Deletion (genetics)
A deletion ( engl. delete " delete " ), including gene deletion, is in genetics, a variant of the gene mutation and chromosome mutation (and thus a chromosome aberration) in which a nucleotide sequence or a portion of a nucleotide sequence is missing. A deletion is always a loss of genetic material. The number of deleted nucleic bases is not fixed, it can range from a single base ( point mutation ) to the entire chromosome.
A distinction is made between the interstitial and terminal deletion. The former describes a loss within the chromosome, the latter one being lost an end portion, that a portion of the Telomerbereiches.
Effects
As a result of the deletion, after the translation of the resulting mRNA from the DNA of a defective protein produced. As by the deletion of base pairs, a frame shift mutation is caused when a number of base pairs has been removed, which is not divisible by three.
However, if an entire codon / base triplet removed, most likely originates a faulty protein - as an amino acid is missing - but the reading frame is not shifted. Since it may happen also quite possible that the resulting protein is still partially functional and a weaker phenotype causes. A null mutation, however, would be the complete loss of gene function.
From microdeletions is when the piece of losses of chromosomes are so small that they (eg FISH test ) can be microscopically detected only by special techniques. If microdeletions damage several adjacent genes and thus trigger independent phenotypic effects, one speaks of a Contiguous gene syndrome.
Many deletions are also found in phenotypically inconspicuous (ie healthy ) individuals. Such polymorphisms are also called copy number variations (or in general structural variants ). An extensive catalog of such variants was published in the years 2010 and 2011 through the 1000 Genomes Project.
Indel
Similar effects to the deletion of the nucleotide sequences, the insert of additional sequences ( insertion). The combination of deletion and insertion of nucleotide sequences is in some cases not in the proportions of deletion or insertion resolvable and is referred to in these cases as Indel.
Example
- Partial deletion: Cri syndrome