MOLGEN 4500 Module 4/5
Name six different levels at which gene expression might be controlled
1. Alteration or modification of the gene structure at the DNA level 2. mRNA stability 3. mRNA processing 4. Transcriptional regulation 5. Translation 6. Post-translational modifications of synthesized proteins
Which of these is a level of regulation in eukaryotes? 1. Transport 2. Processing 3. Post-translational 4. Operon 5. Transcriptional
1. Transport 2. Processing 3. Post-translational 5. Transcriptional
Considering the electromagnetic spectrum, identify likely mutagens from the following list. 1. Radio waves 2. Microwaves 3. Infrared 4. Ultraviolet 5. X-rays 6. Gamma rays 7. Cosmic rays
4. Ultraviolet 5. X-rays 6. Gamma rays 7. Cosmic rays
What is the general position of the consensus sequence called the GC box? What is its sequence?
B. promoter, GGGCGG
Genetic involvement in development appears to be achieved at least in part by variable _________
Gene activity
Describe two mating patterns that have an impact on the genetic composition of a population.
Inbreeding—preferential mating with close relatives Assortative mating—preferential mating with individuals of dissimilar or similar genotype or phenotype.
Explain how inbreeding can have a positive effect on population fitness.
Many deleterious recessive alleles are weeded out by natural or artificial selection so that the population becomes homozygous for beneficial alleles. In this way, the harmful effects of inbreeding may eventually be eliminated leaving a population that is homozygous for beneficial traits.
What functions earlier in development, maternal-effect genes or zygotic genes?
Maternal-effect genes
E. coli lac operon control by lac I
Negative inducible
An example of a gene product encoded by a regulatory gene isle
Repressor protein
A gene which specifies the fate off a particular anatomical segment in Drosophila is called a ________.
Selector gene
What formula can be used to determine the number of categories (phenotypes) possible in the F2 results of a polygenic system?
The correct answer is: 2n+1
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.
According to Hardy-Weinberg, if we know the frequency of each allele in the population, what can we predict?
We can predict what genotypes and phenotypes we should see in the population.
DNA methylation may be a significant mode of genetic regulation in eukaryotes. Methylation refers to
addition of methyl groups to the cytosine of CG doublets.
Which term most appropriately refers to a regulatory protein in prokaryotes? a. Translation b. RNA processing c. DNA binding protein d. Gyrase action e. Helicase activation
c. DNA binding protein
Describe 3 pieces of evidence that supports the hypothesis that DNA methylation is important factor in gene regulation
1. An inverse relationship exists bw 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-azacytidine (which can't be methylated) causes changes in the pattern of gene expression
List at least two different types of DNA repair and briefly explain how each is carried out
1. Mismatch repair; replication errors that are the result of base-pair mismatches are repaired. Mismatch repair enzymes recognize distortions in the DNA structure due to mispairing and detect the newly synthesized strand by the lack of methylation on the new strand. The bulge is excised and DNA polymerase and DNA ligase fill in the gap 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. Photoreactive repair; the reversal of pyrimidine dimers formed by UV light exposure. Requires the photoactivation enzyme 5. Post-replication repair; occurs on damaged DNA that has escaped initial mismatch repair during DNA replication. In this mechanism, the RecA protein recombines the corresponding on the undamaged parental strand of the same polarity 6. Double strand break repair; responsible for attaching two broken strands of DNA - uses homologous recombination repair and the corresponding region on the sister chromatid as a template
What term would be applied to a regulatory condition that occurs when protein greatly reduces transcription when associated with a particular section of DNA? 1. Negative control 2. Positive control 3. Inhibition 4. Activation 5. Stimulation
1. 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. 1. Negative inducible 2. Negative repressible 3. Positive inducible 4. Positive repressible
1. Negative inducible
Insulators can block the effects of enhancers only when 1. They lie between an enhancer and a promoter 2. They lie upstream of a promoter 3. They lie adjacent to a promoter 4. They lie within the structural genes 5. They lie within a consensus sequence
1. They lie between an enhancer and a promoter
Name two mutagens that would be classified as base analogs. 1. Acridine orange and proflavin 2. Ethylmethane sulfonate and ethylmethylketone peroxide 3. Ultraviolet light and cosmic radiation 4. 5-bromouracil and 2-aminopurine 5. Hydroxyurea and peroxidase
4. 5-bromouracil and 2-aminopurine
A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be the following. 1. Base analog 2. Transversion 3. Transition 4. Frameshift 5. Recombinant
4. Frameshift
_____ mutations produce new traits and are usually dominant. 1. Induced 2. Spontaneous 3. Forward 4. Gain of function 5. Lethal
4. Gain of function
The following may be caused by mobile genetic elements except ______. 1. Activate a gene in which they reside 2. Cause chromosome breaks 3. Disrupt a gene 4. Undergo mutation 5. All of the above
4. Undergo mutation
Conditional mutations are more likely to result from which of the following alterations to the coding region of a gene. 1. A mutation caused by a based addition or deletion 2. A mutation caused by a base addition 3. A mutation caused by X rays 4. A mutation caused by a deletion 5. A mutation caused by a tautomeric shift
5. A mutation caused by a tautomeric shift
E. coli bacteria are placed into a medium containing glucose and lactose. Which of the genes below do you expect to be turned on? 1. F-galactosidase 2. Lac I 3. Lac P 4. Permease 5. None of the above
5. None of the above
What is a mutation?
