Chapter 11
Which of the following is likely to occur in E. coli cells that are grown in skim milk? A) The lac operon is shut off, and the cells will not produce lactose-utilizing enzymes. B) The trp repressor is activated, and the cells will produce lactose-utilizing enzymes. C) The trp operon is turned on, but the bacteria will not produce lactose-utilizing enzymes. D) The trp operon and the lac operon are both switched off.
B
A gene that can cause cancer when present in a single copy in a cell is called a(n) A) oncogene. B) enhancer gene. C) carcinogen. D) proto-oncogene.
a
A single cell, the zygote, can develop into an entirely new organism with many different specialized cells. Which of the following statements about this process is false? A) Additional genetic information for the formation of specialized cells is passed on to the developing embryo via the mother. B) The descendant cells specialize by a process known as differentiation. C) The zygote contains all of the genetic information required for the development of many different cell types. D) Differentiation of the zygote into a multicellular organism results from selective gene expression.
a
E. coli can synthesize the amino acid threonine or absorb it from the environment. In the thr operon, the repressor is active when it is bound to threonine. If an E. coli bacterium is in an environment where threonine is absent, will transcription of threonine synthesis genes take place? Why or why not? A) Yes, because threonine will not be bound to the repressor, so the repressor will be inactive. B) No, because threonine will not be bound to the repressor, so the repressor will be inactive. C) Yes, because threonine will not be bound to the repressor, so the repressor will be active. D) No, because threonine will not be bound to the repressor, so the repressor will be active.
a
In thinking about their role in cell division, oncogenes are like the ________ of a car, while tumor suppressor genes are like the ________ of a car. A) gas pedal; brakes B) steering wheel; brakes C) gas pedal; headlights D) brakes; gas pedal
a
Small pieces of RNA that can regulate translation of mRNA are called A) microRNA. B) interfering RNA. C) transfer RNA. D) messenger RNA.
a
The cloning of Dolly the sheep A) demonstrated that the nuclei from differentiated mammalian cells can retain their full genetic potential. B) demonstrated that differentiated cells contain only a fraction of their full genetic potential. C) demonstrated, for the first time, that eggs are haploid and body cells are diploid. D) revealed that cloned mammals most resemble the egg donor.
a
The genes for the enzymes of glycolysis A) are active in all metabolizing cells, but the genes for specialized proteins are expressed only in particular cell types. B) are inactive in all metabolizing cells, but the genes for specialized proteins are expressed in all cell types. C) and the genes for all specialized proteins are expressed in all metabolizing cells. D) and the genes for all specialized proteins are expressed in all embryonic cells.
a
The lac operon in Escherichia coli A) prevents lactose-utilizing enzymes from being expressed when lactose is absent from the environment. B) prevents lactose intolerance. C) prevents lactose-utilizing enzymes from being expressed when lactose is present in the environment. D) promotes the expression of lactose-utilizing enzymes when lactose is absent from the environment.
a
The lac operon of E. coli is ________ when the repressor is bound to lactose. A) active B) inactive C) cloned D) unregulated
a
There is a mutation in the operator of the trp operon in a cell such that the trp repressor is unable to bind to the operator. If tryptophan is added to the cell, what will happen? A) Tryptophan will bind to the repressor, and trp enzymes will be produced. B) Tryptophan will bind to the repressor, and trp enzymes will not be produced. C) Tryptophan will not bind to the repressor, and trp enzymes will be produced. D) Tryptophan will bind to the operator, and trp enzymes will be produced.
a
Transcription factors attach to A) DNA. B) signal molecules. C) plasma membrane receptors. D) mRNA.
a
A homeotic gene A) determines which end of the egg will become the head and which end will become the tail. B) serves as a master control gene that functions during embryonic development by controlling the developmental fate of groups of cells. C) represses gene transcription and promotes mRNA translation. D) is found only in adult somatic cells.
b
A normal muscle cell produces the myosin protein, which allows muscles to contract. You discover a single muscle cell that has tRNAs that do not bind to amino acids. Will the myosin gene be expressed in this muscle cell? Why or why not? A) Yes, because all cells in the body express the myosin gene all of the time. B) No, because if the tRNAs do not bind amino acids, then translation cannot occur. C) Yes, because the myosin gene will be transcribed in the muscle cell nucleus. D) No, because the myosin mRNA will likely get broken down in the cytoplasm.
b
A signal outside a cell triggers changes in the transcription and translation inside the cell through A) post-translational editing. B) signal transduction pathways. C) protein activation. D) protein breakdown.
b
A stomach cell is producing pepsin, an enzyme that hydrolyzes proteins. Which of the following events suggests that gene expression of pepsin has been turned off in the cell? A) The pepsin protein is folded properly in the cytoplasm. B) The chromosome with the pepsin gene is tightly coiled. C) The pepsin mRNA leaves the nucleus and enters the cytoplasm. D) Activators and RNA polymerases are abundant in the nucleus.
