Transcribe and translate a gene, then break it
Three steps, the way the exam actually works: work through the lab, write down your own observations, then answer a 6-point free response. What you recorded goes to the grader with your writing, so a conclusion that does not follow from your own evidence will cost you the point — exactly as it would with a real reader.
Run the investigation
- 1Run the lab through transcription and translation once from start to stop.
- 2Write down the template DNA strand it generated for you.
- 3Write down the mRNA strand that was built from it.
- 4Write down the amino-acid sequence produced, and count how many codons were read before the stop.
Booting the lab…
Record what you found
This is your reading of the source, not ours. The grader sees them, so your conclusions have to follow from what you actually recorded.
| Template DNA strand | |
|---|---|
| mRNA strand transcribed from it | |
| Amino-acid sequence produced | |
| Codons read before the stop codon |
Answer the free response
Using the strand this lab generated for you: (a) Explain the base-pairing rule that produced your mRNA from your template strand, and account specifically for why no thymine appears anywhere in your mRNA. (b) Identify the codon that began translation and the codon that ended it, and explain what the reading frame is and why it matters. (c) Suppose a single base in the template strand were substituted. Describe the three possible consequences for the resulting protein and name each type of mutation. (d) A single base is instead deleted near the start of the coding sequence. Explain why this is usually far more damaging than a substitution.
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