Life 120 Exam 4
What is the proper order of the following events in the expression of a eukaryotic gene? 1. translation 2. RNA processing 3. transcription 4. modification of protein 2, 3, 4, 1 1, 2, 3, 4 4, 2, 3, 1 3, 2, 1, 4 1, 2, 4, 3
3, 2, 1, 4
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following? -The same codons in different organisms translate into the different amino acids. -A gene from an organism can theoretically be expressed by any other organism. -DNA was the first genetic material. -Different organisms have different numbers of different types of amino acids. -All organisms have experienced convergent evolution.
A gene from an organism can theoretically be expressed by any other organism.
Embryonic lethal mutations result in A) phenotypes that are never born/hatched. B) failure to express maternal effect genes. C) phenotypes that prevent fertilization. D) death during pupation. E) homeotic phenotype changes.
A) phenotypes that are never born/hatched.
If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then A) the amino acid acts as a corepressor. B) the enzymes produced are called inducible enzymes. C) the amino acid inactivates the repressor. D) the amino acid turns on transcription of the operon. E) the repressor is active in the absence of the amino acid.
A) the amino acid acts as a corepressor.
The product of the bicoid gene in Drosophila provides essential information about A) the anterior-posterior axis. B) lethal genes. C) segmentation. D) the dorsal-ventral axis. E) the left-right axis.
A) the anterior-posterior axis.
Post-transcriptional controls __________. may regulate the rate at which a molecule is translated can affect mRNA stability can include translational controls can regulate mRNA splicing All of the choices are correct.
All of the choices are correct.
Which statement about feedback inhibition is true? -If the end product accumulates in the cell, the whole pathway is shut down by inhibiting enzyme activity. -It allows a cell to adapt quickly to fluctuations in the supply of a substance it needs. -The end product of the metabolic pathway controls the activity of the first enzyme in the pathway. -It is typically found in anabolic (biosynthetic) pathways. -All of the choices are correct.
All of the choices are correct.
Which is a means of controlling eukaryotic gene expression? mRNA processing DNA packing transcriptional regulation methylation of DNA All of the choices play a role in the regulation of gene expression.
All of the choices play a role in the regulation of gene expression.
Which statement regarding the structure and function of tRNA is false? -Each type of tRNA molecule translates a particular mRNA codon into a particular amino acid. -Although each tRNA consists of a relatively short, single RNA strand, this single strand can achieve a three-dimensional structure by folding back upon itself and forming covalent bonds between complementary bases. -The nucleotide sequence at both the amino acid attachment and the anticodon ends of each tRNA is instrumental in specifying which amino acid is attached to the tRNA by aminoacyl-tRNA synthetase. -Although there are 61 codons that code for amino acids, there are only 45 different tRNA molecules. -The second and third choices are false.
Although each tRNA consists of a relatively short, single RNA strand, this single strand can achieve a three-dimensional structure by folding back upon itself and forming covalent bonds between complementary bases.
RNA polymerase moves in which direction along the DNA? A) 3' to 5' along the nontemplate strand B) 3' to 5' along the template strand C) 5' to 3' along the double-stranded DNA D) 5' to 3' along the template strand E) 5' to 3' along whichever strand it's on
B) 3' to 5' along the template strand
In animals, what is the difference between reproductive cloning and therapeutic cloning? A) Reproductive cloning uses totipotent cells, whereas therapeutic cloning does not. B) Therapeutic cloning supplies cells for repair of diseased or injured organs. C) Therapeutic cloning uses nuclei of adult cells transplanted into enucleated nonfertilized eggs. D) Reproductive cloning uses embryonic stem cells, whereas therapeutic cloning does not.
B) Therapeutic cloning supplies cells for repair of diseased or injured organs.
Which of the following statements describes proto-oncogenes? A) They are introduced to a cell initially by retroviruses. B) They can code for proteins associated with cell growth. C) They are produced by somatic mutations induced by carcinogenic substances. D) Their normal function is to suppress tumor growth. E) They are underexpressed in cancer cells.
B) They can code for proteins associated with cell growth.
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is A) TTT. B) UUU. C) either UAA or TAA, depending on first base wobble. D) UUA. E) AAA.
B) UUU.
