Concept explainers
A temperature-sensitive allele of the gene encoding the Notch protein (Nts) helped researchers understand the many roles of this protein in fly eye development. Notch is a transmembrane receptor that, when bound to a ligand, relays a signal to the nucleus. In one experiment, wild-type and Nts homozygous developing eyes were allowed to grow in larvae for several hours at permissive temperature, and then the temperature was shifted to the restrictive temperature. After 4 hours, the eyes were dissected from the larvae and the photoreceptors were labeled with an antibody to a protein expressed in all photoreceptors (blue cells in the figure that follows are labeled with antibody). The black dots represent ommatidia at more advanced stages of development that are not shown in the figure.
Eye development occurs in a structure called the eye imaginal disc present in the larva.
Ommatidia develop behind an indentation called the morphogenetic furrow (mf in the diagram). The furrow forms at the posterior of the disc and moves anteriorly; every 2 hours, a new row of ommatidia initiates development posterior to the furrow, while the rows behind that row mature successively to the next stages of assembly. (Only one ommatidium is shown in the diagram, rather than an entire row.) Therefore, in a single eye disc, ommatidia at all stages of development are present. As you saw in Fig. 19.3, the first cells to join the ommatidium are the photoreceptors, R1–R8, and they do so in a particular order.
Describe the different roles of the Notch protein at different stages of ommatidial assembly.
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Genetics: From Genes to Genomes
- ) Explain how and why dorsal/ventral polarity will be affected in fly Question 3 (1. embryos carrying the following mutations; also in each case darken in the area of the cells in the cross-sectional view of the fly embryo which are expected to express the paulie gene. D = dorsal; V = ventral. a) a mutation which results in the deletion of the cytoplasmic domain of the Cookie protein. b) A mutation which results in a constitutively active Bombe protein, i.e. the Bombe protein is always in an activated state. c) A mutation which causes the Pickle protein to be retained in the cytoplasm of the embryo.arrow_forwardIn the experiment below, mice were treated with a virus that inhibited expression of angiopoietin 2, MMP3 and MMP10 in the lung or with a control virus (Mock). Breast cancer cells that express the gene luciferase were then injected into the mammary glands of the mice. The metstasis of the tumors to the lungs could then be measured by imaging the presence of luciferase in the lungs. In 5-6 sentences, explain the data below and why knockout of Angpt2, MMP3 and MMP10 appears to inhibit metstastasis.arrow_forwardYou isolate a glp-1 mutation of C. elegans and discoverthat the DNA region encoding the spatial control region(SCR) has been deleted. What will the GLP-1 protein expression pattern be in a four-cell embryo in mutant heterozygotes? In mutant homozygotes?arrow_forward
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- Following a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Which is the genotype of the rhythmic flies resulting from the testcross? Select only one answer 1. C/C d/d 2. C/c D/d 3. C/c d/d 4. c/c…arrow_forwardFollowing a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call C and d. The two homozygous C/C and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/C and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for C and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Using the number of flies expected for the Parental and the Recombinant genotypes and the formula that defines recombination frequency, what is the distance between loci C…arrow_forwardFollowing a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Using the number of flies expected for the Parental and the Recombinant genotypes and the formula that defines recombination frequency, what is the recombination…arrow_forward
- Following a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Comparing the number of flies expected for the Parental and the Recombinant genotypes, what can be concluded about the C and D loci? Select only one answer. 1. The…arrow_forwardFollowing a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. What is the genotype of the F1 (progeny of Females 3 x Males 4). Select only one answer. 1. C/c D/d 2. C/C d/d 3. C/C D/D 4. c/c D/d…arrow_forwardFollowing a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. What is the genotype of Males 4? Select only one answer. 01. C/C D/D O 2. C/C D/d O3. C/C d/d O 4. C/C D/D O 5. c/c D/d O 6. C/cd/d 07. c/c D/D O 8. C/C D/d O 9. c/cd/d Karrow_forward
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