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Explain how a single base substitution causes a change in the structure of this polypeptide - AQA - A-Level Biology - Question 2 - 2019 - Paper 1
Question 2
Explain how a single base substitution causes a change in the structure of this polypeptide. Do not include details of transcription and translation in your answer.
Worked Solution & Example Answer:Explain how a single base substitution causes a change in the structure of this polypeptide - AQA - A-Level Biology - Question 2 - 2019 - Paper 1
Step 1
Change in the Sequence of Amino Acids
Answer
A single base substitution in the DNA sequence can lead to the production of a different amino acid in the polypeptide chain. This change occurs because the genetic code is composed of triplet codons, where each codon corresponds to a specific amino acid. Hence, substituting one base may alter a codon, thus changing the corresponding amino acid in the sequence.
Step 2
Alteration of Ionic and Disulfide Bonds
Answer
The substitution might also affect ionic and disulfide bonds within the polypeptide structure. The properties of the new amino acid, such as its charge or ability to participate in disulfide bonding, can influence how these bonds form and stabilize the structure of the polypeptide.
Step 3
Impact on Tertiary Structure
Answer
Finally, a single base substitution can change the folding pattern of the polypeptide, leading to a different tertiary (3D) structure. The altered interactions between amino acids, which arise from the original substitution, can disrupt the overall folding and functionality of the protein.