma membrane receptor initiates a signal transduction pathway.
33
What role does a transcription factor play in a signal transduction pathway?
By binding to a plasma membrane receptor it initiates a cascade. It relays a signal from the cytoplasm to the plasma membrane. It activates relay proteins. By binding to DNA it triggers the transcription of a specific gene. It is a plasma membrane protein that binds signal molecules.
By binding to DNA it triggers the transcription of a specific gene.
34
Which of the following, when activated by a signal transduction pathway, moved from the cytoplasm to the nucleus of a cell?
relay protein DNA plasma membrane receptor protein signal molecule transcription factor
Transcription Factor
35
Which of these is a membrane receptor?
A B C D E
B is a membrane receptor
36
A signal transduction pathway is initiated when a _____ binds to a receptor.
G protein tyrosine kinase calmodulin signal molecule cyclic AMP
Signal Molecule
37
Which of these acts as a second messenger?
G-protein-linked receptor cyclic AMP protein kinase adenylyl kinase G protein
Cyclic AMP
38
Calcium ions that act as second messengers are stored in \_\_\_\_\_.
mitochondria peroxisomes endoplasmic reticula lysosomes chloroplasts
Endoplasmic Reticula
39
\_\_\_\_\_ catalyzes the production of \_\_\_\_\_, which then opens an ion channel that releases _____ into the cell's cytoplasm.
Phospholipase C ... IP3 .... Ca2+ Adenylyl cyclase ... IP3 .... Ca2+ Phospholipase C ... cyclic AMP ... Ca2+ Protein kinase ... PIP2 ... Na+ Adenylyl cyclase ... cyclic AMP ... Ca2+
Phospholipase C ... IP3 .... Ca2+
\* Phospholipase C cleaves IP3 from a membrane protein, and IP3 then binds to a calcium channel on the ER.
40
A protein kinase activating many other protein kinases is an example of \_\_\_\_\_.
a cellular response amplification deactivation sensitization mutualism
Amplification
41
Which of the following statements is true of signal molecules?
In most cases, signal molecules interact with the cell at the plasma membrane, enter the cell, and eventually enter the nucleus. When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules. Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors. In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium.
Protein kinase A activation is one possible result of signal molecules bining to G-protein-coupled receptors.
42
Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting \_\_\_\_\_.
the hydrolysis of GTP to GDP the removal of GMP from the cell the dephosphorylation of cGMP the hydrolysis of cGMP to GMP
The hydrolysis of cGMP to GMP
43
Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. The second messenger in this pathway is \_\_\_\_\_.
G protein cAMP adenylyl cyclase G protein-coupled receptor
cAMP
44
Scaffolding proteins are \_\_\_\_\_.
large molecules to which several relay proteins attach to facilitate cascade effects proteins that can reach into the nucleus of a cell to affect transcription microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing
large molecules to which several relay proteins attach to facilitate cascade effects
45
GTPase activity is important in the regulation of signal transduction because it \_\_\_\_\_.
decreases the amount of G protein in the membrane increases the available concentration of phosphate converts cGMP to GTP hydrolyzes GTP to GDP, thus shutting down the pathway
Hydrolyzes GTP to GDP, thus shutting down the pathway
46
Which of the following describes the events of apoptosis?
The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized. The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells. The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled. The cell's nucleus and organelles are lysed, then the cell enlarges and bursts.
The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells.
47
Cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death." This controlled cell suicide is called apoptosis. Select the appropriate description of this event on a cell's life cycle.
During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell. Apoptosis is regulated by cell surface receptors that signal when a cell has reached its density-dependent limits. Each cell organelle has protein signals that initiate the breakdown of the organelle's components which leads to cell death. During apoptosis, dying cells leak out their contents including digestive enzymes that also destroy healthy cells.
During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell.
48
Apoptosis involves all but which of the following?
fragmentation of the DNA digestion of cellular contents by scavenger cells lysis of the cell activation of cellular enzymes cell-signaling pathways
Lysis of the cell
49
Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor on target cells is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine.
Which statements are true about the binding of histamine to the histamine H1 receptor? Select all that apply.
Histamine diffuses across the plasma membrane to bind to the H1 receptor. Histamine binds extracellularly to the H1 receptor. When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein. Histamine binds intracellularly to the inactive G protein, activating the G protein. Once the G protein is active, it binds to the enzyme phospholipase C, activating it. Histamine is likely hydrophilic.
