Module 4 Exam
Two modular elements that appear as consensus sequences upstream from RNA polymerase II transcription start sites are TTAA and CCTT. microsatellites and transposons. rDNA and nucleolar organizers. enhancers and telomeres. TATA and CAAT.
TATA and CAAT.
The following table lists several genotypes associated with the lacoperon in E. coli. For each, indicate with a "+" or a "—" whether β-galactosidase would be expected to be produced at induced levels. (Assume that glucose is not present in the medium.)
(a) -, + (b) +,+ (c) +,+ (d) +,+
Three major types of RNAs were discussed in some detail: mRNA, rRNA, and tRNA. For each of the conditions below predict the consequences in terms of the population of proteins being synthesized in a particular cell. What qualitative and quantitative changes, if any, are expected in the individual protein involved (if one is involved) and in the population of proteins produced in that cell? (a) An acridine dye-induced mutation in mRNA. The condition is heterozygous in the involved cell. (b) A deletion (homozygous) that removes approximately half of the rRNA genes.
(a) Population of proteins: Half of the protein products of that gene will be defective, and the other half will be normal. Individual protein: The protein should show multiple amino acid substitutions "downstream" from the point of the mutation. If a nonsense triplet is introduced, the protein would be shortened in the substituted region. (b) Population of proteins: There would be an overall reduction in protein synthesis. Individual protein: All of the proteins would be made in their normal form, but at reduced levels.
(a) Describe the structural components of the lactose operon in E coli. (b) State the function of the lac regulator gene. (c) State the function of β-galactosidase in the lac system. Separate and clearly label your answer parts A-C in the box below.
(a) operator-physical component of DNA where repressor binds, repressor-trans-acting protein that binds operator when lactose is absent, lacZ-Bgal structural gene, lacY-Bgal permease, lacA-Bgal transacetylase (b) The regulator gene produces a repressor protein, which interacts with the operator to shut off transcription. In the presence of lactose, the repressor protein does not interact with the operator. (c) β-galactosidase cleaves the lactose sugar into its components glucose and galactose.
Under the system of genetic control of the tryptophan operon, when there are high levels of tryptophan in the medium, transcription of the trp operon occurs at high levels. when there are high levels of tryptophan in the medium, ribosomes "stall" and reduce the levels of tryptophan synthesized. when there are high levels of tryptophan in the medium, transcription of CAP (CRP) occurs at high levels. no transcription occurs under any nutritional circumstance because negative controls inhibit transcription. when there is no tryptophan in the medium, transcription of the trpoperon occurs at high levels.
when there is no tryptophan in the medium, transcription of the trpoperon occurs at high levels.
Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at "normal" rates. Such individuals are likely to suffer from Huntington disease. SCID. xeroderma pigmentosum. muscular dystrophy. phenylketonuria.
xeroderma pigmentosum.
What are three ways in which gene regulation is accomplished by modifying the structure of chromatin?
1 Modification of Histone proteins. 2. Chromatin remodeling 3. DNA methylation
Fill in the blanks in the "level of transcription" column of this table with: + for high levels of transcription, and - for minimal levels of transcription of the lac operon. Consider regulation by both the lac repressor and CAP (catabolite activator protein). The strain is wild type, with no partial diploidy. Please label your answer with numbers 1-4 based on the chart below. Medium conditions Level of transcription 1high glucose, no lactose 2no glucose, high lactose 3high glucose, high lactose 4no glucose, no lactose
1. - 2. + 3. - 4. -
Over the past decade, the most significant finding in biology has been the identification of miRNAs and siRNAs and their role in regulating the development of many multicellular organisms. Briefly describe the four different ways these small RNAs influence gene expression.
1. Cleavage of mRNA 2. Inhibition of translation 3. Transcriptional silencing 4. Degradation of mRNA
Name six different levels at which gene expression might be controlled.
1. alteration or modification of the gene structure at the DNA level 2. transcriptional regulation 3. regulation at the level of mRNA processing 4. regulation mRNA stability 5. regulation of translation 6. regulation by post-translational modification of the synthesized protein
Describe 3 pieces of evidence that supports the hypothesis that DNA methylation is important factor in gene regulation.
1. an inverse relationship exists between the degree of methylation and the degree of gene expression 2. methylation patterns are tissue specific and heritable for all cells in that tissue 3. incorporation of 5-azacytyine ( which is not able to be methylated) causes changes in the pattern of gene expression
Fill in the blanks in the "strain genotype" column of the following table. Write chromosomal genotypes with no partial diploidy. (+) means transcription of the lac operon. (-) means no transcription of the operon. The first line is filled in for reference. Please label your answers 1-3. Include the strain genotype for lacI, lacP, lacO, lacZ, and lacY
1. lacI+ lacP+ lacO+ lacZ+ lacY+ 2. lacI+ lacP+ lacOc lacZ+ lacY+ OR lacI- lacP+ lacO+ lacZ+lacY+ 3. lacI+ lacP- lacO+ lacZ+ lacY+OR lacIs lacP- lacO+ lacZ+ lacY+ OR lacIs lacP+ lacO+ lacZ+lacY+
Describe some important differences between bacterial and eukaryotic cells that affect the way in which genes are regulated.
1.Bacterial genes are often clustered in operons and are coordinately expressed through the synthesis of a single polygenic mRNA. Eukaryotic genes are typically separate, with each containing its own promoter and transcribed on individual mRNAs. Coordinate expression of multiple genes is accomplished through the presence of response elements. Genes sharing the same response element will be regulated by the same regulatory factors. 2. In eukaryotic cells, chromatin structure plays a role in gene regulation. Chromatin that is condensed inhibits transcription. So, for expression to occur, the chromatin must be altered to allow for changes in structure. Acetylation of histone proteins and DNA methylation are important in these changes. 3. At the level of transcription initiation, the process is more complex in eukaryotic cells. In eukaryotes, initiation requires a complex machine involving RNA polymerase, general transcription factors, and transcriptional activators. Bacterial RNA polymerase is either blocked or stimulated by the actions of regulatory proteins. 4. Finally, in eukaryotes the action of activator proteins binding to enhancers may take place at a great distance from the promoter and structural gene. These distant enhancers occur much less frequently in bacterial cells.
Explain two different ways that intragenic suppressors may reverse the effects of mutations
1.Intragenic suppression is the result of second mutations within a gene that restore a wild-type phenotype. The suppressor mutations are located at different sites within the gene from the original mutation. One type of suppressor mutation restores the original phenotype by reverting the meaning of a previously mutated codon to that of the original codon. The suppressor mutation occurs at a different position than the first mutation, which is still present within the codon. Intragenic suppression may also occur at two different locations within the same protein. If two regions of a protein interact, a mutation in one of these regions could disrupt that interaction. The suppressor mutation in the other region would restore the interaction. Finally, a frameshift mutation due to an insertion or deletion could be suppressed by a second insertion or deletion that restores the proper reading frame.
