Translocation
In genetics, chromosomal translocation refers to type of interchange of chromosome pieces of DNA following breakage, in which segments are transferred between nonhomologous chromosomes. When this exchange occurs without a net loss or gain of genetic material, it is called a balanced, or reciprocal, translocation, and there is no phenotypic change in the individual. When the exchange results in a deletion or duplication of chromosomal material, in gametes or somatic cells, severe phenotypic changes may result.
With chromosomal translocations, there is a physical movement of genes located on one segment of DNA to another location (locus) on another chromosomal segment of DNA. Because translocations involve changes to genes the are also termed translocation mutations.
In cell biology, translocation is a term also used to describe the movement of proteins or other substances through membranes. Translocation is also said to occur at the level of the ribosome during translation (protein synthesis) and involves the step-by-step movement along mRNA codons as each codon is read to determine which amino acid to insert into the lengthening protein chain. At the site of translation a translocation is said to occur as the mRNA moves one codon at a time through the ribosome complex (i.e., through the A site).
The process of ribosomal translocation involves specialized enzymes termed translocase enzymes.
Unbalanced chromosomal translocations, where the deleted segment, fragment, of portion of a chromosome attaches to another chromosome are rare in humans.
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