The correct answer to this question is Deletion. This chromosomal alteration is when DNA sequences are a loss. Many side effects can occur with Deletion. These effects can vary depending upon the location and size of the sequences which were deleted.
One impact that Deletion can have is affecting the gene dosage, which is the number of copies of a gene that are in a genome. Effecting a gene dosage can cause a phenotype. Another impact is that if the Deletion is large, the number of genes will be made will be high. This will increase the defect that is caused.