b
Cancer of the colon is caused by A) a single somatic cell gene mutation. B) several somatic cell gene mutations. C) a physical rupture of the colon. D) a diet high in fiber and low in fat.
b
During an experiment assessing the development of a fly embryo, a scientist artificially turns on a homeotic gene that controls eye development in somatic cells that develop into the wings. Which of the following is the most likely outcome of this experiment? A) A normal adult fly will develop. B) A mutant adult fly will develop that has eyes on its wings. C) A mutant adult fly will develop that has legs on its head. D) A mutant adult fly will develop that has no eyes on its head but has eyes on its wings.
b
In 2013, an estimated 160,000 people in the United States will die of lung cancer. If the cancer death rate is expected to increase by 1% per decade, approximately how many people will die of lung cancer in the United States in 2033? A) 160,000 B) 163,000 C) 176,000 D) 194,000
b
In a prokaryote, a group of genes with related functions, along with their associated control sequences, defines A) an allele. B) an operon. C) a locus. D) a transposon.
b
Mutations in the p53 gene can lead to cancer by A) causing the production of excessive amounts of relay proteins. B) causing the production of a faulty protein that is no longer able to inhibit cell division. C) promoting the expression of mRNA that can interact with DNA, resulting in new mutations. D) increasing the production of growth hormones, which trigger faster cell cycles.
b
Scientists are attempting to make a chicken look like a dinosaur ("dino-chicken") by using drugs or proteins to turn on certain homeotic genes during the development of a chicken embryo. If the scientists are successful in creating both male and female "dino-chickens," and then the "dino-chickens" mate together, what type of offspring would the two "dino-chickens" have? A) a male or female "dino-chicken" B) a male or female normal chicken C) You can't know for sure because of random fertilization. D) You can't know for sure because it depends on whether the modified homeotic genes are dominant or recessive.
b
The basis of cellular differentiation is A) the operon. B) selective gene expression. C) cloning. D) mutation.
b
The coding regions of a gene are called A) introns. B) exons. C) promoters. D) enhancers.
b
The development of colon cancer occurs slowly, and colon cancer is more frequently seen in the elderly than the young. This is most likely because A) cancer cells don't have mitochondria, so they grow slowly. B) usually six or more somatic mutations must occur to give rise to the cancer, which takes time. C) cancer cells have to wait until new blood vessels grow into the area, which takes much time. D) most cancer mutations interfere with mitosis, so cell division occurs more slowly.
b
There is a mutation in the operator of the lac operon in a cell such that the lac repressor always stays bound to the operator. If lactose is added to the cell, what will happen? A) Lactose will bind to the repressor, and lac enzymes will be produced. B) Lactose will bind to the repressor, and lac enzymes will not be produced. C) Lactose will not bind to the repressor, and lac enzymes will be produced. D) Lactose will bind to the operator, and lac enzymes will be produced.
b
To initiate a signal transduction pathway, a signal binds to a receptor protein usually located in the A) nucleus. B) plasma membrane. C) ER. D) cytoplasm.
b
What is the proper order of events in the expression of a eukaryotic protein? A) DNA unpacking, mRNA transport through nucleus, mRNA splicing, protein modification B) DNA unpacking, mRNA splicing, translation, protein folding C) transcription, translation, addition of cap and tail to mRNA, DNA unpacking D) transcription, mRNA splicing, protein modification, translation
b
Which of the following mammals has not yet been cloned and brought through the complete gestation cycle? A) cow B) human C) pig D) cat
b
Which of the following permits a single gene to code for more than one polypeptide? A) retention of different introns in the final version of the different mRNA strands B) alternative RNA splicing C) genetic differentiation D) addition of different types of caps and tails to the final version of the mRNA strands
b
Which of the following processes occurs when a salamander regenerates a lost limb? A) The homeotic genes of the regenerating limb are expressed. B) Certain cells in the limb dedifferentiate, divide, and then redifferentiate to form a new limb. C) A new salamander develops from the lost limb. D) The homeotic genes of the regenerating cells turn off.
b
Which of the following statements about fruit fly development is false? A) One of the earliest development events is the determination of the head and tail ends of the egg. B) The location of the head and tail ends of the egg is primarily determined by the location of sperm entry during fertilization. C) Homeotic genes regulate batteries of other genes that direct the anatomical identity of body parts. D) Cascades of gene expression routinely direct fruit fly development.
b
Which of the following statements about microarrays is false? A) Microarrays enable scientists to determine the activity of thousands of genes at once. B) Microarrays use tiny portions of double-stranded RNA fragments from a large number of genes. C) Microarrays are used to determine which genes are active in different tissues or in tissues of different states of health. D) Microarrays use fluorescently labeled cDNA molecules to identify particular genes expressed at a particular time.