Which of the following is a function of a signal peptide? A) to bind RNA polymerase to DNA and initiate transcription B) to translocate polypeptides across the ER membrane C) to signal the initiation of transcription D) to terminate translation of the messenger RNA E) to direct an mRNA molecule into the cisternal space of the ER
B) to translocate polypeptides across the ER membrane
Who formulated the one gene-one enzyme hypothesis? Hershey and Chase Franklin Watson and Crick Beadle and Tatum None of the choices is correct.
Beadle and Tatum
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following? A) DNA was the first genetic material. B) The same codons in different organisms translate into the different amino acids. C) A gene from an organism can theoretically be expressed by any other organism. D) All organisms have experienced convergent evolution. E) Different organisms have different numbers of different types of amino acids.
C) A gene from an organism can theoretically be expressed by any other organism.
Which of the following best describes the significance of the TATA box in eukaryotic promoters? A) It is the recognition site for ribosomal binding. B) It prevents supercoiling of the DNA near the start site. C) It is the recognition site for a specific transcription factor. D) Its significance has not yet been determined. E) It sets the reading frame of the mRNA.
C) It is the recognition site for a specific transcription factor.
Why might a point mutation in DNA make a difference in the level of a protein's activity? A) It might substitute the N- terminus of the polypeptide for the C- terminus. B) It might result in a chromosomal translocation. C) It might substitute a different amino acid in the active site. D) It might exchange one stop codon for another stop codon. E) It might exchange one serine codon for a different serine codon.
C) It might substitute a different amino acid in the active site.
In eukaryotes, general transciption factors A) are required for the expression of specific protein- encoding genes. B) inhibit RNA polymerase binding to the promoter and begin transcribing. C) bind to other proteins or to a sequence element within the promoter called the TATA box. D) usually lead to a high level of transcription even without additional specific transcription factors. E) bind to sequences just after the start site of transcription.
C) bind to other proteins or to a sequence element within the promoter called the TATA box.
Transcription in eukaryotes requires which of the following in addition to RNA polymerase? A) ribosomes and tRNA B) aminoacyl-tRNA synthetase C) several transcription factors D) start and stop codons E) the protein product of the promoter
C) several transcription factors
According to the Central Dogma of molecular biology ______________. A)DNA encodes RNA B) RNA encodes protein C) proteins cannot encode genetic information D) All of the above are true.
D) All of the above are true.
Which of the following is an important part of the developmental process in animals? A) induction B) cell migration C) differentiation D) All of the above. E) apoptosis
D) All of the above.
Which of the following is characteristic of the product of the p53 gene? A) It speeds up the cell cycle. B) It allows cells to pass on mutations due to DNA damage. C) It slows down the rate of DNA replication by interfering with the binding of DNA polymerase. D) It is an activator for other genes. E) It causes cell death via apoptosis.
D) It is an activator for other genes.
Which of the following is true of embryonic stem cells but not of adult stem cells? A) They can provide enormous amounts of information about the process of gene regulation. B) They can continue to reproduce for an indefinite period. C) One aim of using them is to provide cells for repair of diseased tissue. D) They can give rise to all cell types in the organism. E) They normally differentiate into only eggs and sperm.
D) They can give rise to all cell types in the organism.
If a Drosophila female has a homozygous mutation for a maternal effect gene, A) only her female offspring will show the mutant phenotype. B) she will not develop past the early embryonic stage. C) her offspring will show the mutant phenotype only if they are also homozygous for the mutation. D) all of her offspring will show the mutant phenotype, regardless of their genotype. E) only her male offspring will show the mutant phenotype.
D) all of her offspring will show the mutant phenotype, regardless of their genotype.
Alternative RNA splicing A) is a mechanism for increasing the rate of transcription. B) is due to the presence or absence of particular snRNPs. C) can allow the production of similar proteins from different RNAs. D) can allow the production of proteins of different sizes and functions from a single mRNA. E) increases the rate of transcription.
D) can allow the production of proteins of different sizes and functions from a single mRNA.
The anticodon of a particular tRNA molecule is A) changeable, depending on the amino acid that attaches to the tRNA. B) complementary to the corresponding triplet in rRNA. C) the part of tRNA that bonds to a specific amino acid. D) complementary to the corresponding mRNA codon. E) catalytic, making the tRNA a ribozyme.
