Deletion mutations are genetic alterations that involve the removal of one or more nucleotides from a DNA sequence. These mutations can have significant effects on gene expression and protein synthesis. When a deletion mutation occurs, it can cause a frameshift mutation, which alters the reading frame of the DNA sequence. This means that the codons (groups of three nucleotides) are read in a different way, leading to a different amino acid sequence during translation.

The effects of deletion mutations are most pronounced during translation, which is the process by which the genetic information in mRNA is used to synthesize proteins. During translation, the mRNA molecule is read by ribosomes, and amino acids are added to the growing polypeptide chain based on the codons in the mRNA sequence.

Here's why the effects of deletion mutations are most significant during translation:

1. **DNA replication**: Deletion mutations that occur during DNA replication can be passed on to daughter cells, leading to genetic disorders. However, during replication, the DNA sequence is faithfully copied, so the effects of a deletion mutation are not immediately apparent.

2. **Transcription**: Transcription is the process by which DNA is converted into mRNA. Deletion mutations that occur during transcription can result in the production of a shorter mRNA molecule. However, since codons are read in groups of three, the effects of a deletion mutation may not be as severe as during translation.

3. **RNA processing**: RNA processing involves the modification of pre-mRNA molecules before they are transported out of the nucleus. Deletion mutations that occur during RNA processing can lead to the production of abnormal mRNA molecules. However, the effects of these mutations are still not as pronounced as during translation.

4. **Translation**: During translation, the mRNA sequence is read by ribosomes, and amino acids are added to the growing polypeptide chain. If a deletion mutation occurs, it can shift the reading frame, causing all subsequent codons to be read incorrectly. This results in a completely different amino acid sequence, which can significantly affect the structure and function of the resulting protein.

In conclusion, deletion mutations have the most significant effects during translation, as they can cause frameshift mutations and alter the amino acid sequence of the resulting protein. This can have profound implications for protein structure and function, potentially leading to genetic disorders or other abnormalities.