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Ch. 17+18 - Transcriptional Regulation in Eukaryotes
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All textbooksKlug 12th EditionCh. 17+18 - Transcriptional Regulation in EukaryotesProblem 28

Chapter 17, Problem 28

Marine stickleback fish have pelvic fins with long spines that provide protection from larger predatory fish. Some stickleback fish were trapped in lakes and have adapted to life in a different environment. Many lake populations of stickleback fish lack pelvic fins. Shapiro et al. (2004) (Nature 428:717.723) mapped the mutation associated with the loss of pelvic fins to the Pitx1 locus, a gene expressed in pelvic fins, the pituitary gland, and the jaw. However, the coding sequence of the Pitx1 gene is identical in marine and lake stickleback [Chan et al. (2010). Science 327:5963,302–305]. Moreover, when the Pitx1 coding region is deleted, the fish die with defects in the pituitary gland and the jaw, and they lack pelvic fins. Explain how a mutation near, but outside of, the coding region of Pitx1 may cause a loss of pelvic fins without pleiotropic effects on the pituitary gland and jaw.

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Hi, everybody. Let's take a look at this practice problem together, determine which of the following characteristics is shared by an enhancer and a silencer. Now recall that they are both regulatory elements and more specifically both are cis regulatory elements. Cis regulatory elements regulate the transcription of nearby genes on the same chromosome. So we know that enhancers should activate or enhance transcription and silencers repress transcription. So let's take a look at our options. We've got b they both are present in the coding region now because they are both cis regulatory elements, those are located in the non coding regions. So B is incorrect. See, they both decrease the activity of a gene. This is also false. We know that only silencers decrease the activity. Option D is all of the above. So we can eliminate it. That means the answer is a, they both are tissue specific since both control gene expression, they can be tissue specific since different tissues need different gene expression levels. Therefore, A is the correct answer. Alright, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.
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