What role does RNA stability play in gene regulation? List three types of RNA structural elements that can affect the stability of an RNA molecule in eukaryotic cells. Explain how these elements act to influence RNA stability.
1.The total amount of protein synthesized is dependent on how much mRNA is available for translation. The amount of mRNA present is dependent on the rates of mRNA synthesis and degradation. Less-stable mRNAs will be degraded and become unavailable as templates for translation. The presence of the 5' cap, 3' poly(A) tail, the 5' UTR, 3' UTR, and the coding region in the mRNA molecule affects stability.Poly(A) binding proteins (PABP) bind at the 3' poly(A) tail. These proteins contribute to the stability of the tail, and protect the 5' cap through direct interaction. Once a critical number of adenine nucleotides have been removed from the tail, the protection is lost and the 5' cap is removed. The removal of the 5' cap allows for 5' to 3' nucleases to degrade the mRNA.
In general, mutation rates in humans occur in the range of ________ (frequency) per gamete per generation.
10^-5 to 10^-6
Determine a possible metabolic pathway that would give the results seen for the four mutant strains, A through D. (If necessary, use a separate piece of paper to diagram the pathway). Then, fill-in the blanks below with Strain A-D or Supplement 1-4, using this generic metabolic pathway as a guide:
4,2,1,3 C,B,A,D
In what way can 5'-azacytosine influence transcription?
5-azacytosine causes undermethylation of sites of incorporation and changes in the pattern of gene expression
Name two mutagens that would be classified as base analogs. acridine orange and proflavin ultraviolet light and cosmic radiation hydroxyurea and peroxidase ethylmethane sulfonate and ethylmethylketone peroxide 5-bromouracil and 2-aminopurine
5-bromouracil and 2-aminopurine
It is estimated that transposable elements compose approximately what percent of the human genome? <1 99 10 1 50
50
What is a mutation? A change in the DNA sequence A change of amino acid A change in the phenotype A change in allele frequency
A change in the DNA sequence
Complementation analysis can be used to determine whether two mutations are in the same gene. Explain how to test for complementation and how one would interpret the results.
A cross is made between the two homozygous strains. If the F1 progeny are wild type, complementation has occurred and the two mutations must lie in two separate genes.
It has been found that a particular "+ —" combination of frameshift mutations in gene X gives a wild-type phenotype, whereas a "— +" combination gives a mutant phenotype, even though the sites of insertion/deletion are the same. How might these results be explained?
A frameshift in the "+ -" direction may have introduced a nonsense triplet, which was not introduced, by chance, by the opposite "- +" combination
What is a homeobox, and what is its significance?
A homeobox is a DNA sequence, around 180 base pairs long, found within genes that are involved in the regulation of patterns of anatomical development (morphogenesis) in animals, fungi and plants.
The _________ can be used to quickly screen chemicals for their ability to be mutagenic (and hence potentially carcinogenic).
AMES
How can the expression of a gene be drastiacally altered by the presence of comparatively small numbers of RNA molecules? What is the term for this class of gene regulation?
As a research tool, short synthetic dbl. stranded RNAi molecules are introduced into cells where they trigger RNA degradation pathways, which target mRNAs. This is used to knock out the function of a gene. term is RNAi
Assume that you wished to generate conditional mutations (such as temperature sensitive mutations) for the study of cell-cycle genes in yeast. Of the mutagens listed in the following, which would be the most likely to generate such mutations? radiation nitrosoguanidine ethyl methane sulfonate (EMS) B and C transposon insertion
B and C
This structure forms when an extra X chromosome is methylated and largely inactivated. It is most commonly found in females.
Barr body
Why do insertions and deletions often have more drastic phenotypic effects than base substitutions do?
Because amino acid codons consist of three nucleotides, insertions and deletions that involve any multiple of three nucleotides will leave the reading frame intact. However, the addition or removal of one or more amino acids may still affect the phenotype. Insertions or deletions that do not alter the translation reading frame are called "in-frame" insertions and deletions.
What is meant by the term reverse genetics?
Begins with a gene of unknown function, first inducing mutations and then checking the effect of the mutation on the phenotype
Regulatory proteins that bind DNA have common motifs that interact with sequences of DNA. How do amino acids in DNA-binding proteins interact with DNA? a) and c) By forming hydrogen bonds with DNA bases None of the above. By forming covalent bonds with DNA sugars By forming covalent bonds with DNA base
By forming hydrogen bonds with DNA bases
Name three types of consensus sequences or modular DNA sequences that exist upstream from the coding regions of some eukaryotic genes.
CAAT, TATA, GC sequence
Enhancers are said to be cis-acting. What is meant by cis-acting, and what are enhancers?
Cis-acting means they can act only on genes found on the same chromosome as them. Enhancers are DNA sequences that increase transcription other other DNA sequences
The region of a protein that is capable of holding on to a particular nucleotide sequence in order to affect proper gene regulation.
DNA binding domain
Which term most appropriately refers to a regulatory protein in prokaryotes? helicase activation RNA processing translation gyrase action DNA binding protein
DNA binding protein
Strand discrimination during the process of _____________ is based on DNA methylation in E. coli.
DNA repair
Describe the general structure of a transcription factor. What two domains do transcription factors tend to have?
DNA-binding domain and an activation domain
When regions around genes become sensitive to the enzyme ______________ this is an indication that those regions are becoming ______________ active.
DNase I, transcriptionally
Experiments involving nuclear transplantation in amphibians indicate that nuclei derived from blastula are more likely to support development of complete and normal adults compared with those derived from later stages of development. What do these experiments tell us about the process of development?
Development occurs as a series of cascades, with early genes influencing late genes, at times with stability. Such progressive determination, if stable, may be irreversible and fail to support development of an entire organism from a single cell. A number of epigenetic factors such as chromatin remodeling and DNA methylation are also likely to come into play.
List at least two different types of DNA repair and briefly explain how each is carried out.
Direct Repair: the single nucleotide which is changed or mutated is corrected to the original nucleotide Nucleotide-excision Repair: a bulky region of DNA that changes the double-helix structure (pyrimidine dimer) is excised/removed from the sequence to restore its original structure and sequence
Recent discoveries on causes of fragile-X syndrome, myotonic dystrophy, and Huntington disease indicate what type of genetic alteration?
Expansion of trinucleotide repeats
Design an experiment that would allow you to determine if a particular nucleus in a Drosophila embryo is capable of directing development of an entire new fly.
Experiments in support of such genomic equivalence include the following: the observation that chromosome number and structure do not consistently change in different cells of an organism, nuclear transplantation in amphibians, and the presence of genes but no gene products in some tissues (hemoglobin, for example). The recent cloning of Dolly also supports the above. For the Drosophila experiment, one could do nuclear transplantation similar to the classic experiments in amphibians and recent experiments in mammals or transplant a cell from embryos of one genotype to the posterior end of the early embryos of another genotype. The transplanted cells would be reprogrammed into germ cells by the posterior P granules. The transplant can be detected in the next generation by the recognizable different phenotypes due to different genotypes of the donor and recipient.