D) complementary to the corresponding mRNA codon.
Apoptosis involves all but which of the following? A) cell-signaling pathways B) digestion of cellular contents by scavenger cells C) activation of cellular enzymes D) lysis of the cell E) fragmentation of the DNA
D) lysis of the cell
Embryonic lethal mutations result in A) homeotic phenotype changes. B) death during pupation. C) failure to express maternal effect genes. D) phenotypes that are never born/hatched. E) phenotypes that prevent fertilization.
D) phenotypes that are never born/hatched.
Suppose you found a Drosophila mutant that has legs coming out of the head instead of antennae. A mutation that caused this phenotype is likely to be found in A.Segment-polarity genes B.Apoptosis regulatory genes C.Morphogen genes D.Homeotic genes E.Egg-polarity genes
D. Homeotic genes
Which of the following statements describes the eukaryotic chromosome? A)It is composed of DNA alone. B) The number of genes on each chromosome is different in different cell types of an organism. C) Active transcription occurs on heterochromatin but not euchromatin. D) The nucleosome is its most basic functional subunit. E) It consists of a single linear molecule of double-stranded DNA plus proteins.
E) It consists of a single linear molecule of double-stranded DNA plus proteins.
In colorectal cancer, several genes must be mutated in order to contribute to a cell developing into a cancer cell, supporting Knudsen's hypothesis. Which of the following kinds of genes would you expect to be mutated? A) the genes of the bacteria that are abundant in the colon B) genes coding for enzymes that act in the colon C) genes that are especially susceptible to mutation D) the same genes that Knudsen identified as associated with retinoblastoma E) genes involved in control of the cell cycle
E) genes involved in control of the cell cycle
Mutations in which of the following genes lead to transformations in the identity of entire body parts? A) inducers B) morphogens C) egg-polarity genes D) segmentation genes E) homeotic genes
E) homeotic genes
Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene A) is a protein present in all head structures. B) normally leads to formation of tail structures. C) is transcribed in the early embryo. D) leads to programmed cell death. E) normally leads to formation of head structures.
E) normally leads to formation of head structures.
Which of the following is most closely identical to the formation of twins? A) embryo transfer B) cell cloning C) therapeutic cloning D) use of adult stem cells E) organismal cloning
E) organismal cloning
Which statement about gene expression is true? -Each amino acid in a protein is coded for by three DNA bases. -Each gene codes for three proteins. -Each DNA base codes for three amino acids. -Each triplet has many different meanings. -It takes three genes to code for one protein.
Each amino acid in a protein is coded for by three DNA bases.
Which accurately describes the usual process of transcription for eukaryotic genes? -Both introns and exons are transcribed, but the RNA transcribed from them does not leave the nucleus. -Exons are not transcribed. -Exons and introns are transcribed, and the RNA transcribed from them leaves the nucleus. -Introns are not transcribed. -Exons are transcribed, but the RNA transcribed from introns does not leave the nucleus.
Exons are transcribed, but the RNA transcribed from introns does not leave the nucleus. The noncoding elements that lie between coding regions, called introns, are spliced out of the mRNA during processing. The pre-mRNA never leaves the nucleus; only the processed message enters the cytoplasm for translation.
A cell biologist found that two different proteins with largely different structures were translated from two different mRNAs. These mRNAs, however, were transcribed from the same template within the cell nucleus. Which mechanism could best account for this? -The two proteins have different functions in the cell. -Different transcription factors were involved in the transcription of the two mRNAs. -Different systems of DNA unpacking could result in two different mRNAs. -A point mutation might have altered the gene. -Exons from the same gene could be spliced in different ways to make different mRNAs.
Exons from the same gene could be spliced in different ways to make different mRNAs.
Which best describes the makeup of the human genome? -Genes for noncoding RNA make up the majority of meaningful genetic information in the human genome. -Most of the genome does not contain meaningful genetic --information and is not transcribed. -Most of the genome consists of protein-coding DNA. -The amount of DNA that consists of genes for ribosomal RNA and transfer RNA is slightly greater than the protein-coding DNA. -None of the choices is correct.
