Why is translocation so important in plants
Chromosomal aberration (mutation)
Chromosome aberration is a random change in the structure or number of chromosomes.
A distinction is made between the following aberrations:
Structural aberration describes a change in the structure of the chromosome (chromosome mutation). This includes gene and point mutations.
The numerical aberration describes a change in the number of chromosomes (genome mutation).
Chromosome mutations are structural aberrations and arise when entire parts of the chromosome are remodeled. This includes:
- the loss of a part (deletion),
- the installation of an additional piece (insertion),
- the additional duplication of chromosomes (duplication),
- moving a section (translocation) and
- the upside down installation of a piece (inversion).
Some of these changes (duplication, deletion) can subsequently lead to serious illnesses or malformations, the others do not necessarily have to have consequences.
In the case of chromosome mutations, the position effect is also important: The change in the position of a gene can also have consequences, as it primarily influences gene regulation (changed position in relation to the promoter, etc.).
Gene mutations affect only a single gene and are the most common type of mutation. Here one or more bases on the DNA are changed, added or left out.
If only one base is changed, one speaks of one Point mutation. It arises through the exchange (substitution) of a base. Depending on the situation, this exchange can have no consequences (silent mutation) or, during coding, it can change the code in such a way that a different amino acid and thus a different, possibly malfunctioning protein is coded. In the worst case, this can have fatal consequences.
Point mutations in the non-coding region can negatively affect the function of stop codons or introns. Point mutations often arise from reading errors or from mutagenic substances (chemicals, radiation).
It becomes most unpleasant when the entire reading frame is shifted due to the loss (deletion) or addition (insertion) of one or more bases (Frameshift). Depending on the amount of removed or added bases, the code behind the mutation no longer makes sense, so that a completely different protein comes out during translation and can no longer fulfill its intended function. Therefore, the consequences can be significant. If the number of missing or new bases is divisible by three, the reading frame does not shift, even if amino acids are missing or added. The effect does not necessarily have to be serious.
The Gene duplication can occur in the event of a crossing over (crisscrossing of chromatids in meiosis) if the strands attached to one another are not homologous (matching one another, e.g. of the same length). The DNA is lengthened and the chromosome segment on the same strand is doubled, so that at the end of the day there are three identical genes instead of two. The consequences here are often severe congenital malformations, but they can also trigger positive developments within evolution.
Numerical aberrations are also known as genome mutations. Here there is a change in the number of chromosomes due to incomplete division during meiosis. The best known effect of a genome mutation is Down syndrome.
See also: mutation, chromosome set, DNA / nucleus, genome, chromatin.
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