Final answer:
Deletions and insertions in DNA are most likely caused by errors during replication or recombination, leading to frameshift mutations that can significantly alter the function of a protein. An insertion or deletion that changes the number of nucleotides by a multiple of three is generally less detrimental because it does not cause a frameshift.
Step-by-step explanation:
The question you asked refers to which processes are most likely to create deletions and insertions in DNA. These types of mutations can happen through several cellular mechanisms, but they are often the result of errors during DNA replication or recombination. A deletion removes nucleotides from the DNA sequence, which can cause significant changes if it occurs within a gene. This is because the genetic code is read in codons, which are groups of three nucleotides. If a single nucleotide is deleted, the reading frame shifts, altering all subsequent amino acids, which is known as a frameshift mutation.
Insertion mutations occur when extra nucleotides are added into the DNA sequence, which can also lead to frameshifts if the number of nucleotides inserted is not a multiple of three. Frameshift mutations can be especially harmful to a cell because they typically result in a completely different, and often nonfunctional, protein being produced. The reason why an insertion of three nucleotides can be less detrimental than one of one nucleotide is that adding or removing three nucleotides does not alter the reading frame of the downstream codons, since three nucleotides constitute one complete codon.