module 4 extended and short answer pt.2

(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.

(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

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 1. high glucose, no lactose 2. no glucose, high lactose 3. high glucose, high lactose 4. no glucose, no lactose

- + - -

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

Strain genotype Lactose absent Lactose present 1. lacI+ lacP+ lacO+ lacZ+ lacY+ 2. lacI+ lacP+ lacOc lacZ+ lacY+ 3. lacI+ lacP+ lacOc lacZ- lacY+ 4. lacIs lacP+ lacOc lacZ+ lacY+ 5. lacI- lacP+ lacO+ lacZ+ lacY+ / lacI+ 6. lacIs lacP+ lacO+ lacZ+ lacY+/ lac I+

1. - + 2. + + 3. - - 4. + + 5. - + 6. - -

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 of mRNA stability 5. Regulation of translation 6. Regulation by pos -translational modification of the synthesized protein

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 Strain genotype Lactose absent Lactose present 1 - + 2 + + 3 - -

1. lacI+ lacP+ lacO+ lacZ+ lacY+ 2. lacI+ lacP+ lacOc lacZ+ lacY+ OR lacI- lacP+ lacO+ lacZ+ lacY+ 3. lacI+ lacP- lacO+ lacZ+ lacY+

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.

List at least three different types of DNA repair and briefly explain how each is carried out.

2. Direct repair. DNA damage is repaired by directly changing the damaged nucleotide back to its original structure. 3. Base excision repair. The damaged base is excised, and then the entire nucleotide is replaced. 4. Photo reactive repair - reversal of pyrimidine dimers formed by uv light exposure. Requires the photoactivation enzyme

What is the approximate genome size in the mouse, and how many chromosomes are present?

23,000 genome size, 20 chromosomes

Present a description of the molecular mechanism of the mutagenic action of any two of the following mutagens: 5-bromouracil, proflavin, ultraviolet light.

5-bromouracil is an analog of thymine, which anomalously pairs with guanine. Proflavin adds or removes single bases from DNA, thus causing frameshift mutations. Ultraviolet light causes thymine dimers.

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.

Three human disorders-fragile X syndrome, myotonic dystrophy, and Huntington disease-are conceptually linked by a common mode of molecular upset. Describe the phenomena that link these disorders.

All three are caused by disparate genes, but each gene was found to contain repeats of a unique trinucleotide sequence. In addition, the number of repeats may increase in each subsequent generation (genetic anticipation).

The _________ can be used to quickly screen chemicals for their ability to be mutagenic (and hence potentially carcinogenic).

Ames test

Compare and contrast positive and negative control of gene expression in bacteria.

Both forms of control result from an interaction of a molecule (usually considered to be a protein) with the genetic material (either RNA or DNA). Positive control results when the interaction stimulates transcription, whereas negative control occurs when the interaction inhibits transcription.

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 other substances are also likely (substrates and products). 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.

Parts of chromosomes that are not methylated for inactivation, but rather are less dense-staining and are likely active in transcription in the cell.

Euchromatin

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.

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

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.

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.

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 Drosophila many maternal-effect genes have been identified.

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.

Inducer, repressor, allosteric

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

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? select all that apply

LINES, SINES, LTR retrotransposons

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.

What is meant by polycistronic mRNA? Give an example.

Polycistronic mRNA can be translated in to more than one protein. The tryp operon is an example.

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 located within 100 bp upstream of a gene and usually contain a TATA box (-25 to -30) and a CAAT box (-70 to -80).

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, operators in prokaryotes. Promoters, proximal promoter elements, enhancers, and silencers in eukaryotes. Eukaryotic transcription is different in a few ways, most notably in that prokaryotic genes are transcribed as operons, while eukaryotic genes are not. In addition, the role of the nucleosome is different in eukaryotic transcription.

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 significance of the homeodomain?

The homeodomain is a highly conserved protein of 60 amino acids found in a variety of organisms, which, in conjunction with other factors, is thought to play a role in DNA binding and transcriptional activation.

Approximately 5% of the cytosine residues are methylated in the genome of any given eukaryote. In what way is DNA methylation related to genetic regulation?

