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Title: Protein Synthesis
Principle(s) Investigated:
Protein Synthesis
Translation
Transcription
Biology/Life Sciences 9th-12th grade
Cell Biology 1.d. Students know the central dogma of molecular biology outlines the flow of
information from transcription of ribonucleic acid (RNA) in the nucleus to translation
of proteins on ribosomes in the cytoplasm.
Cell Biology 4.a. Students know the general pathway by which ribosomes synthesize proteins,
using tRNAs to translate genetic information in mRNA.
Cell Biology 4.b. Students know how to apply the genetic coding rules to predict the sequence of
amino acids from a sequence of codons in RNA.
Cell Biology 4.e. Students know proteins can differ from one another in the number and sequence
of amino acids.
Materials:
mRNA strips of paper for each group
DNA molecules
Anti-codon and corresponding word pages
Scissors
Paper
Pencils
Tape
Procedure:
1. Cut out DNA molecules and tape them to one area of your room. Label this area the nucleus.
2. Tape the cytoplasm label to the front of the room.
3. Tape the tRNA’s with the anti-codon facing the students. They should not be able to see the amino acid/word side.
4. Tape ribosome labels on each students desk (or one per group).
5. Group the students in pairs and explain the instructions. I would have the directions left on the board to avoid any confusion.
6. Give each group three mRNA pieces of paper and one normal size printer piece of paper.
7. One student in the group goes to the nucleus and transcribes the DNA code from the nucleus to the mRNA molecule. The student will write down the codons into the spaces (3 letters per space).
8. That student returns to desk and places that mRNA code onto the ribosome (their desk).
9. The other partner translates the code (in the ribosome) and will go up to the front and find the tRNA with the corresponding anti-codons. That student will bring that paper back to the ribosome.
10. The other student (who went to the nucleus) then writes the corresponding word on the other side of the tRNA down on the paper.
11. The tRNA student returns the paper back to the front of the classroom and goes through the process again until the message is transcribed and translated.
12. The students continue to make the sentence until they receive the “STOP” word (or the stop codon).
13. You can have students make three sentences for an assessment.
Student prior knowledge:
· Students would need to have a thorough understanding of DNA base pairing and the way DNA base pairing works in regards to DNA and the corresponding mRNA and tRNA.
· They would also need to understand the importance of proteins and have some knowledge about how amino acids are essentially the building blocks for proteins.
· They would also have learned about ribosomes and the function of ribosomes in the cell.
· This activity is designed to be done after instruction has been given on protein synthesis.
Explanation:
· Protein Synthesis is the process by which biological cells generate new proteins.
It is important to note that this is balanced by the degradation or export of other cellular proteins.
· The two main processes that will be described in this lesson and in which is activity is designed to solidify is translation and transcription.
· In transcription an mRNA (messenger RNA) chain in generated. One of those strands of the mRNA is made up of the DNA double helix genome template- therefore this strand is called the template strand.
· Transcription occurs in the cell nucleus where the DNA is held. The DNA double helix is unzipped by certain enzymes and then the mRNA is synthesized by the appropriate base pairs. It is very important to understand that the nucleotide Uracil takes the place of Thymine that is normally in the DNA. Therefore, A,T,G, and C will be the nucleotides you would see in a DNA strand and A,U,G, and C will be the nucleotides you would see in a RNA strand. A pairs with T and G pairs with C in DNA. A pairs with U and G pairs with C in RNA.
· Once the mRNA is created from the DNA the single strand of mRNA leaves the nucleus through the nuclear pores and moves into the cytoplasm.
· Translation is the process in which the proteins are actually synthesized and this takes place in the cytoplasm, where the ribosomes are located.
· After the mRNA is in the ribosome then the tRNA (transfer RNA) must use the anti-codons (opposite nucleotides) to match up to the mRNA.
· The tRNA has a specific amino acid on the end of it and when that attaches the amino acids become bound together and are further synthesized as proteins.
· Note: It is important to watch and show videos to your class because this process is very hard to understand without a good visual description of the steps.
This activity is designed to be performed after some direct instruction has been delivered on the process of protein synthesis. By going through the steps and having this hands-on approach to learning the hope is that the students will solidify the protein synthesis process in their minds and will then be able to gain a deeper understanding of why each step takes place.
Questions & Answers:
1. Have you ever used something or some process involving protein synthesis?
Yes, protein synthesis has now become an integral part of the modern world. See applications to everyday life.
2. Why must mRNA be synthesized in the nucleus? Why can the cell not just use the DNA as a template in the cytoplasm?
mRNA must be synthesized in the nucleus because the double helix DNA molecule is too large to pass through the nuclear pores of the nucleus and move to the ribosomes for translation.
3. Would a point mutation or a frameshift mutation be more harmful to DNA ?
A point mutation would be a change in one nucleotide to another nucleotide where as a frameshift mutation would be the complete removal of a nucleotide and would end up having all of the codons be read in a different manner. In terms of a point mutation there is a chance that the mutation could still code for the amino acid and there is also a chance that the codon could code for another amino acid that would not end up being harmful to the organism. In terms of frameshift mutation, almost all of the corresponding amino acids would change and the protein would not be anything like the desired product. There are exceptions to this if the point mutation is located in the start or stop codons.
Applications:
1.Immunobiology
Proteins allow cells to detect and react to toxins in their surroundings. Proteins are the main ingredients in antibodies which are important for helping our bodies resist infection and protecting our bodies from foreign invaders and antigens. Proteins also promote growth and repair of bone, muscles, tissues, blood, and organs. Scientists have found that cancer cells will use the body’s machinery and either create an overexpression of unwanted proteins or repress proteins needed to have a successful immune function.
2. Wine
Proteins need to be synthesized to catalyze food and drink reactions. If we did not have proteins our wine would not be what it is today. There are enzymes called enological enzymes that catalyze reactions and are involved in enhancing wine stability and improving overall quality. For example, pectic enzymes can degrade pectins to provide stability against cloudiness or to improve fining and filtering efficiencies. Mannoproteins are also important in wine. Not only does the release of mannoproteins impart sensory changes in the wine but they can contribute in helping enhance the body and mouthfeel of the wine as well as decrease the bitterness of wine.
3. Evolution
Proteins are key in providing scientists with phylogenetic trees to be able to construct evolutionary hypotheses. Scientists and researchers are able to identify homologous proteins in distantly related organisms and then use sequencing profiling tools to construct an evolutionary tree. Because of updated technology, scientists and researchers have been able to more quickly analyze data and have created fields such as bioinformatics.
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Videos:
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