Evolution

It is widely accepted that mimicry evolves as a positive adaptation. The lepidopterist and writer Vladimir Nabokov argued that although natural selection might stabilize a "mimic" form, it would not be necessary to create it. It may be that much of insect mimicry, including the Viceroy/Monarch mimicry, results from similar self-organizing processes, and thus the tendency for convergence by chance would be high.[73] The most widely accepted model used to explain the evolution of mimicry in butterflies is the two-step hypothesis. In this model the first step involves mutation in modifier genes that regulate a complex cluster of linked genes associated with large changes in morphology. The second step consists of selections on genes with smaller phenotypic effects and this leading to increasing closeness of resemblance. This model is supported by empirical evidence that suggests that there are only a few single point mutations that cause large phenotypic effects while there are numerous others that produce smaller effects. Some regulatory elements are now known to be involved in a supergene that is involved in the development of butterfly color patterns. Computational simulations of population genetics have also supported this idea.[ Vladimir Vladimirovich Nabokov (Russian: Влади?мир Влади?мирович Набо?ков, pronounced [vld?imr nbok?f] ( listen); 22 April [O.S. 10 April] 1899c – 2 July 1977) was a Russian American novelist.[1] Nabokov's first nine novels were in Russian. He then rose to international prominence as a writer of English prose. He also made serious contributions as a lepidopterist and chess composer. Nabokov's Lolita (1955) is his most famous novel, and often considered his finest work in English. It exhibits the love of intricate word play and synesthetic detail that characterised all his works. The novel was ranked at No. 4 in the list of the Modern Library 100 Best Novels.[2] Pale Fire (1962) was ranked at No. 53 on the same list. His memoir, Speak, Memory, was listed No. 8 on the Modern Library nonfiction list.[3] He was a finalist for the National Book Award for Fiction seven times, but ne

er won it. A supergene is a group of neighbouring genes on a chromosome which are inherited together because of close genetic linkage and are functionally related in an evolutionary sense, although they are rarely co-regulated genetically.[1] Supergenes have cis-effects due to multiple loci (which may be within a gene, or within a single gene's regulatory region), and tight linkage. They are classically polymorphic, and different elements code for different fitness effects which combine to form a coherent or epistatic whole. The two classic supergenes are (1) the Primula heterostyly locus, which controls "pin" and "thrum" types, and (2) the locus controlling Batesian mimetic polymorphism in Papilio memnon butterflies. For example, pin and thrum morphs of Primula have effects on genetic compatibility (pin style x thrum pollen, or thrum style x pin pollen matings are successful, while pin x pin, and thrum x thrum matings are rarely successful due to pollen-style incompatibility), and have different style length, anther height in the corolla tube, pollen size, and papilla size on the stigma. Each of these effects is controlled by a different locus in the same supergene, but recombinants are occasionally found with traits combining those of "pin" and "thrum" morphs. Gene complexes, in contrast, are simply tightly linked groups of genes, often created via gene duplication (sometimes called segmental duplication if the duplicates remain side-by-side). Here, each gene has similar though slightly diverged function. For example, the human major histocompatibility complex (MHC) region is a complex of tightly linked genes all acting in the immune system, but has no claim to be a supergene, even though the component genes very likely have epistatic effects and are in strong disequilibrium due in part to selection. No supergene has yet been characterized to the functional DNA level, but work is proceeding in a number of species. The earliest use of the term "supergene" may be in an article by A. Ernst (1936) in the journal Archiv der Julzus Klaus-stiftung fur Vererbungsforschung, Sozialanthropologie und Rassenhygiene.[