There is an inverse relationship between the degree of methylation of eukaryotic DNA and the degree of gene expression

Describe the general structure of a transcription factor. What two domains do transcription factors tend to have?

Transcription factors have a activation domain and a DNA binding domain

____________________act as intermediaries between ______________________________ and specific _____ sequences to modify chromatin structure and activate transcription.

Transcriptional activators, chromatin-remodeling complexes, DNA

State whether the following statement is true or false; then give your reasoning. The terminating "hairpin" loop occurs in the tryptophan operon when sufficient tryptophan is present.

True. When sufficient tryptophan is present, the transcrption of the trp gene, with an attenuator sequence, located between the mRNA leader sequence and trp operon sequence makes ribosomes to translate the attenuator sequence domains 1 and 2, allowing domains 3 and 4 to form a hairpin structure, which results in termination of transcription of the trp operon.

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.

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 Sequence (UAS)

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?

When the RNA molecules are small RNA (siRNA and/or miRNA), which are capable of RNA silencing or posttranscriptional gene silencing. Just a few of these small RNA molecules have

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?

When the RNA molecules are small RNA (siRNA and/or miRNA), which are capable of RNA silencing or posttranscriptional gene silencing. Just a few of these small RNA molecules have the ability to silence trascription Using RNAi (RNA interference), one can often systematically knock out the function of a gene. As a research tool, investigators introduce short synthetic double-stranded RNAi molecules into cells. These molecules trigger an RNA-degradation pathway, which targets mRNA for degradation or inhibition

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.

What is meant by a suppressor mutation?

a second mutation that alleviates or reverts the phenotypic effects of an already existing mutation

________ RNA processing generates different mRNAs, which can direct the synthesis of different polypeptides.

alternative

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

A mutation that occurs naturally, without exposure to a known mutagen, is called a ________.

gain of function or spontaneous?

Of the two cell lines that can contain a mutation in an organism, the __________ is most consequential to subsequent generations.

germ line

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

Which of these are major structural classifications of DNA-binding domains that are found in eukaryotic transcription factors? Please select all that apply:

helix-turn-helix zinc finger leucine zipper

Regions of chromosomes that are inactivated through methylation are termed this.

heterochromatin

Attenuation involves the termination of ______ synthesis

mRNA

A constitutive gene is _______ regulated and is expressed ____________.

not, continually

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.

various splicing schemes in the CT/CGRP gene in different tissues. In thyroid tissue, only the first four exons remain, while in the brain exons 5 and 6 includes, but not 4.

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?

when an organism hetrozygous for a pair of allel ("+ -")mutation of the chromosome bearing recessive allel (-),the dominent allel (+) on theother chromosome will became expressed phenotypically. i.e wild type

What human condition is caused by the inability to repair UV-induced DNA lesions?

xeroderma pigmentosum

How might one determine whether a particular suspected gene is capable of causing cancer in mammals when it is overly expressed?

A general method could take the normal gene and, through the use of genetic manipulations such as translocations, inversions, or insertions, place the gene in question next to relatively strong gene promoters and enhancers. One could then introduce the composite gene complex into a mouse to generate a transgenic strain. If the transgene is expressed at high levels, one could determine its influence on the induction of cancer.

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

An allosteric molecule is one in which ________.

binds to the regulatory site

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

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.

The catabolite repression system in E. coli essentially represses the lac operon 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.

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, on the other hand, are changes in DNA sequence that produce synonymous codons specifying the same amino acid as the original, non-mutated sequence.

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.

Enhancers have several structural and functional characteristics that distinguish them from promoters. Describe three such characteristics, focusing on how these traits differ between enhancers and promoters.

Position need not be fixed. Orientation may be inverted without significant effect. They can act at a great distance from the promoter

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.

Define RNA silencing (or interference). Explain how siRNAs arise and how they potentially affect gene expression. How are siRNAs different from the antisense RNA mechanism?

