RNAProteinSynthesisSE (2)

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Lone Star College System, Woodlands *

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1303

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Biology

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Apr 3, 2024

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docx

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2019 Name: Cyrano Date: ________________________ Student Exploration: RNA and Protein Synthesis Vocabulary: amino acid, anticodon, codon, gene, messenger RNA, nitrogenous base, nucleotide, ribosome, RNA, RNA polymerase, transcription, transfer RNA, translation Prior Knowledge Questions (Do these BEFORE using the Gizmo .) 1. Suppose you want to design and build a house. How would you communicate your design plans with the construction crew that would work on the house? Blueprints 2. Cells build large, complicated molecules such as proteins. What do you think cells use as their “design plans” for proteins? DNA Gizmo Warm-up Just as a construction crew uses blueprints to build a house, a cell uses DNA as plans for building proteins. In addition to DNA, another nucleic acid, called RNA , is involved in making proteins. In the RNA and Protein Synthesis Gizmo, you will use both DNA and RNA to construct a protein out of amino acids . 1. DNA is composed of the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T). RNA is composed of adenine, cytosine, guanine, and uracil (U). Look at the SIMULATION pane. Is the displayed segment a part of a DNA or RNA molecule? How do you know? DNA, it has thymine and not uracil 2. RNA polymerase is a type of enzyme. Enzymes help chemical processes occur quickly. Drag the yellow RNA polymerase molecule onto the DNA strand. Describe what happens. It splits the DNA
2019 Activity A: Transcription Get the Gizmo ready : If necessary, drag the RNA polymerase molecule onto the DNA strand. Introduction: The first stage of building a protein involves a process known as transcription . In transcription, a segment of DNA serves as a template to produce a complementary strand of RNA. This complementary strand is called messenger RNA , or mRNA. Question: What occurs during transcription? 1. Experiment : Like DNA, RNA follows base-pairing rules. Experiment to find which RNA nucleotide on the right side of the Gizmo will successfully pair with the thymine at the top of the template strand of DNA. (NOTE: The DNA on the right side is the template strand.) Which RNA base bonded with the thymine? adenine 2. Experiment : The next three bases on the DNA template strand are adenine, cytosine, and guanine. Use the Gizmo to answer the following questions: A. Which RNA base bonds with adenine? uracil B. Which RNA base bonds with cytosine? guanine C. Which RNA base bonds with guanine? cytosine 3. Observe : In molecules of RNA, uracil takes the place of the DNA base thymine . 4. Build : Continue building the strand of mRNA until you have used all of the RNA nucleotides. What is the nucleotide sequence of the mRNA strand you built? AUGCUGACCUAG 5. Apply : Suppose a template strand of DNA had the following sequence: T A C G G A T A A C T A C C G G G T A T T C A A What would be the complementary strand of mRNA? A U G C C U A U U G A U G G C C C A U A A G U U 6. Predict : How would a change to the sequence of nucleotides in a DNA segment affect the mRNA transcribed from the DNA? It would change the sequence of the mRNA
2019 Activity B: Translation Get the Gizmo ready : Once the mRNA strand has been built, click Continue . Introduction: After a strand of mRNA has been built, the strand exits the cell’s nucleus. The second stage of protein synthesis, called translation , occurs next. During translation, the strand of mRNA is used to build a chain of amino acids. Question: What occurs during translation? Codon mRNA bases 1 AUG 2 CUG 3 ACC 1. Observe : Examine the strand of mRNA. Each group of three bases of mRNA is called a codon . While the mRNA strand may be longer, translation begins at the universal start codon , which has the bases AUG. In the table at right, list the nitrogenous bases in the first three codons. (Hint: Start from the top of the strand and read down.) 2. Predict : Translation starts when a ribosome (the purple structure on the SIMULATION pane) binds to a strand of mRNA. Transfer RNA , or tRNA, begins bringing amino acids into the ribosome. Each tRNA molecule carries only one kind of amino acid. This amino acid is determined by the tRNA’s anticodon , a set of three unpaired bases. Which anticodon do you think would attach to the mRNA’s start codon? UAC Place this tRNA molecule next to the start codon. 3. Observe : Place the next two tRNA molecules on the mRNA strand. What happens? They build an amino acid and the anticodon breaks off As each tRNA molecule binds to the mRNA, the ribosome joins the amino acid carried by the tRNA to the growing amino acid chain. 4. Describe : UAG (as well as UAA and UGA) is an example of a stop codon . Molecules called release factors bind to stop codons. Place the release factor on the mRNA molecule. What happens? The amino acid chain finishes Click Continue . Your protein is now complete. Most actual proteins consist of sequences of hundreds of amino acids. (Activity B continued on next page)
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