Deletion (genetics) - Effects

Effects

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 base 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 and two thirds of cases of Duchenne muscular dystrophy. Deletion of part of the short arm of chromosome 5 results in Cri du chat syndrome. Deletions in the SMN-encoding gene cause spinal muscular atrophy, the most common genetic cause of infant death.

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 are referred to as hCONDELs may be responsible for the anatomical and behavioral differences between humans,chimpanzees and other mammals.