Small deletions are less likely to be fatal; large deletions are usually fatal – there are always variations based on which genes are lost. Some medium-sized deletions lead to recognizable human disorders, e.g.
Williams syndrome. Deletion of a number of pairs that is not evenly divisible by three will lead to a
frameshift mutation, causing all of the
codons occurring after the deletion to be read incorrectly during
translation, producing a severely altered and potentially nonfunctional
protein. In contrast, a deletion that is evenly divisible by three is called an
in-frame deletion. Deletions are responsible for an array of genetic disorders, including some cases of male
infertility, two thirds of cases of
Duchenne muscular dystrophy, Deletion of part of the short arm of chromosome 5 results in
Cri du chat syndrome. Some syndromes, including Angelman syndrome and Prader-Willi syndrome, are associated with both microdeletions and genomic imprinting, meaning that same microdeletion can cause two different syndromes depending on which parent the deletion came from. Recent work suggests that some deletions of highly conserved sequences (CONDELs) may be responsible for the evolutionary differences present among closely related species. Such deletions in humans, referred to as
hCONDELs, may be responsible for the anatomical and behavioral differences between humans,
chimpanzees and other varieties of mammals like
ape or
monkeys. Recent comprehensive patient-level classification and quantification of driver events in
TCGA cohorts revealed that there are on average 12 driver events per tumor, of which 2.1 are deletions of
tumor suppressors. ==Detection==