Genes for noncoding RNA make up the majority of meaningful genetic information in the human genome.
Which statement about transcription is false? -A relaxation of chromatin packing in eukaryotic cells can facilitate the binding of transcription factors to a promoter of a gene -In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes. -The initiation of gene transcription in eukaryotes requires the binding of proteins called transcription factors to the TATA box in the promoter region of a gene. -In bacteria, transcription of a gene is initiated when the RNA polymerase by itself recognizes and binds to the promoter of the gene. -All of the choices are correct
In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes. This statement is false. Transcription factors are required to initiate transcription in eukaryotes. In bacteria, the RNA polymerase alone can bind to the promoter site of a gene.
What is a key difference in gene expression between eukaryotic and prokaryotic cells? -In prokaryotes, proteins are assembled directly from DNA. -Prokaryotes do not contain ribosomes. -RNA polymerases are involved only in initiation in eukaryotes. -In eukaryotic cells, transcribed RNA sequences function as termination signals. -In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing.
In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing. In the absence of a nucleus, it can simultaneously transcribe and translate the same gene.
What is the evolutionary significance of alternative RNA splicing? -The introns that are spliced out can become miRNAs and can recognize and degrade mRNA transcripts. -Because it is not specific to a cell type, alternative RNA splicing can make sweeping changes in gene expression, allowing an organism to adapt quickly to new situations. -It expands the number of proteins that can be coded for by one gene, increasing an organism's ability to produce novel proteins. -It can silence genes, giving cells another way of controlling gene expression. -It acts as a defense against viral RNA, helping organisms avoid infection, particularly by cancer-causing viruses.
It expands the number of proteins that can be coded for by one gene, increasing an organism's ability to produce novel proteins.
The P site of a ribosome does what? -It helps "unzip" DNA during transcription. -It catalyzes the addition of amino acids to the tRNAs. -It holds the tRNA that is carrying the next amino acid to be added to the growing polypeptide chain. -It holds the tRNA carrying the growing polypeptide chain. -It recognizes the promoter during transcription initiation.
It holds the tRNA carrying the growing polypeptide chain
This chapter contains a lengthy discussion of the trp operon involved in regulating the synthesis of the amino acid tryptophan. In the case of E. coli, the bacterium may need to synthesize tryptophan, or its host, a human, may supply all the tryptophan it needs. Why do both bacteria and humans need tryptophan? It is an important enzyme in the glycolysis pathway. Tryptophan induces the lac operon. It is one of the 20 amino acids used by all organisms to synthesize proteins. It is an important constituent of cell walls in both humans and bacteria. It is important in inducing sleep.
It is one of the 20 amino acids used by all organisms to synthesize proteins.
Which of the following best describes the significance of the TATA box in eukaryotic promoters? It is the recognition site for a specific transcription factor. Its significance has not yet been determined. It is the recognition site for ribosomal binding. It sets the reading frame of the mRNA. It prevents supercoiling of the DNA near the start site.
It is the recognition site for a specific transcription factor.
Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of __________. lipids DNA proteins RNA carbohydrates
RNA
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? -primase -RNA polymerase I -RNA polymerase III -ligase -RNA polymerase II
RNA polymerase II
In eukaryotes, which mechanism of gene regulation operates after transcription, but before translation of mRNA into protein? -RNA splicing -DNA packaging into nucleosomes -protein degradation -action of repressors and activators -All of the choices are correct.
RNA splicing Introns are deleted and exons are spliced together after transcription and before translation.
Which summary of protein synthesis is correct? -DNA transposons leave the nucleus, are transported to a ribosome, and catalyze the polymerization of amino acids in a protein. -The tRNA's line up on a ribosome, and amino acids bind to them with hydrogen bonds. -DNA strands separate in the nucleus to form mRNA. mRNA leaves the nucleus and is transcribed into tRNA on ribosomes. -The mRNA is made on a DNA template, and then amino-acid-bearing tRNA's bind to it through codon-anticodon pairing. -DNA exchanges its thymine units with uracil (U) in polymerase. This activates polymerase, and it starts joining amino acids together.
The mRNA is made on a DNA template, and then amino-acid-bearing tRNA's bind to it through codon-anticodon pairing.
