Parasitic chromosomes are "selfish"
chromosomes
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...
that propagate throughout cell divisions, even if they confer no benefit to the overall organism's survival. Parasitic chromosomes can persist even if slightly detrimental to survival, as is characteristic of some selfish genetic elements. Parasitic chromosomes are often
B chromosome
In addition to the normal karyotype, wild populations of many animal, plant, and fungi species contain B chromosomes (also known as supernumerary, accessory, (conditionally-)dispensable, or lineage-specific chromosomes). By definition, these chro ...
s, such that they are not necessarily present in the majority of the species population and are not needed for basic life functions, in contrast to
A chromosomes. Parasitic chromosomes are classified as
selfish genetic elements.
Parasitic chromosomes, if detrimental to an organism's survival, often are selected against by
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
over time, but if the chromosome is able to act like a selfish DNA element, it can spread throughout a population. An example of a parasitic chromosome is the b24 chromosome in
grasshoppers
Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago.
Grasshoppe ...
.
References
Genetics
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