Question 11 of 25intermediate💡 UnderstandShort Answer2 marks

Can you now correlate which two properties of genetic code you have learnt?

Correct Answer

The two properties of genetic code are:

1. Degeneracy (Redundancy): One amino acid can be coded by more than one codon. For example, Phenylalanine (Phe) can be coded by both UUU and UUC. This is why when predicting the nucleotide sequence from the given amino acid sequence (Met-Phe-Phe-Phe-Phe-Phe), we face difficulty—we cannot determine which specific codon was used for each Phe residue.

2. Unambiguous nature: Each codon codes for only one specific amino acid. When translating from mRNA to protein, there is no ambiguity—UUU will always code for Phenylalanine only. This makes the forward direction (nucleotide to amino acid) straightforward, unlike the reverse.

Exercise: In-text Question (Page 18) | Q: 12 | (Page 18)
For More Understanding

Explanation

The textbook exercise asks students to predict the nucleotide sequence from the amino acid sequence 'Met-Phe-Phe-Phe-Phe-Phe'. The difficulty faced in this reverse prediction illustrates two key properties: (1) Degeneracy - since 61 codons code for 20 amino acids, multiple codons can specify the same amino acid (e.g., Phe is coded by UUU and UUC), making reverse prediction ambiguous; (2) Unambiguous nature - each specific codon always codes for only one amino acid, making forward translation precise. The codon table in the context shows this degeneracy clearly.

Solution Steps

  1. Step 1: Understand that the exercise involves predicting nucleotide sequence from amino acid sequence

  2. Step 2: Recognize that this reverse prediction is difficult because multiple codons can code for same amino acid (Degeneracy)

  3. Step 3: Correlate that while forward translation is precise (Unambiguous), reverse translation is ambiguous due to degeneracy

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