* Histamine binds extracellularly to the H1 receptor.
* When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein
* Once the G protein is active, it binds to the enzyme phospholipase C, activating it.
* Histamine is likely hydrophilic.
\* When histamine encounters a target cell, it binds extracellularly to the H1 receptor, causing a change in the shape of the receptor. This change in shape allows the G protein to bind to the H1 receptor, causing a GTP molecule to displace a GDP molecule and activating the G protein. The active G protein dissociates from the H1 receptor and binds to the enzyme phospholipase C, activating it. The active phospholipase C triggers a cellular response. The G protein then functions as a GTPase and hydrolyzes the GTP to GDP. The G protein dissociates from the enzyme and is inactive again and ready for reuse.
50
Cortisol is a steroid hormone that can pass through the plasma membrane. Complete the flowchart describing the interaction of cortisol with intracellular receptors.
1. \>\>\> 2. \>\>\> 3. \>\>\> 4. \>\>\> 5.
A. Cortisol passes through the plasma membrane into the cytoplasm.
B. Cortisol-receptor complex forms in the cytoplasm.
C. Cortisol binds to a receptor on the outside of the cell.
D. The transcribed mRNA is translated into a specific protein
E. Cortisol-receptor complex enters the nucleus where it binds to genes.
F. Cortisol-receptor complex forms in the nucleus.
G. Cortisol-receptor complex acts as a transcription factor.
1. A \>\>\> 2. B \>\>\> 3. E \>\>\> 4. G \>\>\> 5. D
\* Cortisol is a small, hydrophobic steroid hormone that can pass through the plasma membrane of cells. In target cells, cortisol binds to the intracellular receptor protein in the cytoplasm, forming a hormone-receptor complex. The hormone-receptor complex then moves into the nucleus and acts as a transcription factor, binding to specific genes and activating their transcription into mRNA. The mRNA that is produced is eventually translated into specific proteins.
Proteins produced in response to the cortisol signal function in the stress response. For example, some of these proteins aid in elevating glucose levels in the blood, helping an animal to meet the demands of starvation or intense physical activity.
51
Unlike steroid hormones, signaling molecules that are large and/or hydrophilic cannot pass through the cell’s plasma membrane and therefore must bind extracellularly to receptor molecules in the plasma membrane. Two types of signal receptors embedded in the cell's plasma membrane are G protein-coupled receptors and receptor tyrosine kinases. Classify each phrase by whether it applies to G protein-coupled receptors only, receptor tyrosine kinases only, both receptors, or neither receptor.
{G protein-coupled receptors}
{receptor tyrosine kinases}
{both types of receptors}
{neither receptor}
A. binding of the signaling molecule forms a dimer
B. binding of the signaling molecule allows ions to flow through a channel in the receptor
C. binding site for signaling molecule is located on the extracellular side of the cell
D. interact directly with G proteins
E. catalyzes the transfer of a phosphate group to the receptor
F. receptor is located in the plasma membrane
{G protein-coupled receptors} D
{receptor tyrosine kinases} A, E
{both types of receptors} C, F
{neither receptor} B
\*Both G protein-coupled receptors and receptor tyrosine kinases are transmembrane receptors that have a binding domain located on the extracellular side of the plasma membrane. The binding of a signaling molecule to these receptors is the first step in a signaling pathway. However, what happens after a signaling molecule binds is different for each receptor.
An activated G protein-coupled receptor activates a G protein inside the cell, which involves the release of GDP and the binding of GTP. The activated G protein then activates an associated enzyme, leading to a cellular response.
Receptor tyrosine kinases form dimers after binding signaling molecules. The tyrosines are then phosphorylated, fully activating the receptor. Each phosphorylated tyrosine can bind a relay protein, each of which can trigger a transduction pathway. In this way, a single signaling-molecule binding event can trigger multiple signal transduction pathways and thus multiple cellular responses.
52
What are the functions of signal transduction pathways?
Select all that apply.
Signal transduction pathways allow different types of cells to respond differently to the same signal molecule. Signal transduction pathways convert a signal on a cell’s surface to a specific cellular response. Signal transduction pathways amplify the effect of a signal molecule.
