Subfunctionalization
Encyclopedia
Subfunctionalization is a model that explains the process by which duplicated genes
remain functional in a genome
. Duplicated genes
are frequently formed in eukaryotic
genome
s and are thought to be initially redundant in function. One of the extra copies is usually under relaxed selection
and therefore acquires degenerative mutation
s that render it nonfunctional. To explain the high percentage of duplicated genes
in eukaryotic
genomes several theories have been proposed, such as subfunctionalization. The DDC(Duplication-degenaration-complementation) subfunctionalization model was proposed by Force et al. and is derived from the fact that many genes have multiple independent subfunctions. According to the model after duplication the two copies of the gene acquire deleterious mutation
s that affect different subfunctions of the ancestral gene. Since both copies are needed to perform the function of the ancestral locus the duplicated loci
remain preserved through subfunctionalization. Compared to the ancestral locus, sub-function mutations have a low impact on individual relative fitness and therefore are neutral or nearly neutral to selection. Under such near neutrality genetic drift
plays a major role in the likelihood of subfunctionalized genes becoming fixed in the population.
Gene duplication
Gene duplication is any duplication of a region of DNA that contains a gene; it may occur as an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome.The second copy of the gene is often free from selective pressure — that is, mutations of it have no...
remain functional in a genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
. Duplicated genes
Gene duplication
Gene duplication is any duplication of a region of DNA that contains a gene; it may occur as an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome.The second copy of the gene is often free from selective pressure — that is, mutations of it have no...
are frequently formed in eukaryotic
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
s and are thought to be initially redundant in function. One of the extra copies is usually under relaxed selection
Selection
In the context of evolution, certain traits or alleles of genes segregating within a population may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively—meaning they contribute more offspring to the...
and therefore acquires degenerative 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...
s that render it nonfunctional. To explain the high percentage of duplicated genes
Gene duplication
Gene duplication is any duplication of a region of DNA that contains a gene; it may occur as an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome.The second copy of the gene is often free from selective pressure — that is, mutations of it have no...
in eukaryotic
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
genomes several theories have been proposed, such as subfunctionalization. The DDC(Duplication-degenaration-complementation) subfunctionalization model was proposed by Force et al. and is derived from the fact that many genes have multiple independent subfunctions. According to the model after duplication the two copies of the gene acquire deleterious 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...
s that affect different subfunctions of the ancestral gene. Since both copies are needed to perform the function of the ancestral locus the duplicated loci
Locus (genetics)
In the fields of genetics and genetic computation, a locus is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map...
remain preserved through subfunctionalization. Compared to the ancestral locus, sub-function mutations have a low impact on individual relative fitness and therefore are neutral or nearly neutral to selection. Under such near neutrality genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
plays a major role in the likelihood of subfunctionalized genes becoming fixed in the population.