Bio Test
An Okazaki fragment has which of the following arrangements?
5' RNA nucleotides, DNA nucleotides 3'
The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer.You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible?
8
Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
8%
In an analysis of the nucleotide composition of DNA, which of the following will be found?
A + C = G + T
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A gene from an organism can theoretically be expressed by any other organism.
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate?
Any mutation in the sequence is selected against.
A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?
B
Use the accompanying diagram of the key developmental events in the life cycle of the fruit fly Drosophila to select the statement that best describes the timing and coordination of events necessary for normal fruit fly development.
Cytoplasmic determinants localized in the unfertilized egg provide positional information for placement of the anterior-posterior axis in the embryo.
In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure above would be expected after one round of DNA replication in the presence of 14N?
D
Which of the following provides some evidence that RNA probably evolved before DNA?
DNA polymerase uses primer, usually made of RNA.
After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?
Descendants of the living cells are also phosphorescent.
Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya?
Domain Archaea have numerous transcription factors.
Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following?
Eukaryotic exons may be spliced in alternative patterns.
What is the function of GTP in translation?
GTP energizes the formation of the initiation complex, using initiation factors.
Which of the following statements describes chromatin?
Heterochromatin is highly condensed, whereas euchromatin is less compact. Submit
Which of the following statements is true of histones?
Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
Use the following list of choices for the following question:I. helicaseII. DNA polymerase IIIIII. ligaseIV. DNA polymerase IV. primaseWhich of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?
IV
The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?
If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'Which of the following is a useful feature of introns for this model?
Introns allow exon shuffling.
What is the function of the release factor (RF)?
It binds to the stop codon in the A site in place of a tRNA.
How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?
It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication.
Which of the following is characteristic of the product of the p53 gene?
It is an activator for other genes.
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.
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
It joins Okazaki fragments together.
Why might a point mutation in DNA make a difference in the level of a protein's activity?
It might substitute a different amino acid in the active site.
Which of the following describes the function of an enzyme known as Dicer?
It trims small double-stranded RNAs into molecules that can block translation.
Garrod's information about the enzyme alteration resulting in alkaptonuria led to further elucidation of the same pathway in humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe) to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria?
It would have no effect, because tyrosine is also available from the diet.
If a newly made polypeptide is to be secreted from a cell, what must occur before it is secreted?
Its signal sequence must target it to the ER, after which it goes to the Golgi.
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might result?
Removal of the 5' UTR also removes the 5' cap and the mRNA will quickly degrade.
The tRNA shown in the figure has its 3' end projecting beyond its 5' end. What will occur at this 3' end?
The amino acid binds covalently.
If a cell were unable to produce histone proteins, which of the following would be a likely effect?
The cell's DNA couldn't be packed into its nucleus.
In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?
The entire template molecule is represented in the product.
The template strand of a gene contains this sequence: 3'-TAC TAG GCT AGT TGA-5'. A mutation occurs that changes the gene sequence to 3'-TAC TAG ACT AGT TGA-5'. How does this mutation affect the resulting amino acid sequence?
The mutation introduces a stop codon.
A researcher introduces double-stranded RNA into a culture of mammalian cells, and can identify its location or that of its smaller subsections experimentally, using a fluorescent probe.In addition, she finds what other evidence of this single-stranded RNA piece's activity?
The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply?
There are also genes for RNAs other than mRNA.
Which of the following statements is true about protein synthesis in prokaryotes?
Translation can begin while transcription is still in progress.
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
UUU.
In the 1920s, Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals-she used nitrogen mustards-have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation?
We want to prevent any increase in mutation frequency.
Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?
a base deletion near the start of a gene
Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
a base-pair deletion
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
a polypeptide missing an amino acid.
If a Drosophila female has a homozygous mutation for a maternal effect gene,
all of her offspring will show the mutant phenotype, regardless of their genotype.