All of the above
53
Which statement correctly distinguishes the roles of protein kinases and protein phosphatases in signal transduction pathways?
Protein kinases are involved in signal transduction in unicellular eukaryotes such as yeast. Protein phosphatases are involved in signal transduction in multicellular eukaryotes. Protein kinases are more critical than protein phosphatases to signal transduction enzymes. Protein kinases activate enzymes by phosphorylating or adding phosphate groups to them. Protein phosphatases dephosphorylate or remove phosphate groups from enzymes, including protein kinases.
Protein kinases activate enzymes by phosphorylating or adding phosphate groups to them. Protein phosphorylate or remove phosphate groups from enzymes, including protein kinases.
54
All protists are \_\_\_\_\_.
mixotrophic eukaryotic unicellular symbionts
eukaryotic
55
Why has the kingdom Protista been abandoned?
Some protists are multicellular. The kingdom Protista is polyphyletic. Some protists are more closely related to plants, animals, or fungi than they are to other protists. Some protists are as small as prokaryotes. The second and third answers are correct.
The second and third answers are correct
56
Nucleoli are present during \_\_\_\_\_\_\_.
A. metaphase
B. prophase
C. prometaphase
D. anaphase
E. interphase
E. interphase
57
Cytokinesis often, but not always accompanies \_\_\_\_\_.
A. interphase
B. metaphase
C. anaphase
D. prometaphase
E. telophase
E. telophase
58
Chromosomes become visible during\_\_\_\_\_.
A. prometaphase
B. metaphase
C. interphase
D. prophase
E. anaphase
D. prophase
59
Centromeres divide and sister chromatids become full-fledged chromosomes during \_\_\_\_\_.
A. telophase
B. interphase
C. metaphase
D. anaphase
E. prometaphase
D. anaphase
60
Spindle fibers attach to kinetochores during \_\_\_\_\_.
A. anaphase
B. interphase
C. metaphase
D. telophase
E. prometaphase
E. prometaphase
61
During prophase a homologous pair of chromosomes consists of \_\_\_\_.
A. two chromosomes and four chromatids
B. one chromosome and two chromatids
C. one chromosome and four chromatids
D. four chromosomes and two chromatids
E. two chromosomes and two chromatids
A. two chromosomes and four chromatids
62
Which of these phases encompasses all of the stages of mitosis?
## Footnote
E
63
During _____ both the contents of the nucleus and the cytoplasm are divided.
mitosis the mitotic phase G1 S G2
The Mitotic phase
64
During _____ the cell grows and replicates both its organelles and its chromosomes.
## Footnote
cytokinesis G1 mitosis interphase S
Interphase
65
In eukaryotic cells, chromosomes are composed of \_\_\_\_\_.
DNA and proteins DNA and RNA DNA and phospholipids DNA only
DNA and proteins
66
What is the final result of mitosis in a human?
genetically identical 2n gamete cells genetically identical 2n somatic cells genetically identical 1n somatic cells genetically different 2n somatic cells
Genetically identical 2n somatic cells
67
Which of the following correctly matches a phase of the cell cycle with its description?
M: duplication of DNA G1: follows cell division G2: cell division S: immediately precedes cell division All of the above are correctly matched.
G1: follows cell division
68
Some cells have several nuclei per cell. How could such multinucleated cells be explained?
The cell underwent repeated mitosis, but cytokinesis did not occur. The cell underwent repeated cytokinesis but no mitosis. The cell underwent repeated mitosis with simultaneous cytokinesis. The cell had multiple S phases before it entered mitosis.
The cell underwent repeated mitosis, but cytokinesis did not occur.
69
In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit \_\_\_\_\_.
the splitting of the centrosomes cytokinesis the attachment of microtubules to kinetochores the disassembly of the nucleolus
the attachment of microtubules to kinetochores
70
Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely \_\_\_\_\_.
an animal cell in the process of cytokinesis a plant cell in metaphase a plant cell in the process of cytokinesis an animal cell in the S phase of the cell cycle
a plant cell in the process of cytokinesis
71
Which of the following is a function of the S phase in the cell cycle?
The separation of sister chromatids The synthesis of sister chromatids The synchronization of organelle division The sorting of chromosomes
The synthesis of sister chromatids
72
The copying of chromosomes occurs during which of the following phases of the cell cycle?
