Final answer:
A mutation in DNA, such as the replacement of cytosine with adenine, affects the base-pairing during transcription and changes the corresponding mRNA sequence. This alteration can lead to changes in the encoded amino acid sequence, potentially affecting the protein's structure and function.
Step-by-step explanation:
When a mutation occurs in DNA, such as the replacement of cytosine with adenine, the base-pairing rules are affected during transcription into mRNA. Typically, adenine (A) pairs with uracil (U), cytosine (C) pairs with guanine (G), and guanine (G) pairs with cytosine (C). However, if in the DNA strand cytosine is replaced by adenine due to a mutation, the subsequent mRNA would have uracil (U) in place of where guanine (G) would have paired with the original cytosine (C).
The wobble base concept suggests that a change in the third base of the codon may not always affect the resulting amino acid due to the redundancy of the genetic code; however, this is specific to the third base and would not apply to a mutation in the first or second base.
Using the example provided, if the DNA sequence 5'-AATTGCGC-3' experienced a mutation where cytosine is replaced with adenine, the complementary mRNA would normally be 3'-UUAACGCG-5', but due to the mutation, it would change at the mutated point, leading to a possible change in the encoded amino acid and subsequent alterations in the protein structure and function.