The Hoxd
a. What would be the consequence of ectopically expressing Hoxd
b. You wish to examine the effect of loss
Figure 18.18
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Genetic Analysis: An Integrated Approach (3rd Edition)
- a) Do the loss of function phenotypes differ between the genes between the genes in figure 1? What does this mean? b) What are the two cell types responsible for producing maternal gene products involved in terminal patterning in the Drosophila cocyte? In which of these two cell types is each of the three genes expressed? c) Based on the phenotypes you observed for the three genes, and on the differences in their expression patterns, which one of the genes do you think is the localised determinant of terminal patterning? d❘ From the gain-of-function experiments, do trunk and torso like work upstream or downstream of torso? Explain. (4 m e) How might you test which of the trunk and torso-like genes acts upstream of the other? f) The torso gene has been shown to have another important role in Drosophila development outside of terminal patterning. What do you think would be a good first experiment to do to begin to investigate possible other roles for the trunk or torso - like genes? C a…arrow_forwardIn flies developing from eggs laid by a nanos−mother, development of the abdomen is inhibited.Flies developing from eggs that have no maternallysupplied hunchback mRNA are normal. Flies developing from eggs laid by a nanos− mother that alsohave no maternally supplied hunchback mRNA arenormal. If too much Hunchback protein accumulatesin the posterior of the egg, abdominal developmentis prevented.a. What do these findings say about the function ofthe Nanos protein and of the hunchback maternallysupplied mRNA?b. What do these findings say about the efficiency ofbiological processes that are subject to evolution?arrow_forwarda) What is the role of the Hox genes in animal development and what types of phenotypes do you see in mutations of Hox genes? Provide an example of a mutant phenotype of a Hox gene in Drosophila. 3mrks The Hox genes are known to act in combination. Panel A in figure below shows the normal expression patterns of the bithorax complex, and segments that align with the expression patterns. Panel B shows the segmental phenotypes in mutants for both abdominal - A and Abdominal - B, panel C shows the phenotypes in mutants for Abdominal - B, and panel D shows the phenotypes in mutants for Ultrabithorax. b) Describe how the segmental phenotypes illustrate the combinatorial action of Hox genes (you can ignore A9 as it is patterned by the terminal patterning system). 4mrks A) Parasegments 11 12 13 14 B) D) 10 11 12 13 14 Segments A2 A3 A4 A5 Abdominal-B abdominal-A Ultrabithorax T1 12 13 A1 11 12 12 12 A2 A3 A4 Aarrow_forward
- Flies homozygous for recessive null mutations in thesevenless (sev) or bride-of-sevenless (boss) genes have the same mutant phenotype: Every ommatidium(facet) in their eyes lacks photoreceptor cell 7 (R7).The R7 cells enable flies to detect UV light.a. Given that flies normally move toward light, suggest a screening method that would enable you toidentify mutations in additional genes required forR7 determination.b. Would you be able to recover mutations in everygene required for R7 development with yourmethod? Explain.c. How could you tell whether any of the new mutationsyou found in your screen are alleles of sev or boss?d. Suppose you found one recessive mutant allele ofa gene not previously known to be involved in eyedevelopment. How could you use this allele in anew mutagenesis screen to find additional allelesof this gene? Why might you want additional mutant alleles to study the process?arrow_forwardThe Drosophila gene Sex lethal (Sxl) is deserving of itsname. Certain alleles have no effect on XY animals butcause XX animals to die early in development. Other alleles have no effect on XX animals but cause XY animals to die early in development. Thus, some Sxl allelesare lethal to females, while others are lethal to males.a. Would you expect a null mutation in Sxl to causelethality in males or in females? b. Why do Sxl alleles of either type cause lethality ina specific sex?The gene transformer (tra) gets its name from sexualtransformation, as some tra alleles can change XXanimals into morphological males, while other traalleles can change XY animals into morphologicalfemales.c. Which of these sex transformations would becaused by null alleles of tra and which would becaused by constitutively active alleles of tra?d. In contrast with Sxl, null tra mutations do notcause lethality either in XX or in XY animals.However, the Sxl protein regulates the productionof the Tra protein. Why…arrow_forwardYou are interested in studying position effect variegation in Drosophila using the chromosome depicted below: Deactivation of the w+ gene gives a white eye phenotype and deactivation of the rst+ gene gives a rough eye phenotype; the normal phenotypes are red and smooth. Because the rst+ and w+ genes have now been placed close to a heterochromatic domain, some sections (or sectors) of the eye display mutant phenotypes due to gene deactivation while others display the normal, wild type phenotype. Which phenotype would you not expect to see rst w Inverted X chromosome white smooth eye sectors white rough eye sectors red smooth eye sectors red rough eye sectorsarrow_forward
- Name three possible factors contributing to early asymmetries in a developing embryo (i.e. what are the kinds of things early on that lead to the development of the body axes - dn, a/p, l/r, etc)? In the fruit fly drosophila melanogaster, the anterior-to-posterior body axis becomes segmented into distinct regions. explain the role of the genes bicoid and nanos in this process.arrow_forwardHere are schematic diagrams of mutant Drosophila larvae. The left side of each pair shows a wild-type larva, with gray boxes showing the sections that are missing in the mutant larva. Which type of gene is defective in each larva: a gap gene, a pair-rule gene, or a segment-polarity gene?arrow_forward) 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_forward
- 12. a. You want to create a genetic construct that will express GFP in Drosophila. In addition to the GFPcoding sequence, what DNA element(s) must youinclude in order to express this protein in flies if theconstruct were integrated into the Drosophila genome? Where should such DNA element(s) be located? How would you ensure that GFP is expressedonly in certain tissues of the fly, such as the wing?b. Suppose you insert the GFP coding region plus allof the DNA elements required by the answer to part(a)—except the enhancer—between inverted repeatsfound at the ends of a particular transposable element.Because all of the DNA sequences located betweenthese inverted repeats can move from place to placein the Drosophila genome, you can generate manydifferent fly strains, each with the construct integrated at a different genomic location. You now examine animals from each strain for GFPfluorescence. Animals from different strains showdifferent patterns: some glow green in the eyes,others in…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 lestcross 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. Considering that out of 1000 flies resulting from the Testcross only 125 are rhythmic how many flies in total are approximatively expected for the Parental genotypes?…arrow_forward
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