G1 phase G2 phase S phase M phase
S phase
73
For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos?
The cells get smaller with each generation. The cells do not divide by mitosis. Frog embryos do not have DNA. The number of chromosomes decreases with each generation.
The cells get smaller with each generation.
74
True or false? The M phase is characterized by the replication and division of a cell's chromosomes.
false
75
If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?
68 136 17 34
34
76
Which of the following events would cause the cell cycle to arrest?
Complete chromosome replication Synthesis of cyclins by growth factors and activation of a cyclin-Cdk complex Poor nutrient conditions Chromosomes lined up along the metaphase plate
Poor nutrient conditions
77
Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?
cyclin Cdk MPF PDGF
MPF
78
Cyclin-dependent kinase (Cdk) is \_\_\_\_\_.
an enzyme that attaches phosphate groups to other proteins inactive, or "turned off," in the presence of cyclin the enzyme that catalyzes the attachment of chromosomes to microtubules present only during the S phase of the cell cycle
an enzyme that attaches phosphate groups to other proteins
79
Neurons and some other specialized cells divide infrequently because they \_\_\_\_\_.
no longer have active nuclei show a drop in MPF concentration have entered into G0 can no longer bind Cdk to cyclin
have entered into G0
80
In the cells of some organisms, mitosis occurs without cytoki-nesis. This will result in
cells lacking nuclei. cells that are unusually small. cells with more than one nucleus. cell cycles lacking an S phase. destruction of chromosomes.
cells with more than one nucleus.
81
Which statement provides the best description of the interphase portion of the cell cycle?
Interphase is a resting stage prior to cell division. During interphase, a cell is metabolically active. Interphase is a brief period between mitosis and chromosome duplication.
During interphase, a cell is metabolically active.
82
Which of the following does *not* occur during mitosis?
spindle formation separation of the spindle poles condensation of the chromosomes replication of the DNA separation of sister chromatids
replication of the DNA
83
What number and types of chromosomes are found in a human somatic cell?
44 autosomes and 2 sex chromosomes 22 autosomes and 1 sex chromosome *n* chromosomes 21 autosomes and 2 sex chromosomes 45 autosomes and 1 sex chromosome
44 autosomes and 2 sex chromosomes
84
How are sister chromatids and homologous chromosomes different from each other?
They are not different. Homologous chromosomes and sister chromatids are both identical copies of each other. Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. Homologous chromosomes are identical copies of each other. One sister chromatid comes from the father, and one comes from the mother. Sister chromatids are only formed during mitosis. Homologous chromosomes are formed during meiosis. Homologous chromosomes are closely associated with each other in both mitosis and meiosis. Sister chromatids are only associated with each other during mitosis.
Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.
85
Which of the following is a true statement about sexual vs. asexual reproduction?
In asexual reproduction, offspring are produced by fertilization without meiosis. Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi. Asexual reproduction produces only haploid offspring. In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.
In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.
86
Which of the following is true of a species that has a chromosome number of 2*n* = 16?
A gamete from this species has four chromosomes. The species has 16 sets of chromosomes per cell. Each diploid cell has eight homologous pairs. The species is diploid with 32 chromosomes per cell.
Each diploid cell has eight homologous pairs.
87
Homologous chromosomes \_\_\_\_\_.
carry information for the same traits are identical align on the metaphase plate in meiosis II carry the same alleles
carry information for the same traits
88
Meiosis I produces _____ cells, each of which is \_\_\_\_\_.
four ... diploid two... identical to the other two ... haploid two... diploid four ... haploid
two ... haploid
89
Meiosis II typically produces _____ cells, each of which is \_\_\_\_\_.
two ... haploid two... diploid four ... identical to the other four ... haploid four ... diploid
four ... haploid
90
During _____ sister chromatids separate.
prophase I interphase prophase II anaphase II metaphase I
anaphase II
91
At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
metaphase II telophase telophase I telophase II interphase
telophase I
92
Synapsis occurs during \_\_\_\_\_.
telophase I and cytogenesis prophase II anaphase II prophase I metaphase II
prophase I
93
Homologous chromosomes migrate to opposite poles during \_\_\_\_\_.
metaphase I prophase II metaphase II anaphase I telophase II and cytokinesis
anaphase I
94
During _____ chromosomes align single file along the equator of a haploid cell.
prophase I anaphase I telophase I and cytokinesis metaphase II metaphase I
metaphase II
95
At the end of _____ and cytokinesis there are four haploid cells.
prophase II prophase I telophase II anaphase I interphase
telophase II
96
During _____ a spindle forms in a haploid cell.
telophase I and cytokinesis prophase I metaphase II anaphase II prophase II
prophase II
97
Human gametes are produced by \_\_\_\_\_.
fertilization asexual reproduction the cell cycle meiosis mitosis
meiosis
98
Normal human gametes carry _____ chromosomes.
