VI.2.1 Molecular drive produces systematic shifts in the frequency of even those alleles that are not manifested in any way in the phenotype and evolutionary fitness of the individual.

Molecular drive is a process through which mutations can proliferate within gene families (in process of homogenetization) and within the population (in process of fixation of mutations) through a number of mechanisms of nonreciprocal transfer of genetic information occurring on the chromosome or between different chromosomes (Dover 1986). Molecular drive differs from genetic drift in that changes in the frequencies of the individual alleles that occur through its action are not random in their direction. If a certain population of genetically identical organisms is divided into several smaller populations, then genetic drift will lead to fixation of different alleles in each population. In contrast, the effect of molecular drive should lead to fixation of the same alleles in all populations. Molecular drive differs from selection in that the alleles that are fixed through its action need not favourably affect the phenotype of the organism and can thus have a zero or even negative impact on the biological fitness of the individual. 

            In molecular drive, one allele is replaced by another not because this is more advantageous for its bearer, but because, at the level of the DNA, it multiplies more effectively, either through a mechanism related to replication or through a mechanism related to gene conversion (see below).

            Molecular drive differs from mutation bias and reparation drive mainly in that it is responsible for the proliferation of certain mutations in the genome or in the gene pool of the population, but not for their repeated formation.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.