Under certain circumstances, one can make use of expression libraries to identify and clone a gene of interest. Describe an expression library and how one could be used to clone a gene.
Expression libraries contain cDNA clones inserted into vectors that have a promoter that will drive the expression of the cDNA within E. coli host cells. Antibodies specific for a purified protein will recognize the protein produced in bacteria from the cDNA vector. This allows the investigator an opportunity to select the relevant clone from the library.
Describe what is meant by the term forward genetics.
Forward genetics involves the isolation of mutants that show differences in a particular phenotype of interest. Mutant isolation is usually followed by an analysis of gene pathways through epistasis and/or complementation analyses. Then the gene is usually mapped and cloned and studied by a variety of molecular and developmental approaches.
Alternative RNA splicing is a method that apparently evolved for the production of many different polypeptides from the same pre-mRNA. Provide an example of alternative splicing.
Fourteen exons occur in the alpha-tropomyosin gene, six of which make up three pairs that are alternatively spliced. Ten different forms of alpha-tropomyosin are expressed in a tissue-specific manner., The drosophila protein Dscam has many (~38000) sites that could be alternatively spliced. In theory this leads to more polypeptide products than there are genes in the Drosophila genome, Genetic mutations in the human SMN2 gene can lead to alternatively spliced protein products that can cause spinal muscle atrophy
What is functional complementation?
Functional complementation is a process whereby plasmids or other vectors containing all, or at least a high percentage, of the genes from an organism are individually transformed into a mutant strain until one clone restores the mutant phenotype to wild type. This process usually allows the investigators an opportunity to isolate a functional stretch of DNA about which some knowledge of function is already available.
__________ mutations produce new traits and are usually dominant. Group of answer choices Induced Forward Lethal Spontaneous Gain-of-function
Gain-of-function
What is the common influence of ultraviolet light on DNA? Note that simply stating "mutation" or "increase in mutation rate" is not an acceptable answer
Generation of pyrimidine dimers
What is the role of maternal-effect genes?
Genes derived from the maternal genome are actively transcribed to support the zygote and are required for the proper patterning of the embryo. Mutant phenotypes of maternal-effect reflect the genotype of the mother.
The catabolite repression system in E. coli essentially represses the lacoperon when glucose is present. What evolutionary advantage would favor the evolution of such a system?
Glucose can enter glycolysis "as is," while lactose must first be split into glucose and galactose. To do so, the energy requiring synthesis of β-galactosidase is needed. It is energy-efficient to burn glucose rather than lactose.
How was it determined that X rays are mutagenic?
H. J. Muller determined that a direct relationship occurred between X-linked recessive lethals and X ray dose in Drosophila.
Describe the structure of a helix-turn-helix (HTH) motif. What is the general function of such motifs?
HTH domains were the first DNA-binding motifs to be identified. They are found in the cro, lac, and Trp repressors. A geometric conformation is formed by two adjacent α helices separated by a "turn" of several amino acids. Such motifs bind to the major grooves of DNA and interact with the DNA backbone. Many HTH-containing proteins regulate gene expression.
What are homeotic genes and what do they do?
Homeotic genes play crucial roles in developmental processes in higher organisms by coding for regulatory proteins (e.g., transcription factors) that activate other genes that control segment-specific characteristics of body parts. Homeotic genes control the fate and ultimate development of body segments. Mutations in homeotic genes cause body parts to appear in the wrong segments of the body.
Assume that a new mutation occurs in the germ line of an individual. What finding would suggest that the new mutation is dominant rather than recessive?
If dominant and if passed to the next generation, it would be expressed. New recessive mutations are not normally expressed in the next generation unless, through a combination with a like mutation from the other parent, they are homozygous.
Certain mutations in the regulator gene of the lac system in E. coli result in maximal synthesis of the lac proteins (β-galactosidase, etc.) even in the absence of the inducer (lactose). Provide an explanation for this observation.
If there is a mutation in either the repressor gene or the operator binding site, translation will continue. A mutation in the repressor gene will either make a non-functional repressor protein or not make one at all. A mutation in the operator binding site will not allow the repressor protein to bind. Both of these situations mean the polymerase can bind even in the absence of lactose.
When generating a series of mutations in an organism, how does a genetic screen differ from a mutation selection?
In a genetic screen, one mutagenizes the organism and then physically searches for the mutations. In a selection experiment, conditions are established in which only the relevant organisms survive. Selection is usually accomplished by killing or inhibiting the growth of irrelevant organisms.
Riboswitches were first discovered in 2002 and have been found in... plants bacteria In all of the listed organisms fungi archaea
In all of the listed organisms
What is catabolite repression? How does it allow a bacterial cell to use glucose in preference to other sugars?
In catabolite repression, the presence of glucose inhibits or represses the transcription of genes involved in the metabolism of other sugars. Because the gene expression necessary for utilizing other sugars is turned off, only enzymes involved in the metabolism of glucose will be synthesized. Operons that exhibit catabolite repression are under the positive control of catabolic activator protein (CAP). For CAP to be active, it must form a complex with cAMP. Glucose affects the level of cAMP. The levels of glucose and cAMP are inversely proportional—as glucose levels increase, the level of cAMP decreases. Thus, CAP is not activated.
Which of the following is NOT true regarding the differences in mRNA between prokaryotic cells and eukaryotic cells? In eukaryotic cells, mRNA is spliced before translation, while in prokaryotic cells there is no mRNA splicing. In eukaryotic cells, the 3' end of mRNA is modified with a tail, while in porkaryotic cells there is no tail. In eukaryotic cells, the 5' end of mRNA is modified with a cap, while in prokaryotic cells there is no cap. In eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not coupled.
In eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not coupled.
Which of the following is NOT true regarding the differences in mRNA between prokaryotic cells and eukaryotic cells? In eukaryotic cells, the 3' end of mRNA is modified with a tail, while in porkaryotic cells there is no tail. In eukaryotic cells, mRNA is spliced before translation, while in prokaryotic cells there is no mRNA splicing. In eukaryotic cells, the 5' end of mRNA is modified with a cap, while in prokaryotic cells there is no cap. In eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not coupled.
In eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not coupled.
Which of the following is NOT true regarding the differences in mRNA between prokaryotic cells and eukaryotic cells? In eukaryotic cells, the 5' end of mRNA is modified with a cap, while in prokaryotic cells there is no cap. In eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not coupled. In eukaryotic cells, mRNA is spliced before translation, while in prokaryotic cells there is no mRNA splicing. In eukaryotic cells, the 3' end of mRNA is modified with a tail, while in porkaryotic cells there is no tail.
In eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not coupled.
Molecular/structural orientations (gradients) in an egg are thought to play a significant role in development. What is the origin of such gradients? What evidence indicates that the maternal genotype is involved in providing such gradients?
