Chromosomal Mutations

Beyond changes confined to a single gene, the genetic material can also be altered on a much larger, chromosome-wide scale, either by changing how many chromosomes a cell has or by rearranging the internal structure of one or more chromosomes; both kinds of change are collectively called chromosomal mutations or chromosomal aberrations. The distinction between a gene mutation and a chromosomal mutation is one of scale: a gene mutation alters the sequence within a single gene and is never visible under an ordinary microscope, whereas a chromosomal mutation alters a region spanning many genes at once and, because it changes the size, shape or number of whole chromosomes, can often be detected directly by microscopic examination in addition to genetic analysis. Chromosomal mutations are conventionally split into two major groups: changes in chromosome number, where chromosomes are gained or lost without necessarily altering their internal str …