Final answer:
An insertion mutation alters the DNA sequence by adding nucleotides, potentially changing the protein coded by the gene. A specific example of cytosine replaced by adenine is a point mutation that affects base pairing and protein synthesis. Insertions of three nucleotides may avoid frameshift effects seen in single-nucleotide insertions.
Step-by-step explanation:
An insertion mutation occurs when one or more nucleotides are inserted into the DNA sequence. This can significantly impact the DNA since the insertion changes the codon where it occurs and alters all subsequent codons. This type of mutation can result in a frameshift, which means that every amino acid coded for after the mutation can be different, potentially changing the function of the protein entirely.
If we consider a specific example where a cytosine is replaced with an adenine, this is known as a point mutation rather than an insertion mutation. In such a case, the DNA's structure is altered because adenine pairs with thymine while cytosine normally pairs with guanine. The result of this substitution can affect the protein coded by the gene because a different amino acid may be incorporated at that position during translation.
An insertion mutation of three nucleotides can be less deleterious compared to an insertion of one nucleotide because the former may not lead to a frameshift. As codons are read in groups of three nucleotides, the insertion of three nucleotides can potentially add or delete a single amino acid without altering the reading frame of the subsequent codons.