A change in the DNA sequence
Define polymorphism.
A gene or a trait is said to be polymorphic if there is more than one form of that trait in a population
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 links these disorders.
All 3 are caused by disparate genes, but each gene was found to contain repeats of a unique trinucleotide sequence. Additionally, the number of trinucleotide repeats may increase in each subsequent generation (genetic anticipation).
What is evolution? Describe four different mechanisms by which it can occur.
Answer: Evolution is a change in the allele frequencies in a population. It can occur via the following four mechanisms: a) Genetic drift. Conditions under which it occurs: Random change in allele frequencies due to small population size or a small founder population colonizing a new habitat. b) Migration/gene flow. Conditions under which it occurs: New individuals are added to a population. If their genetic makeup for any particular gene is different from that of the population they join, the overall allele frequency in the new population changes. c) Mutation. Conditions under which it occurs: A direct change in an allele as a result of some environmental insult and/or a problem in replication. d) Natural selection. Conditions under which it occurs: If there is variation for a trait, heritability for that trait, and differential reproductive success based on that trait, evolution by natural selection is occurring.
Assume that you wished to generate conditional 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?
B and C (only multi-option, no A and B or A and C)
Under the system of genetic control of the tryptophan operon,
B. When there is no tryptophan in the medium, transcription of the trp operon occurs at high levels
Because real-life populations are, of course, not infinitely large, why is the Hardy-Weinberg condition of an "infinitely large population" usually met for natural populations?
Because most natural populations are large enough that chance factors (i.e., sampling error, random genetic drift) have negligible effects on allele frequencies.
The bicoid gene of Drosophila generates embryos with two posterior regions. What aspect of embryonic development does the bicoid gene control?
Body segmentation, in this case, the posterior region
We discussed cis regulatory elements (CRMs) in transcriptional networks. What are CRMs and how are they involved in gene regulation?
CRMs are DNA sequences found within the introns and/or upstream or downstream of genes. They consist of a few hundred base pairs that contain binding sites for transcription factor proteins that are involved in activating (or repressing) transcription of the genes that they are located adjacent to.
Which of the following is NOT true regarding the differences in mRNA between prokaryotic cells and eukaryotic cells?
D. in eukaryotic cells, the transcription to mRNA and the translation from mRNA are coupled, while in prokaryotic cells transcription and translation are not
Which of these is a level or type of genetic regulation in eukaryotes?
DNA methylation, transcriptional, post-translational
_______ is the process whereby a cell's determined state is expressed
Differentiation
Define the term "fitness". What are three critical points to keep in mind when measuring fitness?
Fitness is the relative probability of survival and reproduction of a genotype or phenotype. Critical to assessing fitness is understanding that it is measured: a) relative to other genotypes/phenotypes in the population; b) in a specific environment; c) by reproductive success.
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 this, the energy requiring synthesis of B-galactosidase is needed. It is energy efficient to burn glucose rather than lactose
Describe the structure of a helix-turn-helix (HTH) motif. What is the general function of such motifs?
HTH motif were the first DNA-binding motifs identified. A geometric conformation is formed by two adjacent alpha helices separated by a "turn" of several amino acids. They bind to the major grooves of DNA and interact with the DNA backbone. Many HTH-containing proteins regulate gene expression.
What class of genes controls the developmental identity of segments along the anterior-posterior axis?
Homeotic genes
What are homeotic genes and what do they do?
Homeotic genes are important in development of higher level organism. They play an important role in segmentation of the body parts, They determine the fate and body part segmentation. Mutations in these genes can result in body parts on the wrong segment of the body.