A high rate of gene transcription in eukaryotic cells is usually dependent on __________. -the binding of general transcription factors to the TATA box within the promoter of a gene -the coordinated control of genes within operons -specific binding of activator molecules to enhancers -protein-protein interactions that are promoted by the activation domains of activator proteins -The third and fourth choices are correct.
The third and fourth choices are correct.
Which describes the arrangement of genetic information in a DNA molecule? -The three-nucleotide words of a gene are serially arranged on both strands of DNA at a specific locus. -By analyzing the linear order of amino acids in a polypeptide, the exact order of the three-nucleotide words of a gene arranged on the template strand of DNA can be determined. -By overlapping the three-nucleotide words of a gene, the amount of information a DNA molecule can hold is maximized. -A gene is composed of overlapping, three-nucleotide words on a template strand of DNA. -The three-nucleotide words of a gene are arranged in a non-overlapping series on the DNA template strand.
The three-nucleotide words of a gene are arranged in a non-overlapping series on the DNA template strand
A geneticist found that a particular mutation had no effect on the polypeptide encoded by the gene. This mutation probably involved __________ a missense mutation a silent or neutral mutation a nonsense mutation the deletion of one nucleotide the insertion of one nucleotide
a silent or neutral mutation
The Drosophila bicoid protein determines ________. a. the anterior-posterior axis of the embryo. b. the ventral-lateral axis of the embryo c. the medial-lateral axis of the embryo d. the number of segments in the embryo e. the sex of the animal
a. the anterior-posterior axis of the embryo.
In transcription, __________. -the promoter region acts as an initial binding site for RNA polymerase -only one of the DNA strands is used as the template -the RNA nucleotides used are produced by the cell -All of the choices above are correct. -None of the choices above is correct.
all of the choices above are correct
You have inserted the gene for a human growth factor into the E. coli lactose operon, replacing the structural genes with the gene for human growth factor. What substance must you add to your culture of bacteria to cause them to produce human growth factor for you? repressor protein operator protein transcription factors allolactose human growth factor
allolactose Allolactose will bind to the repressor protein, inactivating it, and allowing transcription of the genes in the operon, including human growth factor.
Although the number of genes in the human genome is surprisingly low compared to less complex organisms, the number of possible products from those genes is greatly amplified by __________. -alternate arrangements of exons from a primary transcript -differential activation of genes in different cell types -coordinate control of genes on different chromosomes -each gene being activated by a unique combination of control elements and activator molecules -the congregation in specific sites in the nucleus of genes involved in related metabolic processes, but on different chromosomes
alternate arrangements of exons from a primary transcript
In prokaryotic genomes, groups of functionally related genes along with their promoters and operators are found together in __________ a regulatory gene an operon a transcription factor a repressor an enhancer
an operon
Transcription factors are found in __________. archaea eukaryotes bacteria and eukaryotes archaea and eukaryotes bacteria and archaea right answer feedback:
archaea and eukaryotes
How many nucleotides are needed to code for a protein with 450 amino acids? -at least 150 -at least 300 -at least 450 -at least 900 -at least 1,350
at least 1,350 Because the code is a triplet, and three nucleotides code for the incorporation of one amino acid, 450 x 3, or at least 1,350, would be needed.
When is a cell considered completely differentiated? a. When the cell begins pattern formation. b. When the cell synthesizes proteins that are specific to a particular cell type. c. When the cell is part of recognizable tissues or organs. d. When the cell reaches the correct destination in the body.
b. When the cell synthesizes proteins that are specific to a particular cell type.