In examples of maternal effects, the mother's genotype establishes the early body plan. During formation of any egg, nutritional, regulatory, and informational molecules (RNAs) are placed in appropriate positions for development of the embryo. In Drosophilamany maternal-effect genes have been identified.
Present a detailed description of the actions of the regulatory proteins in a) inducible and b) repressible enzyme systems.
Inducible system: The repressor is normally active, but the inducer inactivates the repressor. Repressible system: The repressor is normally inactive but is activated by the corepressor. Active repressors turn off transcription.
Describe how acridine dyes cause frameshift mutations.
Intercalation b/t bases of intact DNA causes DNA polymerase to add or skip a base during replication
What is the function of cAMP in regulation of the lac operon? It inactivates an activator protein. It activates an activator protein. It activates a repressor protein. It inactivates a repressor protein.
It activates an activator protein.
The molecular nature of transposable elements was first understood in E. coli due to the simplicity of the E. coli genome. Which of the following types of transposable element contribute significantly to the genome complexity of eukaryotic organisms? Genes LINES SINES IS elements LTR retrotransposons
LINES SINES LTR retrotransposons
What is the difference between a missense mutation and a nonsense mutation?
Missense mutations alter the coding sequence so that one amino acid is substituted for another. Nonsense mutations change a codon originally specifying an amino acid into a translation termination codon.
Transposable elements are also known as: Group of answer choicesMoving genesMobile genetic elementsTransformersJumping genesJumping repeats
Mobile genetic elements Jumping genes
Mutations may exert a variety of effects on living systems. List at least three categories of mutations based on their biological effects.
Morphological, nutritional or biochemical and behavioral mutations.
Some mutagens cause genetic changes that can be "corrected" by re-exposing cells to the same mutagen. Other mutagens do not behave in this way. Provide one example of each of these two types of agents and describe the mutational changes caused in DNA. Explain why some mutagens behave in one way, while others do not.
Mutagens that cause base substitutions are "corrected" by mutagens of the same class (nitrous acid, 2-aminopurine, and 5-bromouracil). Frameshift mutations, caused by proflavin or acridine orange are "corrected" by the same class of frameshift mutagens, but not by mutagens that cause base substitutions. X rays cause major structural changes in chromosomes (deletions, translocations, etc.) and are not "corrected" by any mutagen, including X rays.
How might one generate a line of male mice that contain two X chromosomes?
Nondisjunction during meiosis to cause two X's and one Y
E. coli bacteria are placed into a medium containing glucose and lactose. Which of the genes below do you expect to be turned on? Lac I None of the above Permease Lac P f-galactosidase
None of the above
Transcription factors appear to be important molecules relating to the regulation of gene activity. Regarding eukaryotes, two general classes of transcription factors exist. Briefly describe each.
One class assembles at promoter regions adjacent to the site of transcription. Activator and Repressor. Recruitment of an activator to a promoter results in increased gene expression. Recruitment of a repressor leads to decreased gene expression. The other class binds at more distant regions enhancers, silencers
How might gene targeting be used to help understand the function of a given gene?
One could use gene targeting to remove a specific part of a gene (ie. an exon) to observe how a change in structure affects its function.
_____________ are complexes where, among other activities, a great deal of RNA degradation takes place.
P bodies
P-element transposons provide a powerful tool for the study of Drosophila genetics. What are P elements, and why are they so useful?
P-element transposons are mobile genetic elements that can move in and out of the genome. A transposase enzyme recognizes and acts on 31 bp inverted repeats at each end of the P element. Genetically engineered P elements can be injected into eggs, which enables the P-element bearing gene to be inserted into the embryo's DNA. With proper markers, the flies bearing the modified element can be recognized and transformed and mosaic flies may pass the element in the germ cells. P-elements can also be used to generate mutations by inserting into genes, thus disrupting their function.
What is meant by the term photoreactivation repair?
Photoreactivation repair, discovered in 1949, is a process described in E. coli in which UV-induced DNA damage can be partially reversed if cells are briefly exposed to light in the blue range of the visible spectrum.
What is the difference between positive and negative control? What is the difference between inducible and repressible operons?
Positive transcriptional control requires an activator protein to stimulate transcription at the operon. In negative control, a repressor protein inhibits or turns off transcription at the operon. An inducible operon normally is not transcribed. It requires an inducer molecule to stimulate transcription either by inactivating a repressor protein in a negative inducible operon or by stimulating the activator protein in a positive inducible operon. Transcription normally occurs in a repressible operon. In a repressible operon, transcription is turned off either by the repressor becoming active in a negative repressible operon or by the activator becoming inactive in a positive repressible operon.
_______________ is also known as RNA silencing and posttranscriptional gene silencing.
RNA interference
What is the general mechanism by which gene expression in eukaryotes is influenced by the extracellular environment?
RNA signaling endocrines and paracrines
What different results can be expected in a mutagenesis experiment that uses radiation as compared with site-directed mutagenesis?
Radiation will cause random mutations while site directed mutagenesis will cause specific targeted mutations
In some cases, genes undergo amplification (local, multiple duplications) when additional gene products are in high demand. Would you consider gene amplification as a form of genetic regulation in eukaryotes?
Since gene amplification involves an increase in the number (copies) of genes, which, in turn, provides the potential for increasing the amount of a gene product because more copies of a given gene are present, one would probably consider gene amplification as a form of genetic regulation. Amplification of ribosomal genes during oogenesis in Xenopus and chorion genes in Drosophila are examples.
What is the Ames test, and how does it work?
The AMES test utilizes two Salmonella typhimurium mutant strains that are both his- to test for mutagenicity. The compounds are modified by liver enzymes prior to the test to allow for possible mutagens to be expressed. The test tubes are plated and if there are more colonies present with a chemical added, a mutagen is present, but if there are no increase in colonies with the chemical added, it is not mutagenic.
The human metallothionein IIA gene (hMTIIA) is transcriptionally regulated through the interplay of regulatory elements and transcription factors. What is the function of this gene, and how is it regulated by environmental circumstances?
The gene hMTIIA produces a protein that binds to heavy metals and protects cells from their toxicity. The gene is transcribed at low levels in all cells but is induced to express at high levels in cells exposed to heavy metals.
How might in situ hybridization aid in determining the tissue-specific and/or temporal-specific pattern of gene expression? Describe the process of in situ hybridization in your answer.
The in situ hybridization uses a labeled complementary RNA strand to localize a specific mRNA sequence in a tissue. Since it uses RNA, it would show proteins expressed, not all genes, and so could show genes expressed in a specific tissue or genes that interact at certain times in development. (??)
Explain why mutations in the lacI gene are trans in their effects, but mutations in the lacO gene are cis in their effects.
The lacI gene encodes the lac repressor protein, which can diffuse within the cell and attach to any operator. It can therefore affect the expression of genes on the same or different molecules of DNA. The lacO gene encodes the operator. It affects the binding of DNA polymerase (OR the lacI repressor) to the DNA, and therefore affects only the expression of genes on the same molecule of DNA.
