"Head to rump and in between" (1.5 pts.) In Drosophila, it is well established that nanos is involved in specifying the

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Head To Rump And In Between 1 5 Pts In Drosophila It Is Well Established That Nanos Is Involved In Specifying The 1 (58.04 KiB) Viewed 69 times

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"Head to rump and in between" (1.5 pts.) In Drosophila, it is well established that nanos is involved in specifying the anterior-posterior axis determination. Predict the effect on the embryo if... a. Wild-type NANOS mRNA is injected into the center section of the egg exactly equidistant from the posterior and anterior ends. . Now thinking about what bicoid and nanos do in the embryo, let's add in a few more genes: caudal and hunchback. Both are expressed at the RNA level throughout the embryo, but the proteins are largely restricted (hunchback is abundant in the anterior, while caudal is abundant in the posterior). Concentration • This restriction is due to the fact that bicoid protein binds to the caudal promoter and blocks protein production. Also, nanos protein stops hunchback RNA from being made into protein by destroying the poly-A tail. (A) Oocyte mRNAs Anterior -bicoid mRNA Concentration Anterior -Bicoid (B) Early cleavage embryo proteins Anterior hunchback mRNA caudal mRNA nanos mRNA Hunchback Caudal- Posterior Nanos Posterior (C) ANTERIOR bicoid mRNA Posterior Cortex, Grauzone. Staufen Bicoid protein- POSTERIOR anos mRNA Oskar Nanos protein caudal mRNA Caudal protein Pumilio p55 hunchback mRNA Hunchback protein
b. What would happen to hunchback RNA and hunchback protein in a bicoid mutant (lacking bicoid protein)? You can phrase your answer as a graph as above or as an embryo drawing. c. The gap gene Kruppel mRNA is expressed in the middle of the embryo where hunchback and caudal protein are at their lowest. Draw the expression pattern (like you did in (b)) of Kruppel in a wild-type and bicoid mutant. Hint: If hunchback and caudal are lowest in the middle where Kruppel is, what does that tell you about how these two proteins might regulate Kruppel (positively or negatively)? You might think this is an incredibly over-the-top level of detail for this area but in reality, we have barely scratched the surface. Consider that we only focused in on anterior-posterior axes. We have not even mentioned dorsal-ventral axes. There's also tissue and organ development! There are a whole different set of genes with different mechanisms to specify these regions of the fly embryo. Results of mutagenesis screens Total lines established and tested 26978 18136 4332 580 Mutations causing embryonic lethality Mutations causing embryonic phenotypes Complementation Groups (Genes) 139 The project that yielded this data was amazing. Even if you looked at 1 fruit fly from each line for 5 seconds, it would take you 37 hours to look at every one them (they obviously spent longer than 5 seconds). There is a famous rumor that while this research was being done, anytime an undergraduate or passer-by took a peek into the lab, they would be conscripted to look at embryos to support the research. Both researchers are alive today (as of 2022) and have switched their focus somewhat with Nusslein Volhard now a zebrafish developmental biologist (she did the same experiments in zebrafish and looked at 1200 unique lines). Volhard was called "decidedly lazy" by her high school teachers. Their work on Drosophila won them the Nobel Prize in Medicine in 1995. Out of 224 winners for the Nobel in Medicine, only 12 were women.