A drosophila mutant that failed to produce a functional bicoid protein would be expected to have larvae with ________________. a. no head and no tail b. two tails c. two heads d. None of the above.
b. two tails
Which of the following processes provides the foundation for differentiation of a single celled zygote into a multicellular adult. a. apoptosis b. morphogenesis c. expression of a cascade of transcription factors d. cell migration e. All of the above.
c. expression of a cascade of transcription factors
The fact that different kinds of cells in an individual have the same genes, and therefore any cell should have the potential to generate a genetically identical, complete new organism (clone) refers to which of the following concepts? a. pleuripotency b. determination c. totipotency d. morphogenesis e. multipotency
c. totipotency
Ultraviolet (UV) radiation is damaging to cells because it __________. pokes holes in the nuclear envelope deactivates the enzymes needed for DNA replication blocks all translation causes mutations in the DNA shreds the cytoskeleton and leads to free radicals
causes mutations in the DNA
A scientist clones a regulatory gene that is involved in controlling the expression of other genes, and discovers that the regulatory gene encodes a histone deacetylase enzyme. It is likely that this enzyme regulates gene expression by __________. -causing tighter packing of the chromatin at the target gene, thereby enhancing transcription -causing looser packing of the chromatin at the target gene, thereby enhancing transcription -causing tighter packing of the chromatin at the target gene, thereby inhibiting transcription -causing looser packing of the chromatin at the target gene, thereby inhibiting transcription -causing tighter packing of the chromatin at the target gene, thereby inhibiting translation
causing tighter packing of the chromatin at the target gene, thereby inhibiting transcription Deacetylation increases the positive charges on histones, allowing them to bind more tightly to DNA.
A bacterium can make the amino acid glycine or absorb it from its surroundings. A biochemist finds that glycine binds to a repressor protein and causes the repressor to bind to the bacterial chromosome, turning off an operon. If it is like other similar operons, the presence of glycine will result in the __________. breakdown of glycine inhibition of bacterial cell division cessation of the synthesis of glycine formation of sex pili production of the repressor protein
cessation of the synthesis of glycine
Which is a post-translational modification of a polypeptide? -The growing polypeptide signals the ribosome to attach to the ER. removal of introns and splicing of exons -complementary base pairing of mRNA and tRNA in the ribosome -formation of a polysome that allows simultaneous formation of many polypeptides from one mRNA transcript -cleavage of a polypeptide into two or more chains
cleavage of a polypeptide into two or more chains
n eukaryotes, DNA packing seems to affect gene expression primarily by __________. protecting DNA from mutations enhancing the recombination of genes controlling access to DNA positioning related genes near each other allowing unpacked genes to be eliminated from the genome right answer feedback:
controlling access to DNA
It has been possible to regenerate sheep and other mammals using the nucleus/genome of a differentiated cell, but which of the following has been an essential part of the experimental approach? a. The nucleus must be transferred to the cytoplasm of the same type of differentiated cell. b. Epigenetic marks in the nucleus must be removed. c. The nucleus must be striped of proteins. d. The nucleus must be transferred to the cytoplasm of an egg or pleuripotent cell. e. All of the above are true.
d. The nucleus must be transferred to the cytoplasm of an egg or pleuripotent cell.
Early in development, the fate of a cell is determined by ______________ deposited by the mother in the egg, but later in development it is influence by the cell's location and is influenced by positional information communicated by _______________. a. nuclear factors; transcription factors b. cytoplasmic determinants; induction factors c. nuclear factors; cytoplasmic determinants d. maternal factors, cell-to-cell signals e. Both b and d are correct.
d. maternal factors, cell-to-cell signals
MicroRNAs and small interfering RNAs both function similarly in "silencing" genes. What are two ways in which they may act? -degrade mRNA and bind to complementary mRNA sequences to prevent translation -cut up mRNAs using the Dicer enzyme and bind to complementary DNA sequences to prevent transcription -degrade mRNA and inhibit RNA splicing -cut up mRNAs using the Dicer enzyme and bind to complementary mRNA sequences to prevent translation -inhibit RNA splicing and bind to complementary DNA sequences to prevent transcription
degrade mRNA and bind to complementary mRNA sequences to prevent translation
The function of tRNA during protein synthesis is to __________. -transcribe mRNA -attach mRNA to the small subunit of the ribosome -guide ribosome subunits out of the nucleus through nuclear pores -deliver amino acids to their proper site -process mRNA
deliver amino acids to their proper site Each tRNA molecule is used repeatedly, picking up its designated amino acid in the cytosol, depositing this cargo at the ribosome, and leaving the ribosome to pick up another load.
