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There is A LOT to unpack in Lesson 3.03. Before you attempt the quiz that comes after Lesson 3.03 make sure you have spent adequate time understanding the material in the lesson and types of questions you will see on the quiz. Complete the following tasks.
Task 1: Review what you have learned about proteins from other lessons.
Lesson 1.02: Proteins are a type of macromolecule that are made up of amino acids. The word protein comes from the Greek word proteios, meaning "first place." This indicates how important they are to living organisms. Proteins make up more than 50 percent of the dry weight of cells, and they are important to almost every function of a cell.
Lesson 2.03: Ribosomes are an organelle found in cells. They are responsible for making proteins. Ribosomes can be found floating in cytoplasm and attached to endoplasmic reticulum.
Task 2: Understand the BIG idea in this lesson.
Protein synthesis is just a fancy way to say…make a protein. This lesson is all about understanding how proteins are made. Cells cannot make proteins directly from DNA. They need the help of RNA. DNA contains the instructions for making proteins. RNA copies sections of DNA and then carries the copies to ribosomes where proteins are made.
Cells use a two-step process of transcription and translation to read each gene and produce the string of amino acids that makes up a protein. The process of making a protein follows these steps: DNA → mRNA (transcription) → protein (translation).
This flow of information is called the central dogma of biology.
Task 3: Understand the types of questions you will see on the quiz.
Some questions will simply ask you to identify the definitions for the following words: anticodon, mRNA, tRNA, rRNA. Remember, the list of vocabulary and their definitions can be found on the next to the last page of the lesson.
Some questions will ask you to identify the different parts of a picture similar to this one on page 3 of the lesson.
Some questions will ask you to identify the differences between DNA and RNA. You can practice that below. (Note: If you don't see the practice below refresh your screen.)
Some questions will ask you to identify the steps of transcription and translation. You can review those below.
Some questions will give you a triplet of DNA bases and ask you to determine the corresponding codon for mRNA. To do that you will follow base pairing rules for transcription. You can practice this in the transcription activity below. (Note: If you don't see the activity below refresh your screen.)
Some questions will ask you to determine the codon on the mRNA molecule that pairs with the given anticodon of a tRNA molecule . When the question gives you a tRNA anticodon, it's asking you to "reverse" the pairing process to figure out what codon on the mRNA would have matched it. See the example and steps to solve below.
If a tRNA molecule has an anticodon which reads GCAUUG, what was the codon on the mRNA molecule? Begin by writing the anticodon and the add the the the complementary mRNA bases for the anticodon sequence (replacing U with A, A with U, G with C, and C with G). The mRNA sequence for the anticodon GCAUUG is CGUAAC .
Now it is your turn! If a tRNA molecule has an anticodon which reads UACGAU, what was the codon on the mRNA molecule? Check your answer here.
Some questions will ask you to be able to read a codon chart. Watch this video for a tutorial and practice your skills below. (Note: If you don't see the activity below refresh your screen.)
Some questions ask you to transcribe from DNA to mRNA and then translate from mRNA to amino acids. Practice below using the amino acid chart on the left. If you need help getting started, watch this short video.
Some questions may give you an mRNA sequence and ask you to transcribe it to tRNA to determine the amino acid sequence that would form. See this example.
Before you move on to Task 4, practice vocabulary from Lesson 3.03 below.
Task 4: Take the practice quiz here.
Once you have completed all the tasks you are ready to take the quiz!
Once you have completed all the tasks you are ready to take the quiz!
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