What experimental results would indicate that the mutation lacIs is dominant to lacI+?
The observation that lacIs is a trans-acting superrepressor and represses the operator on both sides of the DNA sequence, while lacI+ still has variable regulation (for example: transcription is off when lactose is not present, but transcriptionis on when lactose is present.)
Explain how one would use epistasis analysis to determine order of gene action in genetic networks?
The order of action of genes in a regulatory hierarchy that is governed by a signal can often be determined by the method of epistasis analysis, in which the phenotype of a double mutant is compared with that of single mutants. The epistatic mutation may be in either the upstream or the downstream gene, depending on the nature of the two mutations and the type of regulation. Nevertheless, when the regulatory hierarchy satisfies certain conditions, simple rules allow the position of the epistatic locus in the pathway to be determined without detailed knowledge of the nature of the mutations, the pathway, or the molecular mechanism of regulation
Provide a general set of statements that describe enhancers.
The position of an enhancer need not be fixed; it can be upstream, downstream, or within the gene it regulates. It is orientation independent and can act at large distances from the promoter.
Which of the below is not true about the location of enhancers? They can be found downstream of the promoter. They can be found 3' of the polyadenylation site. They can be found upstream of the transcription initiation site. The position of the enhancer has no effect on gene regulation. They can be found in introns.
The position of the enhancer has no effect on gene regulation.
Monod discovered that if tryptophan is present in relatively high quantities in the growth medium, the enzymes necessary for its synthesis are repressed. How does this occur?
Tryptophan acts as a corepressor to activate the tryptophan repressor protein; it is also involved in an attenuation system, which causes the termination of transcription.
Assume that you are working with a mutant, nutritionally deficient strain of Escherichia coli and that you isolate "revertants," which are nutritional-normal. Describe, at the molecular level, two possible causes for the "reversion to wild type."
Two general classes of events could be involved: true reversion or suppression. True reversion would involve a precise correction of the original mutation. Suppression could be intragenic or intergenic. In intragenic suppression, a change in some other part of the mutant gene product serves to "compensate" for the original mutation. In intergenic suppression, a mutation in some other gene, such as a transfer RNA, serves to "compensate" for the original mutation.
In what way do upstream activator sequences (UASs), regulatory sequences in yeast, differ from enhancers and silencers? Enhancers only function downstream. UASs can only function in the 5'-3' direction. UASs function in the middle of transcription units. UASs only function upstream. UASs only function downstream.
UASs only function upstream.
Describe the phenomenon of photoreactivation repair.
UV-induced DNA damage, specifically pyrimidine dimers, can be partially reversed if cells are briefly exposed to light in the blue range of the visible spectrum
Describe the use of DNA databases to characterize a cloned and sequenced gene whose function is unknown.
Various databases allow investigators access to a variety of comparison programs that search for regions of homology to other known sequences. When a homologous gene is identified, its function may already be known from work on another organism, thus providing hints about function. A particular DNA sequence can be "translated" into the sequence of a protein product, and that amino acid sequence can be compared with other proteins in databases such as SwissProt. BLAST searches allow researchers to search protein sequences for regions of homology in other proteins, which may indicate likely function.
Regarding the tryptophan operon, trpR- maps a considerable distance from the structural genes. The mutation either inhibits the interaction with tryptophan or inhibits repressor formation entirely. In the presence of tryptophan in the medium, would you expect the tryptophan operon to be transcriptionally active in this mutant? Explain.
With either of the two scenarios mentioned in the problem, absence of repressor function in a repressible system means that there would be no repression of the operon. The operon would be transcriptionally active.
What human condition is caused by the inability to repair UV-induced DNA lesions?
Xeroderma pigmentosum
Targeted gene knockouts involve the deletion or disruption of a given gene. What method might be effectively used to knock out a gene in yeast? What method might be used in mice? Why would the method used in yeast be ineffective in mice?
Yeast: New segments are attached to the ends of DNA; homologous recombination occurs and the resulting colonies lack the target gene to gain some insight on the function of that gene Mice: The homologous recombination part is identical to that of yeast, however embryonic stem cells are used after to further achieve a mutated mouse by allowing those mutated cells to grow and eventually reproduce offspring expressing the mutated phenotype in hopes to understand its effect The yeast method might be ineffective in mice because we do not want just one mutated cell, we want a whole mutant mouse, as only with the complete organism can we make a full assessment of the effect of the gene inactivation on the phenotype
What are zinc fingers, and why are they frequently encountered in descriptions of genetic regulation in eukaryotes?
Zinc fingers consist of amino acid sequences containing two cysteine and two histidine residues at repeating intervals. Interspersed cysteine and histidine residues covalently bind zinc atoms, folding the amino acids into loops (zinc fingers). They are one of the major groups of eukaryotic transcription factors. They were originally discovered in the Xenopus transcription factor TFIIA, and this structural motif has been identified in a variety of significant regulatory circumstances, including proto-oncogenes and developmental control genes in Drosophila.
One speaks of UAS (upstream activating sequences) as being DNase hypersensitive. We would interpret this to mean that a UAS is constitutively open. any given UAS is composed of a double-stranded site with a bound repressor. each UAS is likely to be single-stranded. more than one strand of DNA exists in each UAS. each UAS has more histone binding sites than non-UAS sites.
a UAS is constitutively open.
Conditional mutations are more likely to result from which of the following alterations to the coding region of a gene. a mutation caused by a deletion a mutation caused by a base addition a mutation caused by X rays a mutation caused by a base addition or deletion a mutation caused by a tautomeric shift
a mutation caused by a tautomeric shift
What modification neutralizes the charges on histones that promote ionic interaction with DNA? phosphorylation acetylation demethylation polyadenylation
acetylation
Assuming one mutational event in a gene, on average, which of the following mutagens would be expected to cause the most damage to a protein synthesized by such a mutagenized gene? ethylmethane sulfonate 2-amino purine acridine orange 5-bromouracil
acridine orange
DNA methylation may be a significant mode of genetic regulation in eukaryotes. Methylation refers to altering translational activity especially of highly methylated tRNAs. changes in DNA-DNA hydrogen binding. altering RNA polymerase activity by methylation. addition of methyl groups to the cytosine of CG doublets. alteration of DNA polymerase activity by addition of methyl groups to glycine residues.
addition of methyl groups to the cytosine of CG doublets.
After translation, eukaryotic proteins can be modified by the removal of amino acids. all of the above. acetylation. the addition of methyl groups. the addition of phosphate groups.
all of the above.
Describe alternative splicing. What is the results of these mechanisms?
alternative splicing is the differential splicing of alternative eons from an initial pre-mRNA transcript. The result is that the possible proteins that a cell can produce is far larger than the number of genes in the genome.