b
Which of the following statements regarding DNA packing is false? A) A nucleosome consists of DNA wound around a protein core of eight histone molecules. B) DNA packing tends to promote gene expression. C) Highly compacted chromatin is generally not expressed at all. D) Prokaryotes have proteins analogous to histones.
b
Which of the following statements regarding cancer risk factors is false? A) Factors that alter DNA and make cells cancerous are called carcinogens. B) Mutagens are usually not carcinogens. C) X-rays and ultraviolet radiation are two of the most potent carcinogens. D) Eating 20-30 grams of plant fiber daily and reducing the intake of animal fat can reduce your risk of developing colon cancer.
b
Which of the following statements regarding stem cells is false? A) Embryonic stem cells can give rise to all the different specialized cells in the body. B) Adult, but not embryonic, stem cells can be grown in laboratory culture. C) Adult stem cells are present in adult tissues. D) Adult stem cells are partway along the road to differentiation.
b
Why can some plants be cloned from a single cell? A) Plant cells do not differentiate even when mature, so any cell can grow into an entire plant. B) Plant cells can dedifferentiate and give rise to all of the specialized cells required to produce an entire plant. C) Plant cells can produce genes to replace those lost during development. D) Plant cells are capable of self-renewal by utilizing cellular components from adjacent cells.
b
Yeast are able to communicate with each other A) by close cell-to-cell contact. B) through chemical signaling. C) only if they can touch each other and have merged cell walls. D) with pseudopodia.
b
All of the following mechanisms are used to regulate protein production except A) protein activation. B) protein breakdown. C) DNA replication. D) the breakdown of mRNA.
c
Both prokaryotic and eukaryotic cells use ________ to turn certain genes on or off. A) RNA transcriptase B) intron segments C) proteins D) nucleosome packing
c
Enhancers are A) adjacent to the gene that they regulate. B) required to turn on gene expression when transcription factors are in short supply. C) DNA sequences to which activator proteins bind. D) required to facilitate the binding of DNA polymerases.
c
In plants, most differentiated cells retain A) only a tiny fraction of their original set of genes. B) a complete set of their genes but lose the ability to express most of those genes. C) a complete set of their genes and retain the ability to express those genes under certain circumstances. D) the ability to dedifferentiate but then cannot return to their original differentiated state.
c
Proteins that bind to DNA and turn on operons by making it easier for RNA polymerase to bind to a promoter are called A) regulators. B) operators. C) activators. D) repressors.
c
RNA splicing involves the A) addition of a nucleotide "cap" to the molecule. B) addition of a nucleotide "tail" to the molecule. C) removal of introns from the molecule. D) removal of exons from the molecule.
c
The expression of the tryptophan operon is controlled by A) a repressor that is active when it is alone. B) a repressor that is inactive when it binds to lactose. C) a repressor that is active when it binds to tryptophan. D) an activator that turns the operon on by binding to DNA.
c
The relationship between DNA and chromosomes is most like A) an egg yolk inside of an egg. B) a spoon cradling some peas. C) thread wrapped around a spool. D) the candy shell surrounding the chocolate in a piece of M&M candy.
c
The term "gene expression" refers to the A) fact that each individual of a species has a unique set of genes. B) fact that individuals of the same species have different phenotypes. C) process by which genetic information flows from genes to proteins. D) flow of information from parent to offspring.
c
The tortoiseshell pattern on a cat A) usually occurs in males. B) is the result of a homozygous recessive condition. C) results from X chromosome inactivation. D) is a result of alleles on the Y chromosome.
c
Two yeast cells, one of type a and the other type α, are in proximity to each other. The a yeast cell has a mutation in the gene for the α factor receptor protein such that the receptor does not translocate to the surface of the a cell. If both cells secrete their respective a and α factors, which of the following outcomes is most likely to occur? A) The a and α cells will grow toward each other. B) The a cell will grow towards the α cell. C) The α cell will grow toward the a cell. D) The a and α cells will not grow toward each other at all.
c
Which of the following is not a factor that contributes to normal cells becoming cancerous? A) the conversion of a proto-oncogene to an oncogene B) damage to a tumor-suppressor gene C) the production of more effective tumor-suppressor gene products D) excessive replication of proto-oncogenes
c
A cell has a mutation in both alleles of its p53 gene that causes the p53 protein to be three times as effective as normal. What do you predict would happen to this cell? A) The cell would divide three times as fast and would lead to cancer. B) The cell would divide into six daughter cells instead of two and would lead to cancer. C) The cell would divide with mutated DNA and would lead to cancer. D) The cell would divide normally or possibly not at all.
