Gene expression essentials

Gene Expression Lab Simulation worksheet adapted by L. McPheron & Shannon Nixon; Phet Simulation by Elizabeth Hobbs; Mutation worksheet by Eliza Woo

Objectives:

● Identify the roles transcription factors, RNA polymerase, ribosomes, and mRNA destroyers have on transcription and translation.

● Distinguish between the location and function of regulatory regions compared to transcribed regions of DNA.

● Predict the effects of concentration, affinity, and degradation rates of transcription factors and RNA polymerase on gene expression.

● Identify the effects of mutations on gene expression. Background: Transcription​ is the process of making mRNA from DNA. This is a highly regulated process that our cells complete in preparation to make a protein. ​Translation​ is the process of making a protein from a piece of mRNA.

DNA --------------------> mRNA --------------------> protein transcription translation

Not all regions of DNA are used to make mRNA - only the parts of DNA that correspond to genes. Even then, not all gene regions are transcribed all the time. When genes are transcribed into mRNA depends on the needs of the cell. Once mRNA is made from DNA, it is translated into protein. Translation is an energy expensive process (it requires LOTS of ATP) which is one reason the cell only completes the process when the protein product is needed. This week’s “Reading and Lesson” explains many of the details of these highly complicated processes, transcription and translation. Please review the lesson for a deeper understanding of the concepts in this lab activity. Procedure: Click the Play arrow on this ​Gene Expression activity​ to complete the simulations. (The simulations are also embedded in the Canvas lab assignment page.) You will complete 3 simulations: 1) Expression, 2) mRNA, and 3) Multiple Cells.

Part 1: Expression Simulation

Click “Expression” to start that simulation. Notice the molecule that spans across the screen, from left to right. Answer the following 2 questions:

1. What is this molecule that spans across the page that is shown in red and blue?

2. What do you think the different colors (red and blue) of the molecule represent?

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https://phet.colorado.edu/en/simulation/gene-expression-essentials
Now, start the process of transcription.

For transcription, you need these things to happen. First, most genes require 1 or 2 “transcription factors” to bind to the area in front of the gene (called the “regulatory region”). Second, an RNA polymerase (an enzyme that makes mRNA from DNA) needs to be present in order for transcription to occur.

1. Drag one Positive Transcription Factor and one RNA Polymerase from the box called Biomolecule Toolbox to the regulatory region on the DNA molecule. This should start TRANSCRIPTION.