From a human developmental standpoint, what is the significance of Hox genes?
Hox genes are essential genetic elements that aid in coordinating and regulating body plan for a developing embryo. Based on these genes, limb development and body part placement are determined. They are highly conserved among different organisms.
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 on to the next generation, it would be expressed. New recessive mutations are not normally passed on in the next generation, unless, through a combination with a like mutation from the other parents, they are homozygous.
The following table shows several bacterial strain lac operon genotypes (some are partial diploids). Fill in the blanks in the "lactose absent" and "lactose present" columns in this table. (+) means significant levels of active B-galactosidase enzyme can be detected. (-) means no significant levels of active B-galatosidase enzyme.
Lactose Absent: - + - + - - Lactose Present: + + - + + -
What is the difference between a missense mutation and 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.
One of the strongest lines of evidence that specialized cells of an adult carry all the genetic information for an entire adult organism comes from what types of experiments?
Nuclear transplantation experiments
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
Describe the function of promoters in eukaryotes. Where are they usually located, relative to the corresponding gene? What two sequence elements do they normally possess?
Promoter regions are necessary for the initiation of transcription. Promoters that interact with RNA pol II are usually located within 100 bp upstream of a gene and usually contain TATA box (-26 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.
Define RNA silencing (or interference). Explain how siRNAs arise and how they potentially affect gene expression. How are siRNAs different from the antisense RNA mechanisms?
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.
Describe alternative gene splicing. What is the result of the alternative splicing mechanism?
Same mRNA can be spliced in different way that yields different protein from same gene) The result of this is that cell can produce large number of protein than actual gene can encodes for)
How do segment polarity genes relate to pair-rule genes?
Segment polarity genes determine directionality and how a cell will differentiate. Pair rule genes determine the symmetry of segment polarity genes
What is the significance of the homeodomain?
The homeodomain is a highly conserved protein of sixty amino acids found in a variety of organisms, which, in conjunction with other factors (POU domains), are thought to play a role in DNA binding and transcriptional activation.
Which of the below is not true about the location of enhancers?
The position of the enhancer has no effect on gene regulation
What must be true for a population to be in Hardy-Weinberg equilibrium?
There must be random mating in the population; there must be an infinite population size; and there must be no evolution occurring (no natural selection, no genetic drift, no migration and no mutation).
Genetic regulation in eukaryotes can take place at a variety of levels from transcriptional to post-transcriptional. At what level is genetic regulation considered most likely in prokaryotes?
Transcriptional
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, the 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 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 factors TFIIA., and this structural motif has been identified in a variety of significant regulatory circumstances, including proto-oncogenes and developmental control genes in Drosophila.
Which of these are major structural classifications of DNA-binding domains that are found in eukaryotic transcription factors? a. zinc finger b. leucine zipper c. promoters d. helix-turn-helix e. coil-coil
a, b, d
One speaks of UAS (upstream activating sequences) as being DNase hypersensitive. We would interpret this to mean that: a. A UAS is constitutively open b. More than one strand of DNA exists in each UAS c. Each UAS is likely to be single-stranded d. Each UAS has more histone binding sites than non-UAS sites e. Any given UAS composed of a double-stranded site with a bound repressor
a. A UAS is constitutively open
A new kind of tulip is produced that develops only purple or pink flowers. Assume that flower color is controlled by a single-gene locus, and that the purple allele (C) is dominant to the pink allele (c). A random sample of 1000 tulips from a large cultivated field yields 847 purple flowers, and 153 pink flowers. a. Determine the frequency of the purple and pink alleles in this field population. b. Estimate the proportion of all purple flowering plants that are heterozygotes and homozygotes.
a. Assuming the population is in H-W equilibrium, let p = the dominant purple allele (C), and q = the recessive allele (c). Applying the H-W equation, the frequency of the pink allele = q^2 = 153/1000 = 0.153; and q = (0.153)^1/2 = 0.39. Because p + q = 1, p = 1 - q = 0.61. b. If the population is in H-W equilibrium, p^2 + 2pq + q^2 = 1. For the heterozygotes, 2pq = 2(0.61)(0.39) = 0.476. Therefore, 47.6%, or (0.476)(1000) = 476 of all the purple flowered plants in this population are expected to be heterozygotes (Cc), and consequently, (p^2)(1000) = (0.61)^2 (1000) = 371 plants are expected to be
Regarding eukaryotic and prokaryotic genetic regulation, what process seems to be the most similar between the two? a. Transcriptional regulation b. RNA splicing regulation c. intron/exon shuffling d. 5'-cap regulation e. ploy(A)tail addition
a. Transcriptional regulation
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 a. Xeroderma pigmentosum b. SCID c. Phenylketonuria d. Muscular dystrophy e. Huntington disease
a. Xeroderma pigmentosum
Channels between chromosomes in the interphase nucleus are called a. interchromosomal compartments. b. localized zones. c. nonlocalized zones. d. extrachromosomal elements. e. subchromosomal territories.
a. interchromosomal compartments.