In what part of the mRNA does degradation generally begin? Removal from either end is equally likely. at the 3' end with the removal of the methyl cap at the 5' end with the removal of the methyl cap at the 3' end with the removal of the poly(A) tail at the 5' end with the removal of the poly(A) tail
at the 3' end with the removal of the poly(A) tail
Frameshift mutations are caused by the __________ or __________ of one or more nucleotides in DNA. a. chemical modification b. removal c. reversion d. insertion e. suppression
b,d
The lac repressor protein controls expression of the lac operon via ________________ binding to the lac operator site to repress expression binding to the lac structural genes to repress expression binding of the lac Z and lac Y genes only all of the above binding to the lac promoter site to repress expression
binding to the lac operator site to repress expression
Compare and contrast positive and negative control of gene expression in bacteria.
both forms of control result from an interaction of a molecule with the genetic material (RNA or DNA). Positive control results when the interaction stimulates transcription, whereas negative control occurs when the interaction inhibits transcription.
An insulator is also known as a(n) __________________ .
boundary element
This process moves a nucleosome from the TATA box of a gene's promoter so that transcription can occur.
chromatin remodeling
Proteins that affect chromatin structure without altering histone chemical structure are called _______________.
chromatin remodeling complex
This term describes genetic elements that affect other elements only when they are located adjacent to them. For example, the operator has this effect on its structural genes.
cis-acting
Which of the following clusters of terms applies when addressing enhancers or silencers as elements associated with eukaryotic genetic regulation? cis-acting, fixed position, fixed orientation trans-acting, fixed position, fixed orientation cis-acting, variable position, fixed orientation trans- and cis-acting, variable position cis-acting, variable orientation, variable position
cis-acting, variable orientation, variable position
The isolation of cell-cycle mutations in yeast was greatly facilitated by the use of _______________ mutations, which allow investigators to study the effects of mutations that would be lethal if expressed constantly.
conditional
Mutations in the lacI and lacO genes in the lactose system often lead to full production of the three structural genes related to the lac operon even with no lactose available to the organism. Such mutations would be called________.
constitutive mutations
When considering the binding of cAMP-CAP and RNA polymerase to the lacoperon, both bind more efficiently than either singly. What term is applied to this increased efficiency of binding?
cooperative
Regarding regulation of the tryptophan operon, what type of regulatory molecule might one appropriately call the amino acid tryptophan?
corepressor
Transcriptional repression by methylation of DNA is most common in sequences called____________ islands.
cpG
Mutations in the promoter region of the b-globin gene indicate that some areas are more sensitive than others. When mutations occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box) transcription ________________.
decreases
Name two chemical mutagens that are collectively called acridine dyes.
dibenzopyridine, 2,3-benzoquinoline
The process by which excessive numbers of a sex chromosome are corrected, often by methylating the X chromosome to form a Barr body.
dosage compensation
To use RNAi (RNA interference) as a research tool, investigators introduce short synthetic __________ RNA into cells.
double-stranded, small interfering
Maternal effects are cases of extrachromosomal inheritance in which the genotype of the mother influences the phenotype of her immediate offspring in a non-Mendelian manner. Explain the general molecular basis of a maternal effect.
during development of the egg, females provide numerous nutritional and informational substances, which direct and support early embryonic development. these substances are often in the form of transcription factors, receptors, mRNA, and proteins, although some other substances are likely. In some cases, these maternally supplied substances override the actual genotype of the zygote and produce a phenotype much like the genotype of the mother.
Match each number with the closest type of DNA: a. moderately repetitive DNA b. highly repetitive DNA c. short interspersed elements d. long interspersed elements e. unique-sequence DNA Reference: Ref 11-1 gene-encoding sequence
e
Considering the location of genes in the interphase nucleus, certain chromosomal territories appear to exist. Specifically, even-numbered chromosomes are located in the interior of the nucleus, whereas odd-numbered chromosomes are located peripherally. each chromosome appears to occupy a discrete domain. gene-poor regions of chromosomes are located outside the nucleus, whereas gene-rich regions are located inside the nucleus. small chromosomes are more likely to be located in the center of the nucleus. large chromosomes are more likely to be located in the center of the nucleus.
each chromosome appears to occupy a discrete domain.
Considering the location of genes in the interphase nucleus, certain chromosomal territories appear to exist. Specifically, gene-poor regions of chromosomes are located outside the nucleus, whereas gene-rich regions are located inside the nucleus. even-numbered chromosomes are located in the interior of the nucleus, whereas odd-numbered chromosomes are located peripherally. large chromosomes are more likely to be located in the center of the nucleus. each chromosome appears to occupy a discrete domain. small chromosomes are more likely to be located in the center of the nucleus.
each chromosome appears to occupy a discrete domain.
What is the function of the lacY gene in the lactose operon?
encodes lactose permease, a membrane embedded transporter that allows lactose to be transported into the cell
A eukaryotic DNA sequence that affects transcription at distant promoters is called a(n) ________________.
enhancer
Regulation of gene expression using siRNAs is found in eukaryotes only. prokaryotes and eukaryotes. prokaryotes only.
eukaryotes only.
Regulation of gene expression using siRNAs is found in prokaryotes only. prokaryotes and eukaryotes. eukaryotes only.
eukaryotes only.
Regarding the nature of the ABO blood groups, dysfunction in what process leads to the O blood type?
failure to modify the H substance due to lack of glycosyltransferase activity
A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be the following: transition. recombinant. base analog. transversion. frameshift.
frameshift
When X rays penetrate cells, electrons are ejected from atoms of molecules. Stable molecules can be transformed into what types of hazardous materials?
free radicals
Define gene regulation. What are three ways gene regulation can be controlled in a cell?
gene regulation is defined as the control of a gene's transcript and its protein product. it can be achieved by altering either the transcription of the gene at RNA level, the translation of the protein from that transcript, or by altering the structure of DNA such that transcription can't occur.
Regarding the lactose utilization system in E. coli, a ___________ inducer is a molecule that is chemically analogous to lactose, induces the operon, but is not a substrate for the enzymes of the lac operon.
gratuitous
A highly-methylated region of a chromosome that has become largely deactivated and can be seen as dense-regions when viewed using electron microscopy.
heterochromatin
When siRNAs or miRNAs are present, the rate of mRNA degradation_____________ , and the rate of protein production ___________.
increases, decreases
Since the binding of the _________ to the _________ prevents it from binding to DNA by causing a conformational change in its structure, it is called an _________ protein. Separate your answers with commas.
inducer,repressor,allosteric
Channels between chromosomes in the interphase nucleus are called nonlocalized zones. extrachromosomal elements. localized zones. interchromosomal compartments subchromosomal territories.
interchromosomal compartments.