23 pairs of 23 5 46 pairs of 46
23
99
Which of these cells is (are) haploid?
B and C C and D D A and D B
C and D
100
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
32 64 16 8 30
16
101
Which of the following happens at the conclusion of meiosis I?
Homologous chromosomes of a pair are separated from each other. Sister chromatids are separated. The chromosome number per cell remains the same. Four daughter cells are formed.
Homologous chromosomes of a pair are separated from each other.
102
Which of the following occurs in meiosis but not in mitosis?
alignment of chromosomes at the equator synapsis of chromosomes chromosome replication condensation of chromosomes
synapsis of chromosomes
103
Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?
## Footnote
two a diploid number four eight
two
104
Which of the following can occur by the process of meiosis but not mitosis?
Haploid cells fuse to form diploid cells. A diploid cell combines with a haploid cell. Haploid cells multiply into more haploid cells. Diploid cells form haploid cells.
Diploid cells form haploid cells.
105
In meiosis, homologous chromosomes are separated during \_\_\_\_\_.
anaphase I anaphase II prophase I mitosis
anaphase I
106
Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?
9 38 10 19
38
107
Meiosis II is similar to mitosis in that
sister chromatids separate during anaphase. the daughter cells are diploid. the chromosome number is reduced. DNA replicates before the division. homologous chromosomes synapse.
sister chromatids separate during anaphase.
108
A human cell containing 22 autosomes and a Y chromosome is
a sperm. a zygote. a somatic cell of a male. a somatic cell of a female. an egg.
a sperm.
109
Look at the cell in the figure. Based on this figure, which of the following statements is true?
It is impossible to tell whether the cell is haploid or diploid. This cell is diploid. This cell is haploid.
This cell is diploid.
110
What is the difference between heterozygous and homozygous individuals?
The homozygote will express the dominant trait and the heterozygote will express the recessive trait. Homozygotes have one chromosome while heterozygotes have two similar chromosomes. All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ. Heterozygotes carry two copies of a gene while homozygotes only carry one.
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
111
When constructing a Punnett square, the symbols on the outside of the boxes represent \_\_\_\_\_\_\_, while those inside the boxes represent \_\_\_\_\_\_\_.
parents, gametes progeny, gametes gametes, parents gametes, progeny
gametes, progeny
112
True or false? The same phenotype can be produced by more than one genotype.
True False
True
113
True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
True False
False
114
If an organism with the genotype *AaBb* produces gametes, what proportion of the gametes would be *Bb*?
3/4 None 1/4 1/2
None
115
Two mice are heterozygous for albinism *(Aa)* . The dominant allele *(A)* codes for normal pigmentation, and the recessive allele *(a)* codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
25 100 50 75
25
116
A tall, purple-flowered pea plant *(TtPp)* is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?
*TtPp**TTPP**ttpp**TTpp*
*ttpp*
117
What process is responsible for the independent assortment of alleles?
DNA replication. Mitosis Cytokinesis. Meiosis.
Meiosis
118
How do cells acquire homologous chromosome pairs that carry the alleles that are independently assorted?
Meiosis Fusion of gametes Mitosis DNA replication
Fusion of gametes
119
Which of the following statements most accurately describes the process of independent assortment?
Alleles of different genes segregate from one another in a random manner. Genes located on the same chromosome assort as an independent unit. Dominant alleles segregate with recessive alleles. Alleles found on separate chromosomes segregate based upon their origin.
Alleles of different genes segregate from one another in a random manner.
120
True or false? The principle of independent assortment is best illustrated by events that take place during metaphase II, during which sister chromatids segregate independently of each other.
False
121
How many genetically unique types of gametes could be produced by an individual with the genotype *RrYY*?
