component 1: arrival


The species and quantities of proteins created by a given cell in the human body are very important and carefully regulated. Transcribing DNA come messenger RNA and also translating the RNA come protein is frequently referred to together gene expression. Regulating the expression simply means turning on or turn off or raising or diminish the manufacturing of a given protein. Interestingly, protein production can be regulation at the translational and also transcriptional steps, as well as after a protein is produced. In this activity, we will certainly talk about how gene expression is regulated through transcription.

The simple elements of transcription regulation in standard scale are comparable to the an extremely well-studied lac and trp operon systems found in bacterial cells. In both eukaryotic and bacterial solution a protein, either an activator or repressor, binds to a region of the DNA called an “operator” in prokaryotes and a “regulatory switch” or “enhancer” in eukaryotes. The activator or repressor protein acts favor the hand that flips the switch, however it can only rotate the move on or turn off if it can bind come the certain DNA sequence.

You are watching: Modeling the regulatory switches of the pitx1 gene

Gene regulation is necessary for the cabinet to carry out the attributes needed come live. In multicell eukaryotes, gene regulation is likewise important in building bodies. During development, various sets the genes must be rotate on and also off in the appropriate places, at the appropriate times, and in the best sequence for bodies to be built correctly. In this activity, you will learn about one details gene, Pitx1, and how that expression is regulation in various tissues.


Watch the short film, The making of the Fittest: Evolving Switches, Evolving Bodies. Pay close fist to just how the switches control the expression of the Pitx1 gene in stickleback embryos.


Use the information from the film and also your understanding of eukaryotic gene transcription to answer questions 5-9.

4. Number 1 is a diagram, similar to the one displayed in the film (8:00-8:34), showing crucial components of gene transcription. Label the boxes in figure 1 with the letters a-e, which exchange mail to the terms noted below. Because that example, write letter “a” in package pointing in ~ the protein-coding region.

a. Protein-coding an ar b. Regulation switches (or enhancers) c. Promoter d. MRNA e. RNA polymerase


5. Gene transcription is a complicated process that involves interactions that proteins and regulatory regions of DNA. Transcription factors specifically bind come the promoter to activate transcription. Various other proteins play a function in this regulatory regions. Explain the function of each of the following, making use of the photo to aid you.


activators enhancers mediators RNA polymerase


As you observed in the film, the existence or lack of pelvic spines in the stickleback fish is controlled by even if it is the Pitx1 gene is express in the pelvic tissue. However, the Pitx1 protein is actually necessary in building other human body parts and also is as such expressed in multiple organization at details times.

How is Pitx1 express in various tissues? The Pitx1 gene has actually multiple regulatory switches that control the expression the the gene in different tissues: the pituitary, jaw, and also pelvic tissues. Having actually multiple switches permits Pitx1 to be used plenty of times in various contexts and also expands the adaptability of that gene. Activators current in a particular tissue bind to a particular sequence ~ above the DNA and turn Pitx1 top top in the suitable tissues. Because that example, in the cells that develop into the pelvis there is a particular activator (activator 2) that binding to the pelvic switch to transcribe Pitx1 in the tissue. In the jaw, over there is a various activator (activator 1) that binding to the jaw switch to revolve on Pitx1 in the jaw tissue.


Figure 2 illustrates how Pitx1 warrior is regulated in different tissues. The facility image is the of a stickleback embryo. The illustrations in the neighboring boxes show the Pitx1 gene an ar and activator proteins existing in the jaw, pelvis, eye, or pituitary tissues. Note that for simplicity, we are only showing one activator molecule current in a specific tissue. In reality, plenty of activators are existing in a details tissue at any one time. Activator molecules with specific shading can bind come switches v the exact same shading.

See more: Who'S Olivi A Series Of Unfortunate Events Olivia Caliban

6. Perform all the tissues presented in figure 2 the express the Pitx1 gene:

7. Take into consideration what to be revealed in the film. How have the right to a spined stickleback fish have the specific same PitX1 sequence as a spineless stickleback?

8. Study the table, if a mutation emerged in the activator region, which areas would you expect to express the Pitx1 gene. Examine all that would apply.






Activator 1

Activator 2

Activator 3

Activator 4

9. The Pitx1 protein has plenty of important attributes in assorted tissues throughout stickleback development. The complete absence of Pitx1 protein from all tissues is lethal to the organism. Circle the fish listed below that lacks Pitx1 expression in the pelvis and also EXPLAIN your choice.