What is a ribozyme?
an RNA with enzymatic activity
The role of a metabolite that controls a repressible operon is to
bind to the repressor protein and activate it.
Alternative RNA splicing
can allow the production of proteins of different sizes and functions from a single mRNA.
A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer?
colorectal only
A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in
continuous transcription of the structural gene controlled by that regulator.
A lack of which molecule would result in the cell's inability to "turn off" genes?
corepressor
A frameshift mutation could result from
either an insertion or a deletion of a base.
To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
endonuclease, DNA polymerase I, DNA ligase
What type of bonding is responsible for maintaining the shape of the tRNA molecule?
hydrogen bonding between base pairs
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see?
inactivation of the selected genes
When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?
methylation and phosphorylation of histone tails
Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?
newly formed polypeptide
At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for most of the rest?
non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
Which of the following represents the order of increasingly higher levels of organization of chromatin?
nucleosome, 30-nm chromatin fiber, looped domain
Which of the enzymes synthesizes short segments of RNA?
primase
A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form.
proline-threonine.
Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell?
removal of the 5' cap
The product of the bicoid gene in Drosophila provides essential information about
the anterior-posterior axis.
The lactose operon is likely to be transcribed when
the cyclic AMP and lactose levels are both high within the cell.
Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?
the diameter of the helix
The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that
the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose. Submit
BRCA1 and BRCA2 are considered to be tumor-suppressor genes because
their normal products participate in repair of DNA damage.
What is the function of DNA polymerase III?
to add nucleotides to the 3' end of a growing DNA strand
When the spliceosome binds to elements of this structure, where can it attach?
to the end of an intron
Which of the following is a function of a signal peptide?
to translocate polypeptides across the ER membrane
The tryptophan operon is a repressible operon that is
turned off whenever tryptophan is added to the growth medium.
The following question refers to this figure of a simple metabolic pathway: According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
2
The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer.You add polynucleotide phosphorylase to a solution of ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be possible?
27
A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be
3' AAA-GAA-TAA-CAA 5'.
The anticodon loop of the first tRNA that will complement this mRNA is
3' GGC 5'
A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide?
3' TTT-CCC-AAA-GGG-TTT-CCC
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is
3' UCA 5'.
RNA polymerase moves in which direction along the DNA?
3' to 5' along the template strand
DNA template strand 5' ____________________________ 3'DNA complementary strand 3' ____________________________ 5'Given the locally unwound double strand above, in which direction does the RNA polymerase move?
3' → 5' along the template strand
At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork:3' C C T A G G C T G C A A T C C 5'An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?
5' A C G U U A G G 3' Submit
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'Which components of the previous molecule will also be found in mRNA in the cytosol?
5' UTR E1 E2 E3 E4 UTR 3'
Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression?
A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.
Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?
A specific combination of control elements in each gene's enhancer coordinates the simultaneous activation of the genes.
The nitrogenous base adenine is found in all members of which group?
ATP, RNA, and DNA
Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?
Allolactose binds to the repressor protein.
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?
Anterior structures would form in both sides of the embryo.
Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely?
Beta galactosidase will not be produced.
Since Watson and Crick described DNA in 1953, which of the following might best explain why the function of small RNAs is still being explained?
Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible.
In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
DNA contains phosphorus, whereas protein does not.
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
Two potential devices that eukaryotic cells use to regulate transcription are
DNA methylation and histone modification.
Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
DNA polymerase III
A new DNA strand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end.
The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that will be joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?
DNA polymerase is a directional enzyme that synthesizes leading and lagging strands during replication.
A researcher introduces double-stranded RNA into a culture of mammalian cells, and can identify its location or that of its smaller subsections experimentally, using a fluorescent probe.Within the first quarter hour, the researcher sees that the intact RNA is found in the cells. After 3 hours, she is not surprised to find that
Dicer enzyme has reduced it to smaller double-stranded pieces.
Where does tRNA #2 move to after this bonding of lysine to the polypeptide?