Three One Eight Two
Two
122
Which of the following parental genotypes would yield a 1:1:1:1 phenotypic ratio in the offspring?
*aaBb, aabb**aaBb, AaBb**AaBb, AaBb**AaBb, aabb*
*AaBb, aabb*
123
What is an allele?
an alternative version of a gene a variety of pea plant used by Mendel the recessive form of a gene the dominant form of a gene a type of chromosome
an alternative version of a gene
124
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
Recessive genes occur more frequently in the F1 generation than do dominant ones. Genes are composed of DNA. Traits are inherited in discrete units and are not the results of "blending." There is considerable genetic variation in garden peas.
Traits are inherited in discrete units and are not the results of "blending."
125
Which of the following statements about independent assortment and segregation is correct?
The law of segregation is accounted for by anaphase of mitosis. The law of independent assortment requires describing two or more genes relative to one another. The law of segregation requires describing two or more genes relative to one another. The law of independent assortment is accounted for by observations of prophase I.
The law of independent assortment requires describing two or more genes relative to one another.
126
Mendel accounted for the observation that traits that had disappeared in the F1 generation reappeared in the F2generation by proposing that \_\_\_\_\_.
the mechanism controlling the appearance of traits was different between the F1 and the F2 plants traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1 members of the F1 generation had only one allele for each trait, but members of the F2 had two alleles for each trait new mutations were frequently generated in the F2 progeny, "reinventing" traits that had been lost in the F1
traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1
127
Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?
One allele was dominant. Each allele affected phenotypic expression. No genes interacted to produce the parental phenotype. The traits blended together during fertilization.
One allele was dominant.
128
Consider pea plants with the genotypes *GgTt* and *ggtt* . These plants can each produce how many type(s) of gametes?
four ... two two... one one ... one one ... two four ... one
our ... one
129
Which of the following is the best statement of the use of the addition rule of probability?
the probability of producing two or more heterozygous offspring the probability that either one of two independent events will occur the probability that two or more independent events will both occur the likelihood that a trait is due to two or more meiotic events
the probability that either one of two independent events will occur
130
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?
Red shows incomplete dominance over white. Pink is dominant, and red and white are recessive. Red is completely dominant. Both red and white are pleiotropic.
Red shows incomplete dominance over white.
131
Which of the following describes the ability of a single allele to have multiple phenotypic effects?
incomplete dominance multiple alleles epistasis pleiotropy
pleiotropy
132
Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?
the alleles being codominant the knowledge that multiple alleles are involved the allele for blue hydrangea being completely dominant environmental factors such as soil pH
environmental factors such as soil pH
133
Gene *S* controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, *S*, have sharp spines, whereas homozygous recessive *ss* cactuses have dull spines. At the same time, a second gene, *N*, determines whether or not cactuses have spines. Homozygous recessive *nn* cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce\_\_\_\_\_.
50% sharp-spined, 50% dull-spined progeny all sharp-spined progeny 25% sharp-spined, 50% dull-spined, 25% spineless progeny It is impossible to determine the phenotypes of the progeny.
all sharp-spined progeny
134
Folk singer Woody Guthrie died of Huntington's disease, an autosomal dominant disorder. Which statement below must be true?
All of his children will develop Huntington's disease. His sons will develop Huntington's disease but not his daughters. His daughters will die of Huntington's disease but not his sons. It is very likely that at least one of Woody Guthrie's parents also have had the allele for Huntington's disease. There is not enough information to answer the question.
It is very likely that at least one of Woody Guthrie's parents also have had the allele for Huntington's disease.
135
In some parts of Africa, the frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?
the malarial parasite changing the allele Darwin's explanation of natural selection Mendel's law of segregation Mendel's law of independent assortment
Darwin's explanation of natural selection
136
**If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring will be cross-eyed? Express your answer using the percent symbol and no spaces (for example, 10%).**
25%
137
What percentage of cross-eyed tigers will be white? Express your answer using the percent symbol and no spaces (for example, 10%).
100%
138
```
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```
Consider the following family history:
Bob has a genetic condition that affects his skin.
Bob’s wife, Eleanor, has normal skin. No one in Eleanor’s family has ever had the skin condition.
Bob and Eleanor have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their daughters have the same skin condition as Bob.