An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operson. The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule. a. negative repressible b. positive inducible c. positive repressible d. negative inducible
a. negative repressible
Regulation of gene expression using siRNAs is found in a. Prokaryotes only b. Eukaryotes only c. Prokaryotes and eukaryotes
b. Eukaryotes only
What is the function of cAMP in regulation of the lac operon? a. It activates a repressor protein b. It activates an activator protein c. It inactivates a repressor protein d. It inactivates an activator protein
b. It activates an activator protein
Which of the following is TRUE for both prokaryotic and eukaryotic gene expression? a. After transcription, a 3' poly-A tail and a 5' cap are added to mRNA b. RNA polymerase binds to the promoter region to begin transcription c. mRNA is synthesized in the 3'--> 5' direction d. The mRNA is the exact compliment of the gene from which it was copied
b. RNA polymerase binds to the promoter region to begin transcription
considering the location of genes in the interphase nucleus, certain chromosomal territories appear to exist, specifically, a. even-numbered chromosomes are located in the interior of the nucleus, whereas odd-numbered chromosomes are located peripherally. b. each chromosome appears to occupy a discrete domain. c. large chromosomes are more likely to be located in the center of the nucleus. d. small chromosomes are more likely to be located in the center of the nucleus. e. gene-poor regions of chromosomes are located outside the nucleus, whereas gene-rich regions are located inside the nucleus.
b. each chromosome appears to occupy a discrete domain.
A mutant E. coli strain, grown under conditions that normally induce the lac operon, produces high amounts of B-galactosidase. What is a possible genotype of the cells? a. lacI+, lacP+, lacO+, lacZ-, LacY+, lacA+ b. lacI+, lacP+, lacOc, lacZ+, lacY+, lacA+ c. lacI-, lacP+, lacO+, lacZ-, lacY+, lacA+ d. lacI+, lacP-, lacO+, lacZ+, lacY+, lacA+
b. lacI+, lacP+, lacOc, lacZ+, lacY+, lacA+
It is estimated that transposable elements compose approximately what percent of the human genome? a. <1 b. 10 c. 50 d. 1 e. 99
c. 50
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? a. 5-bromouracil b. 2-amino purine c. Acridine orange d. Ethylmethane sulfonate
c. Acridine orange
LINES differ from retrotransposons in that LINES: a. Do not encode transposase b. Do not encode reverse transcriptase c. Do not contain LTRs d. Do not transpose in a replicative manner e. Do not contain the transposase gene
c. Do not contain LTRs
Two modular elements that appear as consensus sequences upstream from RNA polymerase II transcription start sites are a. microsatelites and transposons b. rDNA and nucleolar organizers c. TATA and CAAT d. TTAA and CCTT e. Enhancers and telomeres
c. TATA and CAAT
It is possible for a repressor to negatively regulate the expression of an operon because a. The repressor induces the expression of inducer b. One of the genes expressed in the operon negatively regulates the repressor c. The repressor binding site overlaps the promoter site of the operon allowing it to physically block binding of RNA polymerase d. The repressor binding site on the DNA overlaps with the translation start site
c. The repressor binding site overlaps the promoter site of the operon allowing it to physically block binding of RNA polymerase
This question relates to the regulation of enzymes involved in the synthesis of tryptophan in E. coli. If tryptophan is present in the medium and available to the bacterium, a. The repressor is inactive and the tryptophan operon is "off" b. The repressor is inactive and the tryptophan operon is "on" c. The repressor is bound to the operator, thus blocking transcription d. The five structural genes associated with tryptophan synthesis are being transcribed at "induced" levels e. Positive control is occurring
c. The repressor is bound to the operator, thus blocking transcription
What modification neutralizes the charges of histones that promote ionic interaction with DNA? a. polyadenylation b. demethylation c. acetylation d. phosphorylation
c. acetylation
The lac repressor binds to a. RNA polymerase. b. promoter and lactose. c. lactose and DNA. d. d-galactosidase, permease and transacetylase. e. RNA polymerase and DNA.
c. lactose and DNA.
