Genetic variation

New technology now allows scientists to directly sequence DNA, which has identified even more genetic variation than was previously detected by protein electrophoresis.

Variation and recombination can be facilitated by transposable genetic elements, endogenous retroviruses, LINEs, SINEs, etc.

[citation needed] For a given genome of a multicellular organism, genetic variation may be acquired in somatic cells or inherited through the germline.

A high mutation rate caused by the lack of a proofreading mechanism appears to be a major source of the genetic variation that contributes to RNA virus evolution.

[11] RNA recombination appears to be a major driving force in determining genome architecture and the course of viral evolution among Picornaviridae ((+)ssRNA) (e.g.

[12] In the Retroviridae ((+)ssRNA)(e.g. HIV), damage in the RNA genome appears to be avoided during reverse transcription by strand switching, a form of genetic recombination.

[16] Evolutionary biologists are often concerned with genetic variation, a term which in modern times has come to refer to differences in DNA sequences among individuals.

The concept of heritable variation—the presence of innate differences between life forms that are passed from parents to offspring, especially within categories such as species—does not rely on modern ideas of genetics, which were unavailable to 18th- and 19th-century minds.

In the mid-1700s, Pierre Louis Maupertuis, a French scholar now known primarily for his work in mathematics and physics, posited that while species have a true, original form, accidents during the development of nascent offspring could introduce variations that could accumulate over time.

[19] Simultaneously, French philosopher Denis Diderot proposed a different framework for the generation of heritable variation.

[22] Both Maupertuis and Diderot built on the ideas of Roman poet and philosopher Lucretius, who wrote in De rerum natura that all the universe was created by random chance, and only the beings that were not self-contradictory survived.

[24] Similarly, Lamarck's theory of the variability among living things was rooted in patterns of use and disuse, which he believed led to heritable physiological changes.

[17] Both Erasmus Darwin and Lamarck believed that variation, whether it arose during development or during the animal's life, was heritable, a key step in theories of change over time extending from individuals to populations.

[30] Darwin believed that species changed gradually, through the accumulation of small, continuous variations, a concept that would remain hotly contested into the 20th century.