Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 19, Problem 32P
In flies developing from eggs laid by a nanos-mother, development of the abdomen is inhibited. Flies developing from eggs that have no maternally supplied hunchback mRNA are normal. Flies developing frog eggs laid by a nanos-mother that also have no maternally supplied hunchback mRNA are normal. If too much Hunchback protein accumulates in the posterior of the egg, abdominal development is prevented.
| a. | What do these findings say about the function of the Nanos protein and of the hunchback maternally supplied mRNA? |
| b. | What do these findings say about the efficiency of biological processes that are subject to evolution? |
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a. The eyeless gene is required for eye formation in Drosophila. It encodes a homeodomain. What would you predict about the biochemical function of the Eyeless protein?b. Where would you predict that the eyeless gene is expressed in development? How would you test your prediction? c. The Small eye and Aniridia genes of mice and humans, respectively, encode proteins with very strong sequence similarity to the fly Eyeless protein, and they are named for their effects on eye development. Devise one test to examine whether the mouse and human genes are functionally equivalent to the fly eyeless gene.
Protein levels and mRNA levels for a particualr gene don’t always match. For example, the GCN4 gene in yeast is always producing mRNA, but the Gcn4 protein is only made when the cells are starved.
A. what is one mechanism by which changes in mRNA levels are not always matched by changes in the protein product of that mRNA?
As we have learned in this chapter, the Nanos protein inhibits the translation of hunchback mRNA, lowering the concentration of Hunchback protein at the posterior end of a fruit-fly embryo and stimulating the differentiation of posterior characteristics. The results of experiments have demonstrated that the action of Nanos on hunchback mRNA depends on the presence of an 11-base sequence that is located in the 3′ untranslated region (3′ UTR) of hunchback mRNA. This sequence has been termed the Nanos response element (NRE). There are two copies of NRE in the 3′ UTR of hunchback mRNA. If a copy of NRE is added to the 3′ UTR of another mRNA produced by a different gene, that mRNA is repressed by Nanos. The repression is greater if several NREs are added. On the basis of these observations, propose a mechanism for how Nanos inhibits Hunchback translation.
Chapter 19 Solutions
Genetics: From Genes to Genomes
Ch. 19 - Match each of the terms in the left column to the...Ch. 19 - a. If you were interested in the role of a...Ch. 19 - Early C. elegans embryos display mosaic...Ch. 19 - Hypomorphic mutations in the wingless gene of...Ch. 19 - Prob. 5PCh. 19 - In 1932, H. J. Muller suggested a genetic test to...Ch. 19 - a. Explain how you could use worms transformed...Ch. 19 - Suppose you want to determine whether a particular...Ch. 19 - Sevenless is an unusual receptor protein in that...Ch. 19 - Suppose that you generated flies containing a...
Ch. 19 - Drosophila researchers have collected many strains...Ch. 19 - As an alternative to random mutagenesis,...Ch. 19 - A C. elegans nematode gene called par-1 helps to...Ch. 19 - The molecular identity of the fruit fly rugose...Ch. 19 - To determine the focus of action of boss,...Ch. 19 - Suppose a particular gene is required for early...Ch. 19 - Researchers have exploited Minute mutations in...Ch. 19 - Some ts alleles are temperature sensitive during...Ch. 19 - The following figure shows the temperature-shift...Ch. 19 - A temperature-sensitive allele of the gene...Ch. 19 - Hypomorphic alleles of a pleiotropic gene...Ch. 19 - In addition to the maternal effect genes that...Ch. 19 - The yan gene encodes a transcription factor that...Ch. 19 - Recall from Chapter 17 that in Drosophila, sex...Ch. 19 - a. Explain the difference between maternal...Ch. 19 - In the 1920s, Arthur Boycott, working with the...Ch. 19 - The Drosophila mutant screen shown on the...Ch. 19 - Some genes are required both zygotically and...Ch. 19 - How would a human with a mutation in a maternal...Ch. 19 - One important demonstration that Bicoid is an...Ch. 19 - The hunchback gene contains a 5 transcriptional...Ch. 19 - In flies developing from eggs laid by a...Ch. 19 - Wild-type embryos and mutant embryos lacking the...Ch. 19 - The Drosophila even-skipped eve gene has four...Ch. 19 - In Drosophila with loss-of-function mutations...Ch. 19 - It is crucial to the development of Drosophila...Ch. 19 - In the plant Arabidopsis thaliana, every flower is...
