Hybrid growth disorders
Encyclopedia
Hybrid growth disorders refer to reduced growth or overgrowth in an organism that is a hybrid of two different species. In some sense, it is a type of hybrid dysgenesis when the growth disorder proves deleterious, thus making it the opposite of heterosis or hybrid vigour
.
Hybrid growth disorders may be referred to as a growth dysplasia, especially when resulting in overgrowth, although this terminology may be confusing since the term dysplasia
is commonly used to imply an impending cancer. However, a hybrid growth disorder is not caused by cancer.
A study on hybrid mice which investigated the possible causes for hybrid growth disorders revealed gene imprinting
to have a major effect. The study also showed that the growth disorder most commonly affected the heterozygous sex, as expected by Haldane's rule
. This would also explain why hybrid growth disorders often appear to affect one sex more than the other.
Heterosis
Heterosis, or hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring. The adjective derived from heterosis is heterotic....
.
Hybrid growth disorders may be referred to as a growth dysplasia, especially when resulting in overgrowth, although this terminology may be confusing since the term dysplasia
Dysplasia
Dysplasia , is a term used in pathology to refer to an abnormality of development. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells. Dysplasia is often indicative of an early neoplastic process...
is commonly used to imply an impending cancer. However, a hybrid growth disorder is not caused by cancer.
A study on hybrid mice which investigated the possible causes for hybrid growth disorders revealed gene imprinting
Imprinting (genetics)
Genomic imprinting is a genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner. It is an inheritance process independent of the classical Mendelian inheritance. Imprinted alleles are silenced such that the genes are either expressed only from the non-imprinted...
to have a major effect. The study also showed that the growth disorder most commonly affected the heterozygous sex, as expected by Haldane's rule
Haldane's rule
Haldane's rule or Haldane's law was formulated in 1922 by the British evolutionary biologist J.B.S. Haldane. It describes hybrid sterility in species and is extended to describe speciation in evolutionary theory, in two parts: the rule of hybrid sterility and the rule of hybrid inviability...
. This would also explain why hybrid growth disorders often appear to affect one sex more than the other.