STEM Case - Protein Synthesis (Gizmo) PDF

Preview

Summary

Name: Sung-Ha You Date: Jan 7, 2021Student Guide: Protein SynthesisIntroduction : Lucy is a baby girl who comes to see the paediatrician because she has been getting a lot of ear and skin infections. In this activity, you will learn about genes and protein synthesis to try to help Lucy.Vocabulary : ...

Description

Name: Sung-Ha You

Date: Jan 7, 2021

Student Guide: Protein Synthesis Introduction: Lucy is a baby girl who comes to see the paediatrician because she has been getting a lot of ear and skin infections. In this activity, you will learn about genes and protein synthesis to try to help Lucy. Vocabulary: As new vocabulary is introduced, the words are presented in the Gizmo as orange text - clicking the orange text opens the glossary page for that term. You can use the glossary at any point. 1. Lucy does not have enough white blood cells for her immune system to fight infections. Was this caused by human immunodeficiency virus (HIV) or ADA Severe Combined Immunodeficiency (ADA-SCID)? Lucy’s test results revealed that she has ADA-SCID. This is because when we collected her HIV Proteins, there were none present, however, when we collected her deoxyadenosine levels, they were a lot higher than the normal range. If a patient has ADA-SCID, their blood will show high concentrations of deoxyadenosine, which is the same for Lucy.

2. Describe the cause and effects of each kind of mutation below: a. Active site mutation: With Lucy’s condition, ADA has an active site for the toxin, deoxyadenosine, to be broken down. However, an active site mutation is caused by a change in an amino acid in that ADA’s active site due to a DNA mutation. This would cause a different shape of the site and it would not be able to break down the toxin.

b. Stop codon mutation: A mutated sequence with a stop codon mutation will create a stop codon too early in the amino acid sequence. Since stop codons end the translation process of a protein, this mutation will cause the protein to be not made correctly, because it will be shorter in length.

c. tRNA Error:

1

A tRNA error occurs when a mutation causes tRNA molecules to carry the wrong amino acids. This is important because it will cause the proteins to not be made correctly.

3. Answer the following questions for the experiments performed: i. What was the experiment investigating? ii. What was done during the experiment? iii. What did the result prove? a. Experiment 1: i) This experiment was investigating the translation of Lucy’s ADA enzyme, to see if her tRNAs were carrying the correct amino acids. ii) During the experiment, Lucy’s tRNA molecules in her white blood cells were tested to see if it was carrying the correct amino acid for its anticodon. Using the RNA pairing rules, the codon was determined, as well as the amino acid. The first tRNA was determined to carry glycine which is the correct amino acid, meaning it was working correctly. After scanning the rest of the tRNA molecules, all of them matched the correct amino acids. All tRNA was normal. iii) This result proved that Lucy’s mutation was NOT a tRNA error, because all tRNA were carrying the correct amino acids.

b. Experiment 2: i) This experiment was investigating the sequence of nucleotides in Lucy’s ADA mRNA transcript, and to see if it had been changed by a mutation, causing the enzyme not to work. ii) After scanning for mutations, there was a mutation in ADA’s active site. The codon had been changed from GAC to GAU. The first mutation did not change the amino acid, and was a silent mutation. However, the second mutation changed the codon from CGA to UGA. Instead of coding for the amino acid arginine, it instead coded for a stop codon. iii) These results ruled out Lucy’s tRNA carrying the wrong amino acids, and instead found a stop codon mutation at codon #284. This resulted in her ADA enzyme from 363 amino acids to 283 amino acids, shortening it. This would cause her ADA enzyme to not work.

2

4. Which mutation caused Lucy’s immunodeficiency disease? Explain how this mutation stopped her ADA protein from working. The stop codon mutation caused Lucy’s immunodeficiency disease. This mutation created a stop codon too early in the amino acid sequence. Stop codons are supposed to end the translation process, so with this. mutation, it shortened the ADA enzyme from 363 amino acids to 283 amino acids. With being such a short length than normal, this causes Lucy’s disease and enzyme to not work, not providing the proper function of a protein.

5. Your scan of Lucy’s ADA gene showed a mutation in the active site. Why was this mutation not a problem? The mutation in the active site was not a problem, because it was a silent mutation. Although the codons were changed (GAC to GAU), these codons actually code for the same amino acid (Aspartic Acid) by using the codon wheel. Since it was a silent mutation, and the amino acid stayed the same, this resulted that the shape of the active site stayed the same. Therefore, this mutation was not a problem in Lucy’s case.

6. Explain how stem cell therapy helped Lucy break down deoxyadenosine. Stem cells are able to change into other types of cells. Stem cell therapy helped Lucy in the case where they can be changed into white blood cells. With the help of white blood cells working with ADA enzymes, they are able to break down the toxin. In Lucy’s case, the white blood cells needed are found in the bone marrow, which Lucy will undergo a surgical procedure to remove a sample of her bone marrow. They will be placed under a petri dish to in optimal conditions keep them healthy. With the help of the technology CRISPR/Cas9, the stem cells are able to duplicate and grow so Lucy can have many (millions) of these healthy cells! Finally, the stem cells will be put back into her bone marrow and change into healthy white blood cells. She will now be able to break down the toxin and have a strong immune system.

3...