What term refers to a contiguous genetic complex that is under coordinate control? a. prototroph b. attenuation c. operon d. lysogen e. allosteric
c. operon
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. a. Complete metamorphic systems b. Incomplete metamorphic systems c. Epigenetic developmental systems d. Strains with specific mutations e. Museum specimens
d. Strains with specific mutations
siRNAs and miRNAs are produced by: a. The cleavage of RISCs by endonucleases b. The cleavage of functional mRNA within the cytoplasm c. The cleavage of pre-mRNA in the nucleus d. The cutting and processing of double-stranded RNA by DICER enzymes e. The cutting and processing of double-stranded RNA by Slicer enzymes
d. The cutting and processing of double-stranded RNA by DICER enzymes
In what way do upstream activator sequences (UASs) regulatory sequences in yeast, differ from enhancers and silencers? a. Enhancers only function downstream. b. UASs can only function in the 5'-3' direction. c. UASs function in the middle of transcription units. d. UASs only function upstfream. e. UASs only function downstream.
d. UASs only function upstfream.
A mutant E. coli strain, grown under conditions that normally induce the lac operon, does not produce B-galactosidase. What is a possible genotype of the cells? a. lacI+, lacP+, lacO+, lacZ-, LacY+, lacA+ b. lacI+, lacP+, lacOc, lacZ+, lacY+, lacA+ c. lacI-, lacP+, lacO+, lacZ-, lacY+, lacA+ d. lacI+, lacP-, lacO+, lacZ+, lacY+, lacA+
d. lacI+, lacP-, lacO+, lacZ+, lacY+, lacA+
in the lactose operon, the product of structural gene lacZ is capable of a. Nonautonomous replication b. Forming lactose from two glucose molecules c. Replacing hexokinase in the early steps of glycolysis d. splitting the β-linkage of lactose
d. splitting the β-linkage of lactose
centromere carried out in a variety of organism indicate that the n e is not necessarily fixed. What centromere support this indication?
drosophila experiment with the eyeless gene; xenopus experiment
Which of the following clusters of terms applies when addressing enhancers or silencers as elements associated with eukaryotic genetic regulation? a. cis-acting, variable position, fixed orientation b. cis-acting, fixed position, fixed orientation c. trans- and cis-acting, variable position d. trans-acting, fixed position, fixed orientation e. cis-acting, variable orientation, variable position
e. cis-acting, variable orientation, variable position
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. a. dominant; recessive; semidominant b. recessive; dominant; codominant c. restrictive; permissive; dominant d. permissive; restrictive; dominant e. permissive; restrictive; lethal
e. permissive; restrictive; lethal
Riboswitches were first discovered in 2002 and have been found in... a. Plants b. Bacteria c. Fungi d. Archaea e. In none of the listed organisms f. In all of the listed organisms
f. In all of the listed organisms
Give a brief definition of homeobox.
homeobox consists of 180bp and a domain of 60 amino acids (homeodomain). The homeobox essentially encodes the information that directs the development and placement of an organism's body segments.
Mutations in the selector genes sometimes form structures in the wrong segment, transforming the antenna of a fly into a leg, for example.What term is given to such mutations?
homeotic mutation
Individuals with the same genetic background and a high degree of homozygosity are said to be isogenic. Of what value are isogenic strains in genetic studies?
in an isogenic strain, all individuals are genetically identical. With this, geneticists around the world can work on genetically identical individuals
Which of the following are general categories of mutations? a. lethal b. DNA c. conditional d. protein e. behavioral
lethal, conditional, behavioral
In Drosophila, _____ genes are influential in determining the anterior-posterior organization of the developing embryo.
maternal effect
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 an organism's genome. They are further processed after transcription by Dicer protein into small dsRNA molecules. These small ds molecules are targeted into RISC proteins where they are unwound into single stranded RNAs. These ss RNAs are then able to inhibit translation from mRNAs in a number of ways including inhibition of translation, targeting mRNAs for degradation, transcriptional silencing, or sequestration of mRNAs
Which of the following terms best characterizes catabolite repression associated with the lactose operon in E. coli?
positive control
Describe the relationship between the maternal-effect gene bicoid and the zygotic gene hunchback.
the maternal-effect gene bicoid effects the hunchback gene during development of the embryo. The bicoid gene influences the phenotype to look more maternal, even if the genotype is different
Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are called
transversions and transitions.
