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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- 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_forwardWhat is the difference between a maternal-effect gene and a zygotic gene? Of the following genes that play a role in Drosophila development, which are maternal-effect genes and which are zygotic? Explain your answer. A. nanos B. Antp C. bicoid D. labarrow_forwardName 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_forward
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- You 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_forward12. 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_forwardDrosophila females homozygous for loss-of-functionmutations in the gene aubergine are sterile. RNA-Seqexperiments show that in the ovaries of these females,the levels of RNAs for many kinds of transposable elements are more than 10× higher than in wild-type ovaries. The aubergine gene encodes a Piwi-family protein.a. Why do you think these females are sterile?b. Piwi proteins interact with piRNAs that are transcribed from piRNA gene clusters. Given that thelevels of many kinds of TEs are elevated in mutantovaries, what kinds of DNA sequences do youthink are located in these clusters?c. Many investigators think of piRNAs as a kind ofdefensive mechanism that protects organisms fromthe effects of new transposable elements that mightbe introduced into genomes, for example fromother species. Explainarrow_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. 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_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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