At one point, as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred __________. -during translation -in a double-stranded DNA molecule -during transcription -when an mRNA codon paired with a tRNA anticodon -It is impossible to say, given this information.
during transcription
Which of the following is an important part of the developmental process in animals? a. apoptosis b. induction c. cell migration d. differentiation e. All of the above.
e. all of the above
In a eukaryote, activating transcription factors may stimulate gene expression by binding to a DNA site called a(n) __________. enhancer operon promoter histone silencer
enhancer
A point mutation in which a single base pair is inserted or deleted from DNA is called a(n) __________. frame-shift mutation missense mutation nonsense mutation inversion mutation translocation mutation right answer feedback:
frame-shift mutation
If you were to observe the activity of methylated DNA, you would expect it to -be very actively transcribed and translated. -be replicating nearly continuously. -induce protein synthesis by not allowing repressors to bind to it. -be unwinding in preparation for protein synthesis. -have turned off or slowed down the process of transcription.
have turned off or slowed down the process of transcription.
The expression of a gene located in a tightly coiled region of DNA can be promoted by __________. histone acetylation histone deacetylation the arrival of the RNA polymerase demethylation of DNA methylation of histone tails
histone acetylation
The bonds that hold tRNA molecules in the correct three-dimensional shape are __________ hydrophobic interactions hydrogen bonds ionic bonds peptide linkages covalent bonds
hydrophobic interactions
A nucleic acid probe is used to __________. clone genes make exact copies of DNA sequences identify genes that have been inserted into bacterial plasmids or separated by electrophoresis make DNA from RNA produce a large amount of DNA from a tiny amount of DNA
identify genes that have been inserted into bacterial plasmids or separated by electrophoresis
In a eukaryotic cell, transcription takes place __________ in the rough endoplasmic reticulum in the cytoplasm in the nucleus on the cell membrane on free ribosomes
in the nucleus
During the transcription of a given portion of a DNA molecule __________. -mRNA is synthesized on both chains of the DNA molecule, but first on one side and then the other -mRNA is synthesized on only one of the chains -mRNA is synthesized on both chains of the DNA molecule at once -half of the mRNA is synthesized on half of one chain; then the other -half of the mRNA is made on the other half of the DNA -All of the choices are correct.
mRNA is synthesized on only one of the chains
A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout an organism's chromosomes. This will probably cause __________ manufactured proteins to be short and defective the DNA to break up into thousands of short segments incorrect pairing between mRNA codons and amino acids no bad effects, as long as the stop codons are not also inserted into tRNA All of the choices are correct.
manufactured proteins to be short and defective
The first amino acid inserted into a new polypeptide chain in eukaryotic cells is usually __________. adenosine monophosphate alanine serine glycine methionine
methionine
What determines how long a particular mRNA molecule will persist in a eukaryotic cell? the length of the 5' cap the presence of proteasomes in the cytoplasm the number of introns removed during processing nucleotide sequences in the 3' untranslated region the number of exons removed during processing
nucleotide sequences in the 3' untranslated region
A base-pair substitution mutation in a germ cell line is likely to have NO effect on phenotype if the substitution __________ -prevents the initiation of transcription of the DNA sequence that codes for ATP synthase -changes a stop codon to a codon specifying an amino acid forms a new stop codon -occurs in an intron -changes the structure of an enzyme
occurs in an intron A base substitution in an intron that does not change the amino acid sequence of the polypeptide encoded by that gene would have no phenotypic effect on the organism.
Generally speaking, how many genetic codes are there? one three four 20 one for each organism
one Although slight variations do exist, the genetic code is universal. Nearly all organisms use the same genetic code to translate mRNA to protein.
