RNA and Protein Synthesis Gizmo Student SE

Centennial High School (Maryland) - Ellicott City

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Student Exploration: RNA and Protein Synthesis

Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.

Vocabulary: amino acid, anticodon, codon, gene, messenger RNA, 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?

I would draw up a blueprint so the construction crew can see the plan in detail

1. Cells build large, complicated molecules, such as proteins. What do you think cells use as their “design plans” for proteins?

Cells use DNA as their design plans, for it contains all the necessary genetic coding.

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 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?

This is part of a DNA molecule because of its double helix structure

1. RNA polymerase is a type of enzyme. Enzymes help chemical reactions occur quickly. Click the Release enzyme button, and describe what happens.

RNA polymerase split the helix into two separate strands.

Get the Gizmo ready: ● If necessary, click Release enzyme.

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 paired with thymine

1. 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 and Thymine

B. Which RNA base bonds with cytosine? Guanine

C. Which RNA base bonds with guanine? Cytosine

In molecules of RNA, uracil takes the place of the DNA base

1. 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? ATUAGCCGUAGCATCGCG USATGC

1. 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

1. Predict: How would a change to the sequence of nucleotides in a DNA segment affect the mRNA transcribed from the DNA?
2. Infer: Why do you think stop and start codon signals are necessary for protein synthesis?

Without start and stop codons, the ribosome wouldn’t know when the protein is complete or the strands of mRNA need to be read. Without these important codons, protein synthesis wouldn’t occur as it should, and an error can occur and cause a mutation.

1. Summarize: Describe the processes of transcription and translation in your own words, based on what you have observed in the Gizmo.

Transcription: Transcription occurs in the nucleus where DNA coding is converted to mRNA.

First the double helix is unzipped with the help of RNA polymerase. While

each of the bases are exposed, the mRNA nucleotides pair with their

complementary bases so the molecule can grow. The mRNA strand then

detaches from the DNA and goes on to begin translation.

Translation: Translation is where the mRNA is scanned and codons are read after each

other in order to make a protein. The tRNA molecules containing anti codons

enter ribosomes where they are matched with a part of the gene once it

reaches the correct base pairs. As this happens, the amino acids are attached

to the proteins until the a stop codon is reached.

Genes and traits

Get the Gizmo ready: ● You will not need to use the Gizmo for this activity.

Introduction: Inside a ribosome, amino acids are linked together to form a protein molecule. As the chain of amino acids grows, it folds and coils to form a three-dimensional shape. The complex shape that results determines the properties of the protein. Proteins have a wide variety of structures and perform many essential functions in living things.

A sequence of DNA that codes for a specific protein is called a gene. By coding for proteins, genes determine an organism’s inherited traits.

Question: How do genes code for specific proteins and traits?

1. Translate: Each codon codes for one of 20 amino acids. This code is universal among all living things. For example, the mRNA codon GGU codes for the amino acid glycine in every living thing, from a bacteria to an elephant.

Examine the codon chart below. The amino acid coded for by a specific mRNA codon can be determined by finding the first base of the codon along the left side of the table, the second base along the top of the table, and the third base along the right side of the table.

What amino acids do the following codons code for?

AUG: Methionine CUG: Leucine ACC: Threonine UAG: Stop