E site
Which of the following investigators was/were responsible for the following discovery?In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
Erwin Chargaff
Why do histones bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged.
Use the following list of choices for the following question:I. helicaseII. DNA polymerase IIIIII. ligaseIV. DNA polymerase IV. primaseWhich of the enzymes separates the DNA strands during replication?
I
Use the following list of choices for the following question:I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes covalently connects segments of DNA?
III
There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?
It cannot bind to the inducer.
Which of the following is a function of a poly-A signal sequence?
It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10-35 nucleotides away.
Which of the following statements describes the eukaryotic chromosome?
It consists of a single linear molecule of double-stranded DNA plus proteins.
What is the effect of a nonsense mutation in a gene?
It introduces a premature stop codon into the mRNA.
RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such variability in RNA polymerase?
It might allow the polymerase to recognize different promoters under certain environmental conditions.
In his transformation experiments, what did Griffith observe?
Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?
No replication fork will be formed.
Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying leucine, Leu). What will be the effect on translation in this cell?
One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.
Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
During splicing, which molecular component of the spliceosome catalyzes the excision reaction?
RNA
The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called
RNA interference.
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?
RNA polymerase II
For a repressible operon to be transcribed, which of the following must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
Which of the following statements best describes the termination of transcription in prokaryotes?
RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?
Replication is not conservative.
In E. coli replication the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following would you expect?
Replication would not occur on either the leading or lagging strand. Submit
What is meant by the description "antiparallel" regarding the strands that make up DNA?
The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. Submit
An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result?
The amino acid methionine will not bind.
Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the repressor gene (lac I), along with its promoter, to a position at some several thousand base pairs away from its normal position, which will you expect to occur?
The lac operon will function normally.
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find?
The molecule is digested by exonucleases since it is no longer protected at the 5' end.
Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the operator to the far end of the operon, past the transacetylase (lacA) gene, which of the following would likely occur when the cell is exposed to lactose?
The structural genes will be transcribed continuously.
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all.Which of the following is a likely explanation for the lack of transgene expression in the fifth cell line?
The transgene integrated into a heterochromatic region of the genome.
Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules and 2 H2B molecules, and the other as 2 H3 and 2 H4 molecules. Which of the following is supported by this data?
The two types of tetramers associate to form an octamer.
In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine). After several minutes, the DNA is switched to nonradioactive medium and is then viewed by electron microscopy and autoradiography. The figure above represents the results. It shows a replication bubble, and the dots represent radioactive material. Which of the following is the most likely interpretation of the results?
There are two replication forks going in opposite directions.
Which of the following is true of transcription in domain Archaea?
There is only one kind of RNA polymerase.
Which of the following statements describes proto-oncogenes?
They can code for proteins associated with cell growth.
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?
They cannot repair thymine dimers.
The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?
UUC
Hershey and Chase used a DNA-based virus for their work. What would the results have been if they had used an RNA virus?
With an RNA virus radioactive RNA would have been in the final pellet.
You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. Which of the following might best give you an answer?
You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.
Of the following, which is the most current description of a gene?
a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene?
a bacterial promoter sequence
Which of the following is most likely to have a small protein called ubiquitin attached to it?
a cyclin that usually acts in G1, now that the cell is in G2
Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
a deletion of two nucleotides
Which of the following would you expect of a eukaryote lacking telomerase?
a reduction in chromosome length in gametes
Which of the following best describes siRNA?
a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by
a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.
Which of the following mutations is most likely to cause a phenotypic change?
a single nucleotide deletion in an exon coding for an active site
Which of the following nucleotide triplets best represents a codon?
a triplet in the same reading frame as an upstream AUG
Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways?
allowing the organism to adjust to changes in environmental conditions
In response to chemical signals, prokaryotes can do which of the following?
alter the level of production of various enzymes
A simple metabolic pathway is shown below. A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
an accumulation of A and no production of B and C
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?
an assembled ribosome with a polypeptide attached to the tRNA in the P site
How do we describe transformation in bacteria?
assimilation of external DNA into a cell
When the spliceosome binds to this transcript, where can it attach?
at certain sites along an intron
DNA template strand 5' ____________________________ 3'DNA complementary strand 3' ____________________________ 5'If the DNA shown corresponds to a transcription unit, where would the promoter be located?
at/near the right end
In eukaryotes, general transcription factors
bind to other proteins or to a sequence element within the promoter called the TATA box.
