Final answer:
A deletion is defined as the loss of a chromosome segment, which can result in the absence of several to hundreds of genes, leading to genetic disorders.
Step-by-step explanation:
A deletion is best defined as the loss of a chromosome segment. This kind of chromosomal mutation results in a piece of the chromosome, which could contain several to hundreds of genes, being absent from the chromosome's structure. Deletion can have significant consequences since the lost DNA segment might contain multiple genes, potentially leading to a variety of genetic disorders. A deletion mutation can be especially detrimental depending on the genes involved and their functions. In the context of genetic diseases, a well-known example is the deletion mutation that causes two-thirds of cystic fibrosis cases by removing three nucleotides, and thus, the phenylalanine amino acid from the protein involved.