Engage - Nucleic Acids and Proteins

Chances are you've heard of proteins in terms of your diet. Or maybe you have heard that meat, soy, and other foods are good sources of proteins. Also, the chances are good that you've heard of DNA, the nucleic acid that is the blueprint of your genetic inheritance. Do you know that nucleic acids and proteins are highly important to cellular function? Watch the video below for a brief introduction to the relationship between these two types of biomolecules.

Central_dogma.mp4

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Aren't you glad nucleic acids create proteins to help living organisms function? That's a lot of production from such small factories. Take a moment to check your understanding about the roles of molecules during transcription and translation by answering the questions below. If you get stuck, just replay the movie.

Explore, Part 1: Steps in a Process

One thing you learned in the Engage section is that protein synthesis involves a series of steps to get the job done. It's similar to the process a cook uses when a recipe guides the cooking staff as they prepare food. In this section, we'll focus on a few more details in the process that starts with genes and ends with proteins for your body to use.                                         

To check your critical thinking skills, proceed to the Basic Sequence quiz below and order the steps of protein synthesis in a way that you think makes sense. Don't worry! This is not a real quiz.

Precheck

Your challenge is to attempt to sequence the steps in the protein synthesis process in the activity below. It's ok if you don't really know them yet. Just order them in a way that you feel is logical.

 

Postcheck

 

 

 

 

 

 

 

Next, open the pdf document titled "Protein Synthesis." You can also open the document in the Related Items section below. Analyze the graphics and pay close attention to the sequence of steps as well as which molecule is involved in each step. Once you've finished your analysis of the graphic, try the sequencing activity again. If your goal is to get 100% correct without guessing, then you're on the right track!

Source: 
Public domain image captured from http://publications.nigms.nih.gov/structlife/ch1_fold.htm 1/13/2013

Explore, Part 2 - Transcription

Cells produce or synthesize different proteins for different functions, from cell structures to hormones, enzymes, and even the hair on your head. It's nonstop production for the life of an organism. According to information from the Human Genome Project, humans have approximately 20,500 genes that produce tens of thousands of proteins for our bodies!

It's the number and sequence of DNA nucleotides that determine the RNA molecule synthesized as a transcript in the nucleus of the cell. Examine the graphic below. It displays the bonding pattern of the four DNA and RNA nucleotides.

Examine the image below. The sense strand represents the genetic code for the protein that will be produced during translation. To make a copy or replica of the code, messenger RNA nucleotides align to the antisense side of the DNA molecule. You can tell it is an exact replica of the gene because the nitrogen bases are in the same order as the sense strand. The only difference is the uracil substitution for thymine, which is appropriate.

This image is in the public domain "Courtesy: National Human Genome Research Institute."

Now it's your turn to practice matching RNA nucleotides to a DNA antisense strand. Click the image to access an interactive animation where you get to play the role of RNA polymerase. The animation opens in a new window. When you are finished close the window to return to the resource.

Source: 
The animation by Cold Spring Harbor Laboratory is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

Explore, Part 3 - Translation

The image you see below depicts translation, the second major step in the process of protein synthesis. The image across the top is of ribosomes translating mRNA codon messages into proteins. Examine the expanded ribosome graphic closely.

First, look for labels identifying mRNA, tRNA, and ribosome. All three of these molecules are different types of RNA that perform different functions. What functions do you think each molecule performs?

Next, look for the words codon and anti-codon. Do you see any patterns? (Hint: Look for grouping and bonding patterns.)

Now, focus on the tRNA molecules. Transfer RNA 1 is adding an amino acid to a peptide chain to make a protein. Two more tRNA molecules are in line to add their amino acid to the chain. Why doesn't tRNA 3 line up in front of tRNA 2? Proceed to the text below the image for the next activity.

This image is in the public domain "Courtesy: National Human Genome Research Institute."

In this activity, you will take on the role of transfer RNA in the translation from nucleic acid to protein language. Before you click the image to begin the activity, make sure to note the base-pair matching pattern. You'll need the information to synthesize your protein correctly.

The interactive animation opens in a new window. When you are finished, close the window and continue learning about protein synthesis.

Source: 
The animation by Cold Spring Harbor Laboratory is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

In this next activity, you have a chance to play the role of transfer RNA from a slightly different perspective. This time you will process translation from the amino acid sequence backwards to the mRNA codon. For example, as tRNA, your assigned amino acid is valine. Which mRNA codons specify the amino acid valine in the protein sequence? Use the chart below to determine the correct codons.

This image is in the public domain "Courtesy: National Human Genome Research Institute."

If you identified the mRNA codons GUU, GUC, GUA, and GUG as the appropriate matches, then you are ready for the challenge. You will need to open a word document or your science journal, grab paper and pen, or use a note-taking app to proceed.

Copy the amino acid sequence below in a single line. Use the abbreviations in the chart to help save space. Below each amino acid, list all the mRNA codons that represent an appropriate match for you, as a transfer RNA anticodon. When you have finished, open the Transfer RNA Quality Control Manual to see how well you've done.

Methionine - Histidine - Serine - Aspartic Acid - Tryptophane - Arginine - Leucine - stop

Explain - Digging Deeper

Click the play arrow below to find out how the pre-mRNA transcript is edited prior to leaving the nucleus for translation into protein language. Click the X in the video window when you are finished watching and move to the last section.

 

This video was captured from You Tube 3/23/13

Trimming the introns out of the pre-mRNA transcript might remind you of making edits to a rough draft of a writing assignment before turning it in. Unlike eukaryotes, prokaryotes don't edit the mRNA transcript at all. In fact, since they don't have a nucleus, both transcription and translation take place in free-floating ribosomes in the cytoplasm.

Source: 
This work by Cold Spring Harbor Laboratory is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

Elaborate - RNA Has Hidden Talent

DNA is definitely the molecule of life, but it has certain limits when it comes to protein production. That's a good thing because when a code is copied thousands of times, it should be dependable. The more versatile nucleic acid is RNA because it has a variety of forms that not only enable the tasks of transcription and translation, but also make sure the quality of the protein produced is consistent.

View the video below to see for yourself.

Source: 
Video courtesy of © 2012 PBS & WGBH Educational Foundation. All rights reserved.

RNA, in its many forms, is highly important to the management of the gene expression process known as protein synthesis. Now scientists are learning how to use RNAi and other RNA molecules to develop therapies and treatments for disease.

Source: 
The RNAi 3D animation is a Nature Video by NRG/Arkitek and downloaded from YouTube 4/17/13.