During translation in a eukaryotic cell __________. -mRNA is synthesized by the bonding of free nucleotides to the bases on the template strand of DNA -polypeptides are synthesized at ribosomes, according to instructions carried by mRNA -ribosomes move out of the nucleus -ribosomes move into the nucleus -tRNA carries amino acid molecules to the nucleus, where they are added to a growing polypeptide chain
polypeptides are synthesized at ribosomes, according to instructions carried by mRNA
In many cases, more than one codon codes for the same amino acid. Because of this, we say that the code is __________ incomplete not specific redundant inaccurate vague
redundant
In general, operons that encode the enzymes of a biosynthetic (anabolic) pathway, such as the trp operon, are __________, and those encoding the enzymes of a catabolic pathway (such as the lac operon) are __________. inducible ... repressible easily mutated ... resistant to mutations permanently on ... permanently off repressible ... inducible permanently off ... permanently on
repressible ... inducible
What is the source of the reverse transcriptase used in recombinant DNA technology? cultured fungal cells plant cells retroviruses cultured phage-infected mammalian cells either retroviruses or cultured phage-infected mammalian cells
retroviruses
Which arrangement of the following four enzymes represents the order in which they would be used in a typical gene-cloning experiment resulting in the insertion of a cDNA into a bacterial plasmid? Begin with the gene's mRNA transcript. -reverse transcriptase, restriction enzyme, DNA polymerase, DNA ligase -reverse transcriptase, DNA ligase, DNA polymerase, restriction enzyme -reverse transcriptase, DNA polymerase, restriction enzyme, DNA ligase -restriction enzyme, reverse transcriptase, DNA polymerase, DNA ligase -restriction enzyme, DNA ligase, reverse transcriptase, DNA polymerase
reverse transcriptase, DNA polymerase, restriction enzyme, DNA ligase
In some cases DNA methylation and histone deacetylation combine to __________. form a transcription factor silence certain genes remove genomic imprinting form an enhancer turn certain genes on
silence certain genes Both DNA methylation and histone deacetylation tend to repress transcription.
Cells are able to distinguish proteins destined for secretion or for segregation to specific intracellular compartments from those that will remain in the cytoplasm because __________. -proteins destined for secretion or for a specific compartment are all synthesized in the nucleus, whereas cytoplasmic proteins are all synthesized in the cytoplasm -each compartment in the cell (the nucleus, lysosome, and so forth) has its own set of ribosomes that synthesize proteins unique to that compartment -there are two types of ribosomes: one group that synthesizes cytoplasmic proteins only, and another type that synthesizes secreted or compartment-specific proteins only -some proteins, as they begin to be synthesized, contain a signal region that causes the ribosome with its growing polypeptide to attach to the ER and translocate the polypeptide into the lumen (space) of the ER -ribosomes contain two types of subunits
some proteins, as they begin to be synthesized, contain a signal region that causes the ribosome with its growing polypeptide to attach to the ER and translocate the polypeptide into the lumen (space) of the ER
In an inducible operon, the inducer is often the __________ in the pathway being regulated; the inducer binds to the __________, thus rendering it __________. substrate ... repressor ... inactive end product ... corepressor ... inactive substrate ... corepressor ... inactive end product ... repressor ... inactive substrate ... repressor ... active
substrate ... repressor ... inactive
Bacteria can transcribe and translate human genes to produce functional human proteins because __________ -RNA has catalytic properties -eukaryotes do not really need a nucleus -the genetic code is nearly universal -bacterial ribosomes and eukaryotic ribosomes are identical -bacterial and eukaryotic RNA polymerases are identical
the genetic code is nearly universal
During translation, amino acid chain elongation occurs until __________. the ribosome encounters a "stop" codon the polypeptide is long enough all tRNAs are empty no further amino acids are needed by the cell the ribosome runs off the end of the mRNA strand
the ribosome encounters a "stop" codon
When genes are expressed, they produce __________. enzymes RNA molecules phenotypic traits polypeptides the second and fourth choices are correct
the second and fourth choices are correct (RNA molecules and polypeptides)
Which of the following is a function of a signal peptide? -to signal the initiation of transcription -to terminate translation of the messenger RNA -to bind RNA polymerase to DNA and initiate transcription -to translocate polypeptides across the ER membrane -to direct an mRNA molecule into the cisternal space of the ER
to translocate polypeptides across the ER membrane
Because eukaryotic genes contain introns, they cannot be translated by bacteria, which lack RNA-splicing machinery. But if you want to engineer a bacterium to produce a eukaryotic protein, you can synthesize a gene without introns. A good way to do this is to __________. work backward from mRNA to make a version of the gene without introns use a phage to insert the desired gene into a bacterium alter the bacteria so that they can splice RNA use a nucleic acid probe to find a gene without introns use a restriction enzyme to remove introns from the gene
work backward from mRNA to make a version of the gene without introns