RNA silencing, or RNA interference, occurs when double-stranded RNA molecules are cleaved and processed to produce small single-stranded interfering RNAs (siRNAs). These siRNAs bind to complementary sequences in mRNA molecules, stimulating cleavage and degradation of the mRNA. The siRNAs may also stimulate DNA methylation at DNA sequences complementary to the siRNAs. The paired mRNA-siRNA attracts a protein-RNA complex that cleaves the mRNA in an area bound by the siRNA. Following the initial cleavage, the mRNA is further degraded. The cleavage and subsequent degradation of the mRNA make it unavailable for translation. DNA methylation in the nucleus stimulated by siRNAs also affects transcription. Antisense RNA binds to mRNAs also, but physically interferes with translation.

The following table lists several genotypes associated with the lac operon 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.) Genotype No lactose With lactose a. I + O+ Z+/ F' I + O+ Z+ _________ _________ b. I - Oc Z -/ F' I - Oc Z- __________ _________ c. I - Oc Z +/ F' I - O+ Z+ __________ _________ d. I s Oc Z -/ F' I s O+ Z+ __________ _________

a) -,+ (b) -,- (c) +,+ (d) -,-

Present a detailed description of the actions of the regulatory proteins in a) inducible and b) repressible enzyme systems. Separate and clearly label your answers for parts a-b in the box below.

a) In inducible enzyme systems, a repressor protein is bound to the operator at all times. When a certain molecule is present and binds to the repressor protein, it changes its conformation so that it can no longer bind to the operator. This allows the polymerase to bind and transcription occurs. b) In repressible enzyme systems, a repressor protein is present in the environment, but in the wrong conformation. When a certain molecule is present and binds to the repressor protein, it changes its conformation so that it can bind to the operator. This prevents polymerase from binding and transcription stops.

This structure forms when an extra X chromosome is methylated and largely inactivated. It is most commonly found in females.

barr body

Which of the following are general categories of mutations? Select all that apply

behavioral conditional lethal

An insulator is also known as a(n) __________________ .

boundary element

In what way can 5'-azacytosine influence transcription?

causes undermethylation of sites of incorporation and changes in the pattern of gene expression

Recent discoveries on causes of fragile-X syndrome, myotonic dystrophy, and Huntington disease indicate what type of genetic alteration?

change in trinucleotide repeats

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

A condition in which a gene or group of genes is expressed all the time.

constitutive

Regarding the lactose utilization system in E. coli, a _________ mutant is one in which the three enzymes are produced regardless of the presence or absence of lactose.

constitutive

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

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

Mutations in the promoter region of the β-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 usually ________.

decreases

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

A eukaryotic DNA sequence that affects transcription at distant promoters is called a(n) ________________.

enhancer

The ____________________ consists of modifications to histone proteins that affect the expression of DNA sequences.

histone code

Loss-of-function mutations that eliminate the function of a gene product are also known as _____ mutations or gene knockouts

inactivating?

What symbols are used to describe constitutive mutations in the lac operon?

lacOc,lacIc*

Describe the phenomenon of photoreactivation repair.

mediated by the photoreativation enzyme, which cleaves covalent bonds between dimers

High-throughput technologies such as DNA and protein expression _________ are often used to provide a global picture of gene expression.

microarrays

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

Name at least three different levels of regulation in eukaryotes.

pretranscriptional, transcriptional, processing, transport, translational, posttranslational

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?

protects against heavy metals toxicity and protects against free radicals. the gene will express when human body administrated to heavy metals or under stress conditions.

Apurinic (and apyrimidinic) sites (AP sites) involve a spontaneous loss of ______________ in an intact double-helix DNA molecule

purine

Regarding a gene's DNA sequence, what is meant by a sequence motif?

recurring patterns in DNA that are presumed to have a biological function. Often they indicate sequence-specific binding sites for proteins such as nucleases and transcription factors

The general term for a non-polymerase protein that binds to an operator.

repressor

The ________ the wavelength of a radiation source, the greater its likelihood of causing damage.

shorter

Under what condition(s) might one have an amino acid substitution in a protein that does not result in an altered phenotype?

silent mutations, neutral mutations

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.

situ hybridization uses a labeled complementary RNA strand to localize a specific mRNA sequence in a tissue. This method is widely used to describe the spatial and temporal expression patterns of developmentally regulated genes

What is the Ames test, and how does it work?

tests whether a chemical is a mutagen. The test uses Salmonella bacteria that have a mutation that prevents them from making their own histidine.