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One section of a polypeptide has the amino acid sequence Ala – Cys – Lys – Ile – Asn The codons for these amino acids are: Ala GCA GCC GCG GCU Cys UGC UGU Lys AAA AAG Ile AAU AUC AUA Asn AAC AAU The sequence of DNA coding for this section of the polypeptide could be: A - VCE - SSCE Biology - Question 20 - 2006 - Paper 1
Question 20
One section of a polypeptide has the amino acid sequence Ala – Cys – Lys – Ile – Asn The codons for these amino acids are: Ala GCA GCC GCG GCU Cys U... show full transcript
Worked Solution & Example Answer:One section of a polypeptide has the amino acid sequence Ala – Cys – Lys – Ile – Asn The codons for these amino acids are: Ala GCA GCC GCG GCU Cys UGC UGU Lys AAA AAG Ile AAU AUC AUA Asn AAC AAU The sequence of DNA coding for this section of the polypeptide could be: A - VCE - SSCE Biology - Question 20 - 2006 - Paper 1
Step 1
The sequence of DNA coding for this section of the polypeptide could be:
Answer
To determine the correct sequence of DNA that codes for the polypeptide of amino acids Ala, Cys, Lys, Ile, and Asn, we first identify the codons for each amino acid provided in the table.
- Ala (Alanine) has codons: GCA, GCC, GCG, GCU
- Cys (Cysteine) has codons: UGC, UGU
- Lys (Lysine) has codons: AAA, AAG
- Ile (Isoleucine) has codons: AAU, AUC, AUA
- Asn (Asparagine) has codons: AAC, AAU
Next, for each codon, we convert them back to their corresponding DNA sequences, replacing uracil (U) with thymine (T):
- Ala (GCA) corresponds to: CGT
- Cys (UGU) corresponds to: ACA
- Lys (AAA) corresponds to: TTT
- Ile (AAU) corresponds to: TTA
- Asn (AAC) corresponds to: TTG
Thus, the potential DNA sequences for the polypeptide are:
- CGT (Ala) AC (Cys) TTT (Lys) TTA (Ile) TG (Asn)
From the options given, performing this conversion shows that option A: CGTACGTTTTG corresponds correctly as it closely follows the required sequence structure aligning to the respective amino acids.