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AQA A Level Biology Practice Questions (chapter 2)

If anyone could explain the answer to this question at the end of chapter 2, it would be greatly appreciated!

2c) Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease? Why is the answer not 254? And why does the mark scheme have 381/384/387 as possible answers?
Reply 1
Original post by haylekins
If anyone could explain the answer to this question at the end of chapter 2, it would be greatly appreciated!

2c) Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease? Why is the answer not 254? And why does the mark scheme have 381/384/387 as possible answers?

How many bases are needed to code for one amino acid? (hint: codons, and the process of translation)
Remember that translation just involves one strand (mRNA) so no need to multiply by 2.

The 384 and 387 values presumably are referring to start/stop codons :smile:
(edited 3 months ago)
Reply 2
Original post by bl0bf1sh
How many bases are needed to code for one amino acid? (hint: codons, and the process of translation)
Remember that translation just involves one strand (mRNA) so no need to multiply by 2.

The 384 and 387 values presumably are referring to start/stop codons :smile:

Thank you! Codons are not mentioned at all in chapter 2 so seems like an odd place for this question!
(edited 2 months ago)

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