Steroid hormones produce their effects in cells by
binding to intracellular receptors and promoting transcription of specific genes.
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.
Tumor-suppressor genes
can encode proteins that promote DNA repair or cell-cell adhesion.
In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP?
decrease in glucose and increase in cAMP
In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see?
decreased chromatin condensation
researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see?
decreased chromatin condensation
The fact that plants can be cloned from somatic cells demonstrates that
differentiated cells retain all the genes of the zygote.
Which of the following sets of materials are required by both eukaryotes and prokaryotes for replication?
double-stranded DNA, four kinds of dNTPs, primers, origins of replication
Genomic imprinting, DNA methylation, and histone acetylation are all examples of
epigenetic phenomena.
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?
gaps left at the 5' end of the lagging strand
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because
genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
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?
genes involved in control of the cell cycle
Forms of the Ras protein found in tumors usually cause which of the following?
growth factor signaling to be hyperactive
If you were to observe the activity of methylated DNA, you would expect it to
have turned off or slowed down the process of transcription.
Mutations in which of the following genes lead to transformations in the identity of entire body parts?
homeotic genes
5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'Suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5' end of intron 1 (I1). What might occur?
inclusion of I1 in the mRNA
Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?
inducer
Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator?
inducer
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
leading strands and Okazaki fragments.
A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that
many noncoding stretches of nucleotides are present in eukaryotic DNA.
What amino acid sequence will be generated, based on the following mRNA codon sequence?5' AUG-UCU-UCG-UUA-UCC-UUG 3'
met-ser-ser-leu-ser-leu
During DNA replication,
methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylates daughter strands after replication.
If A, B, and C are all required for growth, a strain mutant for the gene-encoding enzyme B would be capable of growing on which of the following media?
minimal medium supplemented with C only
If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on which of the following media?
minimal medium supplemented with nutrient B only
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all.Of the lines that express the transgene, one is transcribed but not translated. Which of the following is a likely explanation?
no AUG in any frame
Transcription factors in eukaryotes usually have DNA binding domains as well as other domains that are also specific for binding. In general, which of the following would you expect many of them to be able to bind?
other transcription factors
Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?
pattern formation
Embryonic lethal mutations result in
phenotypes that are never born/hatched.
Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons. These are known as
piRNA
The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following?
polypeptide factors plus GTP
A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
The cancer-causing forms of the Ras protein are involved in which of the following processes?
relaying a signal from a growth factor receptor
What is the function of topoisomerase?
relieving strain in the DNA ahead of the replication fork
Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?
replication without separation
Which of the following is a protein produced by a regulatory gene?
repressor
Which of the following genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo?
segmentation genes
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
sequence of bases
Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
several transcription factors
Which of the following help(s) to hold the DNA strands apart while they are being replicated?
single-strand binding proteins Submit
Transcription of the structural genes in an inducible operon
starts when the pathway's substrate is present.
One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs?
targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease
The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?
that the critical function of telomeres must be maintained
In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?
the 30-nm chromatin fiber
Given the damage caused by UV radiation, the kind of gene affected in those with XP is one whose product is involved with
the ability to excise single-strand damage and replace it.
The leading and the lagging strands differ in that
the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
What is considered to be the first evidence of differentiation in the cells of an embryo?
the occurrence of mRNAs for the production of tissue-specific proteins
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that
the rules for base pairing between the third base of a codon and tRNA are flexible.
Which of the following is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA