Deletion (genetics)
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome.[1] Deletions can be caused by errors in chromosomal crossover during meiosis. This causes several serious genetic diseases.
Causes
Causes include the following:
- Losses from translocation
- Chromosomal crossovers within a chromosomal inversion
- Unequal crossing over
- Breaking without rejoining
For synapsis to occur between a chromosome with a large intercalary deficiency and a normal complete homolog, the unpaired region of the normal homolog must loop out of the linear structure into a deletion or compensation loop.
Types
Types of deletion include the following:
- Terminal Deletion - a deletion that occurs towards the end of a chromosome.
- Intercalary Deletion - a deletion that occurs from the interior of a chromosome.
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.
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.
Deletions are responsible for an array of genetic disorders, including some cases of male infertility and two thirds of cases of Duchenne muscular dystrophy.[1] Deletion of part of the short arm of chromosome 5 results in a syndrome called Cri du chat,[1] also known as "cry of the cat" syndrome. It is found in approximately 1 in 50,000 live births. The surviving infants have a distinctive cry, severe mental retardation, and shortened life span. Deletion mutations are also responsible for the cat family's inability to taste sweetness.
See also
References
Template:Chromosomal abnormalities
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