**Based on Bob and Eleanor’s family history, what inheritance pattern does the skin condition most likely follow?**
X-linked recessive
Y-linked
autosomal recessive
X-linked dominant
autosomal dominant
X-linked dominant
139
In humans, what determines the sex of offspring and why?
```
```
The female gamete determines sex because only the female gametes can have one of two functional sex chromosomes.
The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome.
The male determines sex because the sperm can fertilize either a female egg or a male egg.
The female gamete determines sex because only the female gamete provides cytoplasm to the zygote.
The chromosome contribution from both parents determines sex because the offspring uses all the parents' chromosomes.
```
```
## Footnote
The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome.
140
Which of the following is true of an X-linked gene, but not of a Y-linked gene?
```
```
It is only expressed in female offspring.
The gene is present in both males and females.
Sister chromatids separate during mitosis.
It does not segregate like other genes.
It is expressed in half of the cells of either male or female.
```
```
## Footnote
The gene is present in both males and females.
141
Males are more often affected by sex-linked traits than females because \_\_\_\_\_.
```
```
male hormones such as testosterone often alter the effects of mutations on the X chromosome
X chromosomes in males generally have more mutations than X chromosomes in females
female hormones such as estrogen often compensate for the effects of mutations on the X chromosome
males are hemizygous for the X chromosome
```
```
## Footnote
males are hemizygous for the X chromosome
142
Normally, only female cats have the tortoiseshell phenotype because \_\_\_\_\_.
```
```
a male inherits only one allele of the X-linked gene controlling hair color
the Y chromosome has a gene blocking orange coloration
only males can have Barr bodies
multiple crossovers on the Y chromosome prevent orange pigment production
```
```
## Footnote
a male inherits only one allele of the X-linked gene controlling hair color
143
In humans, clear gender differentiation occurs, not at fertilization, but after the second month of gestation. What is the first event of this differentiation?
```
```
formation of testosterone in male embryos
activation of *SRY* in females and feminization of the gonads
activation of *SRY* in male embryos and masculinization of the gonads
formation of estrogens in female embryos
```
```
## Footnote
activation of *SRY* in male embryos and masculinization of the gonads
144
In birds, sex is determined by a ZW chromosome scheme that is much like the typical XY scheme seen in humans and many other organisms, except that the system is reversed: Males are ZZ (similar to XX in humans) and females are ZW (similar to XY in humans). A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female?
```
```
1:2 male to female
1:1 male to female
2:1 male to female
3:1 male to female
```
```
## Footnote
2:1 male to female
145
In general, the frequency with which crossing over occurs between two linked genes depends on what?
```
```
whether the genes are dominant or recessive
how far apart they are on the chromosome
the characters the genes code for
the phase of meiosis in which the crossing over occurs
whether the genes are on the X or some other chromosome
```
```
## Footnote
how far apart they are on the chromosome
146
Recombination between linked genes comes about for what reason?
```
```
Linked genes travel together at anaphase.
Nonrecombinant chromosomes break and then rejoin with one another.
Independent assortment sometimes fails.
Crossovers between these genes result in chromosomal exchange.
```
```
## Footnote
Crossovers between these genes result in chromosomal exchange.
147
Which of the following results in a situation in which the chromosome number is either 2*n*+1 or 2*n*-1 ?
```
```
methylation
inversion
polyploidy
gene linkage
aneuploidy
```
aneuploidy
```
148
What results if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction?
```
```
a translocation
a deletion
polyploidy
a nondisjunction
an inversion
```
```
## Footnote
an inversion
149
Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel’s law of segregation?
```
```
The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.
The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.
Sister chromatids separate during anaphase II.
```
```
## Footnote
The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.
150
Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel’s law of independent assortment?
```
```
Sister chromatids separate during anaphase II.
The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.
The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.
```
```
## Footnote
The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.
151
Select the correct statement(s) about sex determination in animals.
**Select all that apply.**
```
```
The mechanism of sex determination varies with different animal species.
In all animals, males have the *SRY* gene and females lack this gene.
In all animals, males are XY and females are XX.
```
```
## Footnote
The mechanism of sex determination varies with different animal species.
152
Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females?
```
```
Males and females would display this disorder with equal frequency.
Males would display this disorder with greater frequency than females.
Females would display this disorder with greater frequency than males.
```
```
## Footnote
Females would display this disorder with greater frequency than males.
153