A mutant E. coli strain, grown under conditions that normally induce the lac operon, produces high amounts of ß-galactosidase. What is a possible genotype of the cells? lacI+ lacP+ lacOc lacZ+ lacY+ lacA+ lacI- lacP+ lacO+ lacZ- lacY+ lacA+ lacI+ lacP+ lacO+ lacZ- lacY+ lacA+
lacI+ lacP+ lacOc lacZ+ lacY+ lacA+
A mutant E. coli strain, grown under conditions that normally induce the lac operon, does not produce ß-galactosidase. What is a possible genotype of the cells? lacI+ lacP- lacO+ lacZ+ lacY+ lacA+ lacI+ lacP+ lacOc lacZ+ lacY+ lacA+ lacl+ lacP+ lacO+ lacZ+ lacY+ lacA+ lacI+ lacP+ lacO+ lacZ+ lacY- lacA+
lacI+ lacP- lacO+ lacZ+ lacY+ lacA+
Constitutive mutations may occur in various components of the lac operon. Name two genes of the lac operon in which constitutive mutations could occur.
lacOc and lacI-
The lac repressor binds to: RNA polymerase. d-galactosidase, permease and transacetylase. lactose and DNA. promoter and lactose. RNA polymerase and DNA.
lactose and DNA.
Of the two cell lines that can contain a mutation in an organism, the __________ is most consequential to subsequent generations.
latter
Within the control region of the tryptophan operon is a section of DNA that is sensitive to levels of tryptophan in the system. What is the name of this region?
leader or attenuator region
Which of the following are general categories of mutations? Select all that apply. protein DNA lethal behavioral conditional
lethal behavioral conditional
Which of these are major structural classifications of DNA-binding domains that are found in eukaryotic transcription factors? Please select all that apply: promoters leucine zipper zinc finger coil-coil helix-turn-helix
leucine zipper zinc finger helix-turn-helix
Attenuation involves the termination of ______ synthesis
mRNA
How are miRNAs produced? How do miRNAs function to affect production of proteins? Provide sufficient detail in your answer for full credit.
miRNAs are small RNA molecules transcribed from within and organisms genome. They are further processed after transcription by Dicer protein into small dsDNA molecules. These small dsDNA molecules are targeted to the RISC proteins where they are unwound into single stranded RNAs. These ssRNAs are then able to inhibit translation from mRNAs in a number of ways including inhibition of translation, targeting mRNAs for degradation, or sequestration of mRNAs.
High-throughput technologies such as DNA and protein expression _________ are often used to provide a global picture of gene expression
microarrays
Which of the following are general categories of mutations? Select all that apply. Group of answer choices morphological induced protein-altering DNAregulatory
morphological induced protein-altering
What is a significant drawback to using the mouse as a model organism compared with Drosophila?
mutations can be generated more easily in drosophila genetic manipulations are so much easier in Drosophila and mice take longer to reproduce
Under a system of ______________, genetic expression occurs unless such expression is shut off by some form of regulator.
negative control
What term would be applied to a regulatory condition that occurs when protein greatly reduces transcription when associated with a particular section of DNA? inhibition positive control stimulation activation negative control
negative control
What term would be applied to a regulatory condition that occurs when protein greatly reduces transcription when associated with a particular section of DNA? inhibition positive control stimulation negative control activation
negative control
What term would be applied to a regulatory condition that occurs when protein greatly reduces transcription when associated with a particular section of DNA? positive control inhibition stimulation activation negative control
negative control
An operon is controlled by a repressor. When the repressor binds to a small molecule, it is released from binding to DNA near the operon. The operon is never expressed if a mutation prevents the repressor from binding to the small molecule. negative repressible positive inducible positive repressible negative inducible
negative inducible
An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operon. The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule. negative repressible negative inducible positive repressible positive inducible
negative repressible
An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operon. The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule. positive inducible negative inducible positive repressible negative repressible
negative repressible
What are the differences between neutral mutations and silent mutations?
neutral mutations are changes in DNA sequence that alter the amino acid coding sequence of a polypeptide, but do not change its biological function. silent mutations are changes in the DNA sequence that produce synonymous codons specifying the same amino acid as the original, non-mutated sequence.
A _________ mutation changes a codon that specifies an amino acid into one that terminates translation. silent nonsense reverse neutral
nonsense
A constitutive gene is _______ regulated and is expressed ____________.
not,continually
Loss-of-function mutations that eliminate the function of a gene product are also known as _____ mutations or gene knockouts.
null
What are null mutations? What classes of mutagens would most likely generate null mutations?
null mutations causee complete lack of function and no production of functional gene product. frameshift mutations
What term refers to a contiguous genetic complex that is under coordinate control? operon allosteric prototroph lysogen attenuation
operon
What term refers to a contiguous genetic complex that is under coordinate control? operon attenuation allosteric lysogen phototroph
operon
A conditional mutation is one that allows a mutant gene product to function normally under the ________ condition, but to function abnormally under the ________ condition. Such mutations are especially useful for the study of ________ mutations. permissive; restrictive; dominant restrictive; permissive; dominant dominant; recessive; semidominant recessive; dominant; codominant permissive; restrictive; lethal
permissive; restrictive; lethal
Degradation of a eukaryotic mRNA is generally preceded by shortening of the _____________.
poly a tail
The ____________________ stabilizes the 5' cap, which must be removed before the mRNA molecule can be degraded from the 5' end.
poly(A) tail
A catabolite-activating protein (CAP) exerts _____________control over the lac operon.
positive
When transcription factors interact with DNA, is the resulting genetic control typically positive or negative?
positive
Which of the following terms best characterizes catabolite repression associated with the lactose operon in E. coli? inducible system repressible system constitutive positive control negative control
positive control
Which of these is a level or type of genetic regulation in eukaryotes? Select all that apply: Group of answer choices post-translational DNA methylation transcriptional RNA splicing co-transcriptional
post-translational DNA methylation transcriptional
This is the region of a gene where RNA polymerase binds to initiate transcription.
promoter
Describe the function of promoters in eukaryotes. Where are they usually located, relative to the corresponding gene (give a quantitative answer in base-pairs)? What two sequence elements do they normally possess?
promoter regions are necessary for the initiation of transcription. promoters that interact with RNA polymerase II are usually location within 100 bp upstream of a gene and usually contain a TATA box (-25 to -30) and a CAAT box (-70 to -80)
What is the general position of the consensus sequence called the GC box? What is its sequence? Group of answer choices terminator; GGGCGG promoter; GGGCGG terminator; CAAT promoter; CAAT attenuator; GGGCGG
promoter; GGGCGG
What are the basic regulatory elements in a strand of DNA that allow for genes to be regulated? Are these different in eukaryotes and prokaryotes? If so, how?
promoters and operators in prokaryotes promoters, proximal promoter elements, enhancers, and silencers in eukaryotes eukaryotic transcription is different in that prokaryotic genes are transcribed as operons, but eukaryotic genes are not. the role of the nucleosome is different in eukaryotic transcription as well
The process of error correction of mismatched bases carried out by DNA polymerases is called
proofreading
Apurinic sites (AP sites) involve a spontaneous loss of ________ in an intact double-helix DNA molecule.
purine
Recombinational repair is activated when damaged DNA has escaped repair and the distortion disrupts the process of replication; which is dependent on the product of the ________ gene.
