What is the overdominance hypothesis?
Overdominance hypothesis: The overdominance hypothesis states that an organism that descends from parents of different genetic backgrounds will have greater resistance to a broader spectrum of potential dangers.
What is the main difference between the dominance and overdominance hypothesis?
The dominance hypothesis can explain the deterioration from inbreeding and the recovery on outcrossing. The overdominance hypothesis demands a kind of gene action that is rare, but even if only a small minority of loci are of this type, they may be a major factor in population variance and heterosis.
Who proposed the dominance hypothesis of heterosis?
Charles Davenport
The dominance hypothesis was proposed by Charles Davenport (1908),which is the most widely accepted hypothesis among the other explanations for heterosis.
What is overdominance and example?
In particular, the phenomenon known as overdominance occurs when a heterozygote has a more extreme phenotype than that of either of its parents. A well-known example of overdominance occurs in the alleles that code for sickle-cell anemia.
What is overdominance in heterosis?
According to quantitative genetic theory, heterosis can result from dominance, overdominance, or epistasis. Overdominance is an intra-allelic interaction in which the presence of multiple alleles leads to greater performance than homozygosity for either allelic state.
What type of selection does overdominance exert on a population?
Directional selection
Directional selection, overdominance, and underdominance are types of frequency-independent selection in which the fitness of a genotype is independent of its frequency in the population; these contrast with positive and negative frequency-dependent selection, in which the fitness of a genotype depends on the genotype …
What is dominance hypothesis of heterosis?
The dominance hypothesis attributes heterosis to canceling of deleterious or inferior recessive alleles contributed by one parent, by beneficial or superior dominant alleles contributed by the other parent in the heterozygous genotypes at different loci (Davenport 1908; Bruce 1910; Jones 1917).
What is heterosis breeding?
Heterosis refers to the phenomenon that progeny of diverse varieties of a species or crosses between species exhibit greater biomass, speed of development, and fertility than both parents.
What is overdominance heterosis?
The genetic overdominance hypothesis states that some combinations of alleles (which can be obtained by crossing two inbred strains) are especially advantageous when paired in a heterozygous individual. In any case, outcross matings provide the benefit of masking deleterious recessive alleles in progeny.
How do you determine overdominance?
Overdominance. Overdominance occurs when fitness of the heterozygote is superior to that of either homozygote. The result is that both alleles are maintained in the population at an equilibrium frequency ( , read “q hat”, where q = 0) that maximizes fitness.
What is overdominance in evolution?
Overdominance is a condition in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Possessors of the deleterious allele have lower life expectancy, with homozygotes rarely reaching 50 years of age.