d
A cell is expressing the mutant form of ras, but one of the downstream relay proteins is not present because of another mutation. How will cell division be affected in this scenario? A) Cell division will decrease because the mutant form of ras decreases cell division. B) Cell division will increase because the mutant form of ras increases cell division. C) The cell will divide normally. D) The cell will not divide at all unless other proteins that stimulate cell division are present.
d
A gene operon consists of A) a transcribed gene only. B) a promoter only. C) a regulatory gene only. D) transcribed genes, an operator, and a promoter.
d
Adult stem cells have limited therapeutic potential A) because they are fully differentiated. B) because they lack a complete set of genes. C) due to their excessive numbers in tissues. D) because their developmental potential is limited to certain tissues.
d
In female mammals, the inactive X chromosome in each cell A) can be activated if mutations occur in the active X chromosome. B) is broken down, and its nucleotides are degraded and reused. C) is absorbed and used in energy production. D) becomes a Barr body.
d
In multicellular organisms, the coordination of cellular activities relies on A) cell receptors that detect transcription factors. B) the availability of certain "key" nutrients as cells divide. C) operons. D) cell-to-cell signaling and signal transduction pathways.
d
In terms of gene regulation, what do eukaryotes and prokaryotes have in common? A) operons such as the lac operon and the trp operon B) elaborate packing of DNA into chromosomes C) activator proteins that bind to DNA D) promoters that bind RNA polymerases
d
Melanoma (skin cancer) can develop after several mutations occur in skin cells. If a woman is diagnosed with melanoma and becomes pregnant, what are the chances that her offspring will inherit melanoma? A) The offspring will certainly be born with melanoma. B) There is a chance, but it depends on how serious the mother's melanoma is. C) There is a chance, but it depends on whether or not the father has melanoma. D) It is unlikely that the offspring will be born with melanoma.
d
Mutations in the proto-oncogene ras and the tumor suppressor gene p53 A) increase protein synthesis by the cell. B) can improve the chance of avoiding cancer as one ages. C) can enhance further mutations, which can develop into cancer. D) disrupt normal regulation of the cell cycle.
d
RNA interference (RNAi) can be used by A) researchers to induce the production of more mRNA. B) researchers to artificially turn on gene expression. C) viruses to stop the production of new proteins. D) cells to prevent infections from double-stranded RNA viruses.
d
Signal transduction pathways A) are found strictly in multicellular organisms which require cell-to-cell communication. B) are limited for use in sexual identification. C) originally evolved in vertebrates. D) are mechanisms of communication that probably evolved in ancient prokaryotes.
d
The carcinogen known to cause the most cases and types of cancer is A) X-rays. B) ultraviolet light. C) alcohol. D) tobacco.
d
The use of cloning to produce special embryonic stem cells is called A) regenerative cloning. B) transplantational cloning. C) reproductive cloning. D) therapeutic cloning.
d
There is a mutation in a promoter next to a gene such that RNA polymerase can never bind. What steps must occur for the gene to be transcribed? A) An activator protein must bind an enhancer. B) The DNA must physically bend so that the activator is close to the promoter. C) Transcription factors must bind to the activator and promoter. D) Transcription will never take place in this specific example.
d
What is the correct order of structures in a chromosome from smallest to largest? A) nucleotide, nucleosome, histone, supercoil, tight helical fiber, chromosome B) nucleosome, nucleotide, histone, tight helical fiber, supercoil, chromosome C) nucleotide, histone, tight helical fiber, nucleosome, chromosome, supercoil D) nucleotide, histone, nucleosome, tight helical fiber, supercoil, chromosome
d
Which of the following mechanisms of controlling gene expression occurs outside of the nucleus? A) adding a cap and tail to RNA B) DNA packing/unpacking C) RNA splicing D) translation
d
Which of the following molecules are not required to express a gene in eukaryotic cells? A) RNA polymerase B) DNA-bending protein C) activator protein D) repressor protein
d
Which of the following possible uses of reproductive cloning is still considered by most to be an unresolved ethical issue? A) the production of genetically identical animals for experimentation B) cloning mammals for the production of potentially valuable drugs C) the production of organs in cloned pigs for transplant into humans D) the reproductive cloning of humans
d
Which of the following statements about proto-oncogenes is false? A) Proto-oncogenes are normal genes with the potential to become oncogenes. B) Many proto-oncogenes code for growth factors. C) A mutation must occur in a cell's DNA for a proto-oncogene to become an oncogene. D) If a proto-oncogene's gene product is produced in smaller quantities, a cell may become cancerous.
d
Which of the following statements regarding skin cells and muscle cells in your body is true? A) Muscle cells contain information about muscle proteins but not about skin color. B) Skin cells contain information skin color but not about muscle proteins. C) Muscle cells contain information about skin color but not about muscle proteins. D) Skin cells and muscle cells each contain information about both muscle proteins and skin color.
d
