The paired-like homeodomain transcription factor 1 (pitxl) is expressed in the hindlimbs of developing mouse embryos, and its homologue is expressed in the pelvic region of the nine-spine stickleback fish (Pungitius pungitius). You are beginning a research project on pitxl and your supervisor is convinced that pitxl has been co-opted to make armor around the pelvic region of this species of stickleback. You begin by isolating RNA from a freshwater Pungitius pungitius that has very reduced armor. You convert the RNA to cDNA and amplify the pitxl cDNA using PCR. You have your pitxl PCR product sequenced and find it has exactly the same sequence as the marine Pungitius pungitius with armor. In light of this evidence, analyze your supervisor's hypothesis.
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BIOLOGY VOL. II
- 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.arrow_forwardYou wish to find the cis-acting regulatory DNA elements responsible for the transcriptional responses of two genes, c-fos and globin. Transcription of the c-fos gene is activated in response to fibroblast growth factor (FGF), but it is inhibited by cortisol (Cort). On the other hand, transcription of the globin gene is not affected by either FGF or cortisol, but it is stimulated by the hormone erythropoietin (EP). To find the cis-acting regulatory DNA elements responsible for these transcriptional responses, you use the following clones of the c-fos and globin genes, as well as two “hybrid” combinations (fusion genes), as shown in the diagram below. The letter A represents the intact c-fos gene, D represents the intact globin gene, and B and C represent the c-fos–globin gene fusions. The c-fos and globin exons (E) and introns (I) are numbered. For example, E3(f) is the third exon of the c-fos gene and I2(g) is the second intron of the globin gene. (These labels are provided to help you…arrow_forwardA pharmaceutical researcher performs preclinical testing on a novel chemotherapeutic drug. When rat embryos are exposed to this drug during an early stage of organogenesis, they develop severe skeletal malformations. Further genetic analysis reveals that the drug causes mutations in numerous homeobox genes containing highly conserved 180 base pair DNA sequences. The genes affected by this drug most likely code for which of the following proteins?arrow_forward
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- 1) Are NGN2-induced neurons (NGN2-iNs) the same as the cells in neural organoids? If not, how are they different? 2) Forced expression of the transcription factor neurogenin 2 (NGN2) induces human neurons, but to mature into electrophysiologically active neurons the require the presence of another cell type: what is that? 3)What kind of expression of NGN2 is associated with a central nervous system (CNS)-like cell? How do you know this?arrow_forwardThe transcription factor Pax6 is required continually during the life of a mouse (or a human) for the development of the retina. Homozygous Pax6 knockout mice die soon after birth because Pax6 protein is also required in essential organs, such as the pancreas. a) In order to study the role of Pax6 in eye development a researcher wants to generate a mouse that expresses Pax6 everywhere except in its eyes. Describe how you could construct such a mouse by floxing the gene. Is it possible to achieve the same end with a transgene? (Hint: think about using cDNA and RNAI) b) Suppose you want to create a mouse similar to that in part (a), but one where the eye cells from Pax6 function has been removed and now express a gene that specifies a green fluorescent protein (GFP). Marking the cells in this way will allow the investigators to see the shapes of the Pax6- eye cells more easily than if they did not express GFP. Diagram a Pax6 gene construct that would enable the researcher to do this…arrow_forwardMany currently marketed drugs exert their pharmacological effects by binding to ligand-activated transcription factors and modulating gene expression. One example, are various drugs that target the estrogen receptor to treat breast cancer, osteoporosis and post-menopausal symptoms. Below is a ChIP experiment examining the effects of no drug treatment (C), the natural hormone estrogen (E) and the drugs tamoxifen (T) and raloxifene (R) on recruitment of coactivators (SRC-1 and CBP), Histone Deacetylase Complexes (HDACs) and acetylation of histones associated with the C-myc gene. Which of the following statements are correct based on this data (select all that apply)?arrow_forward
- Now read this abstract from a 2013 journal article What is the authors' explanation of how Gal80p works? Note UASG from the question above is the same as UASGAL The DNA-binding transcriptional activator Gal4 and its regulators Gal80 and Gal3 constitute a galactose-responsive switch for the GAL genes of Saccharomyces cerevisiae. Gal4 binds to GAL gene UASGAL. (upstream activation sequence in GAL gene pro- moter) sites as a dimer via its N-terminal domain and activates transcription via a C-terminal transcription activation domain (AD). In the absence of galactose, a Gal80 dimer binds to a dimer of Gal4, masking the Gal4AD. Galactose triggers Gal3-Gal80 interaction to rapidly initiate Gal4-mediated transcription activation. Just how Gal3 alters Gal80 to relieve Gals0 inhibition of Gal4 has been unknown, but previous analyses of Gal80 mutants suggested a possible competition between Gal3-Gal80 and Gal80 self-association interactions. Here we assayed Gal80-Gal80 interactions and tested for…arrow_forwardTermicin is a small antifungal protein in termites that is produced by cells and secreted into termite saliva in response to a pathogen. In vitro translation of the termicin-encoding gene is performed, and the effects of that product are compared to those of termicin extracted from a termite. You see that extracted termicin exhibits more antifungal behavior than in vitro translated termicin. After further analysis, you see that extracted termicin contains 3 disulfide bonds, while in vitro translated termicin contains zero. The addition of microsomes to the in vitro translation reaction results in termicin with all 3 disulfide bonds. What experimental condition is most likely responsible for this difference? A. in vitro translation was not performed at the correct temperature affecting protein folding B. a mutation occurred during in vitro translation, leading to differences in disulfide bond formation O C. the UPR can not be activated in vitro, therefore, this protein can only be…arrow_forwardProgesterone is a steroid hormone (also described as a ligand) that prepares the body for pregnancy. It binds to the progesterone receptor (PR) protein in the cytoplasm of various cells. Ligand bound PR acts as a transcriptional activator, binds to the DNA in the promoter region of several genes and leads to transcriptional activation of these genes. Ligand bound PR has been shown to increase the expression of a gene, FKBP5. You are studying the activity of wild-type (WT) and mutant PR in cells by examining expression of FKBP5. Results are obtained as shown in the figure below, where the asterisk indicates when progesterone was (or was not) added to the cells. From the results, which of the following statements can be concluded? WT PR without progesterone WT PR with progesterone Time Time mutant PR without progesterone mutant PR with progesterone Time Time The wild-type PR is unable to increase FKBP5 expression in the absence of ligand The wild-type PR increases FKBP5 expression after…arrow_forward
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