• Quick retrieval from earlier learning (From gene to protein: transcription and translation). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Where does translation take place? (in the cell membrane / in the mitochondria / at ribosomes in the cytoplasm / inside the nucleus) → at ribosomes in the cytoplasmPrompt: Translation builds the protein.
2. Protein synthesis: which statement is NOT true? (The order of bases decides the order of amino acids. / DNA leaves the nucleus to make proteins. / A gene is a section of DNA that codes for a protein. / Transcription happens in the nucleus.) → DNA leaves the nucleus to make proteins.Prompt: Does DNA ever leave the nucleus?
3. Why is an mRNA copy needed? DNA could be used directly… (DNA is too large to leave the nucleus, so a smaller copy carries the code to the ribosome / Ribosomes are inside the nucleus / mRNA is made of amino acids / DNA is a protein) → DNA is too large to leave the nucleus, so a smaller copy carries the code to the ribosomePrompt: Where are ribosomes found?

• Show a microscope image of cells and ask what students think they are looking at.
• Share the objective: Bases, codons and amino acids: genetic code calculations. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: A protein contains 141 amino acids. What is the minimum number of mRNA bases needed to code for it (ignore the stop codon)?
• Step 1: 141 × 3 = 423
• Step 2: So the answer is: 423
• Answer: 423
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. A protein contains 50 amino acids. What is the minimum number of mRNA bases needed to code for it (ignore the stop codon)? → 150Prompt: Each amino acid is coded by one codon.
2. The coding part of an mRNA molecule is 156 bases long, including one stop codon at the end. How many amino acids are in the protein? → 51Prompt: Divide by 3 to find the number of codons.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. The coding part of an mRNA molecule is 453 bases long, including one stop codon at the end. How many amino acids are in the protein? → 150Prompt: Divide by 3 to find the number of codons.
2. A protein contains 141 amino acids. What is the minimum number of mRNA bases needed to code for it (ignore the stop codon)? → 423Prompt: Each amino acid is coded by one codon.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-11.