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- What would be the most likely effect of inhibiting the translation of hunchback mRNA throughout a Drosophila embryo?arrow_forwardIn flies, the gap gene kruppel is expressed in a broad band in the middle of the embryo with giant expressed as its anterior border and knirps at its posterior border. How is the expression of kruppel limited to this band in the embryo? Describe the spatial regulation of the kruppel gene.arrow_forwardA Drosophila egg that is bed lbcd may develop normally, but the adult fruit fly will not be able to produce viable offspring. How is this possible? The mother can provide the bcd mRNA required for normal development, but the adult bcd /bcd female fly cannot make its own bcd mRNA. The Hox genes in the egg play a redundant role to bcd during development in a bcd / bcd egg, but reproduction requires bcd. Drosophila sperm contains the functional bcd gene product required for normal development, but the adult sex cells will not be able to produce the functional product. The nanos gene product functionally compensates for lack of bcd expression in the developing fly but not in its offspring.arrow_forward
- In the sea urchin, early development may occur even in the presence of actinomycin D, which inhibits RNA synthesis. However, if actinomycin D is present early in development but is removed a few hours later, all development stops. In fact, if actinomycin D is present only between the sixth and eleventh hours of development, events that normally occur at the fifteenth hour are arrested. What conclusions can be drawn concerning the role of gene transcription between hours 6 and 15?arrow_forwardWhich of the following applies to the female sex determination in Drosophila melanogaster fruit flies? (Mark all that apply) When the X:A ratio is 1.0, the SXL gene is transcribed during the early embryonic stages. The SXL protein inhibits the expression of female differentiaion genes The SXL protein promotes the correct splicing of the Tra pre-mRNA so that functional Tra protein is made. The presence of the SXL protein promotes the correct splicing of the SXL pre-mRNA during later embryonic stages to ensure to continuous production of SXL protein. The Tra protein will stimulate the expression of male-specific genes.arrow_forwardDiscuss the morphological differences between the parasegments and segments of Drosophila. Discuss the evidence, providing specific examples, that suggests the parasegments of the embryo are the subdivisions for the organization of gene expression.arrow_forward
- Describe the appearance of a Drosophila embryo, in which the knirps gene protein-coding sequence has been replaced by lacZ, following incubation in a solution of X-gal.arrow_forwardSuppose expression of gene A is limited to the middle part of the early mouse embryo. Expression of gene B is located on the posterior and anterior ends of the early mouse embryo, but not in the middle. When gene B is mutated, expression of gene A is distributed over the whole embryo. What is a likely explanation for this data? a) Gene A acts as an activator of gene B. Ob) Gene A acts as a repressor of gene B. O c) Gene B acts as an activator of gene A. () d) Gene B acts as a repressor of gene A.arrow_forwardGive typing answer with explanation and conclusionarrow_forward
- MyoD is a transcriptional activator that turns on theexpression of several muscle-specific genes in humancells. The Id gene product inhibits MyoD action.a. One possibility is that the Id protein directly represses the expression of these muscle-specificgenes. Explain how Id would function if it were arepressor.b. Another possibility is that Id inhibits musclespecific gene transcription indirectly, by preventingMyoD function. Explain how Id could function asan indirect repressor.c. Suppose you know the amino acid sequence ofthe Id protein. How might this information supportthe hypothesis in part (a) or in part (b)?arrow_forwardWhat is cell differentiation? Discuss the role of myogenic bHLH proteins in the differentiation of muscle cells. Explain how they work at the molecular level. In your answer, explain how protein dimerization is key to gene regulation.arrow_forwardAnother way to study the role of proteins (e.g., transcription factors) that function in development is to microinject the mRNA that encodes a protein, or the purified protein itself, into an oocyte or embryo, and then determine how this affects the subsequent development of the embryo, larva, and adult. For example, if Bicoid protein is injected into the posterior region of an oocyte, the resulting embryo will develop into a larva that has anterior structures at both ends. Based on your understanding of the function of each developmental gene, what would be the predicted phenotype if the following proteins or mRNAs were injected into normal oocytes? A. Nanos mRNA injected into the anterior end of an oocyte B. Antp protein injected into the posterior end of an embryo C. Toll mRNA injected into the dorsal side of an early embryoarrow_forward
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