Principles investigated: DNA, RNA, transcription, translation, amino acids, proteins, protein synthesis, ribosomes, and codons
CA. State Standards:
1d. 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.
4. Genes are a set of instructions encoded in the DNA sequence of each organism that specify the sequence of amino acids in proteins characteristic of that organism. As a basis for understanding this concept:
a. Students know the general pathway by which ribosomes synthesize proteins, using tRNAs to translate genetic information in mRNA.
b. Students know how to apply the genetic coding rules to predict the sequence of amino acids from a sequence of codons in RNA.
Prior Knowledge: Students should be familiar with DNA structure and function and DNA replication including base-pairing rules. Students also covered proteins and know the building block of proteins are amino acids.
Objective: Students will transcribe DNA into mRNA, translate the mRNA, and simulate building a protein using marshmallows and toothpicks as amino acids.
1. 'It's all in the Recipe' data sheet
2. Genetic code key
3. Marshmallow answer key (for the teacher)
3. Large marshmallows
4. Small marshmallows
Procedure: In order to successfully build a protein, students will first transcribe mRNA from DNA on the data sheet.
Base-pairing rules for RNA: A-U
DNA: T A C
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mRNA: A U G
Second, students will then use the mRNA strand they transcribed and translate it into amino acids using the genetic code key. Each mRNA codon (three-letter code) corresponds to a specific amino acid. In this case, each codon corresponds to an ingredient or instruction.
amino acid: Get
Check to make sure transcription and translation are done correctly, then give students the 'amino acids':
They then follow the instructions from the translation and build a 'protein':
Answer questions on back of 'It's all in the Recipe' data sheet and discuss in class.
Video on protein synthesis: