The four types of alterations of chromosome structure are deletion, duplication, inversion, and reciprocal translocation. Deletion is the loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome. Duplication is repition of a part of a chromosome resulting from fusion with a fragment froma homologous chromosome. Duplication can result from an error in meiosis or from mutagenesis. Inversion is a change in a chromosomeresulting from reattachment of a chromosome fragment to the original chromosome, but in a reverse direction. Mutagens and errors during mesosis can cause inversions. Translocation is the attachment of a chromosomal fragment to a nonhomologous chromosome.