recA
Transcription factors are proteins with at least two functional _________
regions
An example of a gene product encoded by a regulatory gene is beta-galactosidase enzyme. allolactose. operator. repressor protein
repressor protein
The __________ is a type of _________ protein that binds to a region of DNA in the promoter of a gene called the _________ and prevents transcription from taking place in bacteria. Separate your answers with commas.
repressor,regulatory,operator
mRNAs are degraded by enzymes called ____________.
ribonuclease
The ________ the wavelength of a radiation source, the greater its likelihood of causing damage.
shorter
Regions of chromosomes that are inactivated through methylation are termed this.
silent chromatin
Under what condition(s) might one have an amino acid substitution in a protein that does not result in an altered phenotype?
silent mutations
Under certain conditions, the rate of mutation of a particular gene may be determined in humans. What properties of the mutation would favor the most direct determination of mutation rate in humans? Select all that apply: single locus dominant fully expressed 100% penetrant recessive
single locus dominant fully expressed 100% penetrant
In the lactose operon, the product of structural gene lacZ is capable of nonautonomous replication. forming ATP from pyruvate. replacing hexokinase in the early steps of glycolysis. forming lactose from two glucose molecules. splitting the β-linkage of lactose.
splitting the β-linkage of lactose.
Mutations that arise in nature, from no particular artificial agent, are called cosmic mutations. spontaneous mutations. chromosomal aberrations. natural mutations. induced mutations.
spontaneous mutations.
In general, a "model organism" used in genetics studies is one in which there is a large body of genetic knowledge that has been compiled over decades of genetic research. In addition, model organisms have available their DNA sequences and collections of ________ that make detailed genetic analysis possible and efficient. incomplete metamorphic systems complete metamorphic systems museum specimens strains with specific mutations epigenetic developmental systems
strains with specific mutations
In general, a "model organism" used in genetics studies is one in which there is a large body of genetic knowledge that has been compiled over decades of genetic research. In addition, model organisms have available their DNA sequences and collections of ________ that make detailed genetic analysis possible and efficient. strains with specific mutations complete metamorphic systems museum specimens epigenetic developmental systems incomplete metamorphic systems
strains with specific mutations
DNA may be damaged from the by-products of normal cellular aerobic respiration. Name three of these electrophilic oxidants that are generally classified as reactive oxidants. carboxyls (COOH-) superoxides (O2·-) hydrogen peroxide (H2O2) hydroxyl radicals (·OH) carbon dioxide (CO2)
superoxides (O2·-) hydrogen peroxide (H2O2) hydroxyl radicals (·OH)
siRNAs and miRNAs are produced by the cutting and processing of double-stranded RNA by Dicer enzymes. the cleavage of functional mRNA within the cytoplasm. the cleavage of pre-mRNA in the nucleus. the cutting and processing of double-stranded RNA by Slicer enzymes. the cleavage of RISCs by endonucleases.
the cutting and processing of double-stranded RNA by Dicer enzymes.
When referring to attenuation in regulation of the tryptophan operon, it would be safe to say that when there are high levels of tryptophan available to the organism, the tryptophan operon is being transcribed at relatively high levels. ribosomes are stalling during translation of the attenuator region. translational termination is likely. tryptophan is inactivating the repressor protein. transcriptional termination is likely.
transcriptional termination is likely.
It is possible for a repressor to negatively regulate the expression of an operon because the repressor binding site overlaps the promoter site of the operon allowing it to physically block the binding of RNA polymerase. the repressor induces the expression of inducer. the repressor binding site on the DNA overlaps with the translation start site. one of the genes expressed in the operon negatively regulates the repressor.
the repressor binding site overlaps the promoter site of the operon allowing it to physically block the binding of RNA polymerase.
Insulators can block the effects of enhancers only when they lie within the structural genes. they lie adjacent to a promoter. they lie between an enhancer and a promoter. they lie upstream of a promoter. they lie within a consensus sequence.
they lie between an enhancer and a promoter.
Nutritional mutations can be defined as those mutations which result in changes in behaviour. all strains which are not auxotrophic. those mutations which do not allow an organism to grow on minimal medium, but do allow the organism to grow on complete medium. those mutations which change the composition of the medium.
those mutations which do not allow an organism to grow on minimal medium, but do allow the organism to grow on complete medium.
Genetic regulation in eukaryotes can take place at a variety of levels from transcriptional to post-translational. At what level is genetic regulation considered most likely in prokaryotes? intron processing capping polyadenylation of the 3' end of the mRNAs transcriptional
transcriptional
Genetic regulation in eukaryotes can take place at a variety of levels from transcriptional to post-translational. At what level is genetic regulation considered most likely in prokaryotes? transcriptional capping intron processing exon processing polyadenylation of the 3' end of the mRNAs
transcriptional
____________________act as intermediaries between ______________________________ and specific _____ sequences to modify chromatin structure and activate transcription.
transcriptional activators, chromatin remodeling complexes, DNA
Regarding eukaryotic and prokaryotic genetic regulation, what process seems to be the most similar between the two? RNA splicing regulation transcriptional regulation intron/exon shuffling 5'-capping regulation poly(A) tail addition
transcriptional regulation
Regarding eukaryotic and prokaryotic genetic regulation, what process seems to be the most similar between the two? transcriptional regulation poly(A) tail addition 5'-capping regulation intron/exon shuffling RNA splicing regulation
transcriptional regulation
When referring to attenuation in regulation of the tryptophan operon, it would be safe to say that when there are high levels of tryptophan available to the organism, transcriptional termination is likely. translational termination is likely. tryptophan is inactivating the repressor protein. the tryptophan operon is being transcribed at relatively high levels. ribosomes are stalling during translation of the attenuator region.
transcriptional termination is likely.
Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are called transversions and transitions. base analogs and frameshift. euchromatic and heterochromatic. sense and antisense. error prone and spontaneous.
transversions and transitions.
Considering the electromagnetic spectrum, identify likely mutagens from the following list: radio waves, microwaves, infrared, ultraviolet, X rays, gamma rays, cosmic rays. Select all that apply: infrared ultraviolet microwaves gamma rays X-rays cosmic rays
ultraviolet gamma rays X-rays cosmic rays
The following may be caused by mobile genetic elements except ________________ disrupt a gene activate a gene in which they reside cause chromosome breaks all of the above undergo mutation
undergo mutation
A(n) _______________ can function at variable distances and in either orientation. However, it differs from an enhancer in that it cannot function downstream of the transcription starting point.
upstream activator
Under the system of genetic control of the tryptophan operon, when there are high levels of tryptophan in the medium, transcription of CAP (CRP) occurs at high levels. no transcription occurs under any nutritional circumstance because negative controls inhibit transcription. when there are high levels of tryptophan in the medium, transcription of the trp operon occurs at high levels. when there is no tryptophan in the medium, transcription of the trpoperon occurs at high levels. when there are high levels of tryptophan in the medium, ribosomes "stall" and reduce the levels of tryptophan synthesized.
when there is no tryptophan in the medium, transcription of the trpoperon occurs at high levels.
