In genetics

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, transgressive segregation is the formation of extreme phenotype

Phenotype

A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...

s, or transgressive phenotypes, observed in segregated hybrid populations compared to phenotypes observed in the parental lines.

Hybrid offspring generally possess traits or characteristics seen in ancestral species. These traits might be expected to be subdued or diluted when compared to the original species. Transgressive segregation attempts to explain situations when the converse is true, hybrid offspring that appear to have overstated traits when compared to the parental line.

Transgressive segregation may be a major source of novel adaptation

Adaptation

An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s in hybrids.

There are many causes of transgressive segregation in hybrids such as: recombination of additive alleles

Additive genetic effects

The additive genetic effect is an estimate of the quantitative change in a trait that is associated with substituting one allele with that of another allele within an interbreeding population. Additive effects are often calculated by genotyping and phenotyping offspring of a genetic test cross...

, an elevated mutation

Mutation

In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

 rate, reduced developmental stability, epistatic

Epistasis

In genetics, epistasis is the phenomenon where the effects of one gene are modified by one or several other genes, which are sometimes called modifier genes. The gene whose phenotype is expressed is called epistatic, while the phenotype altered or suppressed is called hypostatic...

 effects between allele

Allele

An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...

s, or overdominance

Overdominance

Overdominance is a condition in genetics where the phenotype of the heterozygote lies outside of the phenotypical range of both homozygote parents. Overdominance can also be described as heterozygote advantage, wherein heterozygous individuals have a higher fitness than homozygous individuals.An...

caused by heterozygosity at specific loci or chromosome number variation.