Inheritance of acquired characteristics

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Jean-Baptiste Lamarck

The inheritance of acquired characteristics is a hypothesis that physiological changes acquired over the life of an organism (such as the enlargement of a muscle through repeated use) may be transmitted to offspring. It is also commonly referred to as the theory of adaptation equated with the evolutionary theory of French naturalist Jean-Baptiste Lamarck known as Lamarckism.

History[edit]

The idea was proposed in ancient times by Hippocrates and Aristotle, and was commonly accepted near to Lamarck's time. Lamarck published his theory in 1809, the year Darwin was born. He noticed several lines of descent by comparing current species with fossil forms. He noticed that the older the fossils were, the more alike they were to modern species. Two ideas were incorporated in Lamarck’s theory. The first was the theory of use and disuse; the idea that body parts used more often become stronger and larger, while parts not used slowly waste away and disappear. The second idea was the inheritance of acquired characteristics theory, the concept that modifications that occur during an organism's lifetime are passed on to its offspring. His example was the giraffe. He believed that the long neck of the giraffe resulted from the ancestors of giraffes stretching their necks longer and longer while trying to reach the highest branches of the trees.[1] Comte de Buffon, before Lamarck, proposed ideas about evolution involving the concept, and even Charles Darwin, after Lamarck, developed his own theory of inheritance of acquired characters, pangenesis. The basic concept of inheritance of acquired characters was finally widely rejected in the early 20th century.

In the 1920s, Harvard University researcher William McDougall studied the abilities of rats to correctly solve mazes. His reports claimed that offspring of rats that had learned the maze were able to run it faster. In his data, the first rats would get it wrong 165 times before being able to run it perfectly each time, but after a few generations, it was down to 20. McDougall attributed this to some sort of Lamarckian evolutionary process. However McDougall's results have never been replicated by other experimenters, and have been criticised for having several methodological problems and poor record-keeping.[2][3]

During the rule of Joseph Stalin in the USSR in the 1930s, the theory of inheritance of acquired characteristics was central to the dogma put forth by Trofim Lysenko, president of the Soviet Academy of Agricultural Sciences. Lysenkoism was advanced primarily in service to Soviet agriculture, always resulting in dismal failure.

Recently, researchers have reexamined this concept in light of discoveries in epigenetics and transgenerational epigenetics. The study of Heijmans et al (2008) studied people born during the Dutch Hunger Winter in 1944–1945. Adults who were conceived during the famine had distinct epigenetic marks that their siblings born before or after the famine did not. These marks reduced the production of insulin-like growth factor 2 (IGF2), affected the children's growth. While transgenerational epigenetic inheritance could have occurred, the findings could also be explained by in utero modifications due to famine, rather than germline inheritance.[4] Further, environmental stress in experimental mice that caused aggressive behavior in males caused the same behavior in their offspring, who had DNA methylation patterns changes for particular genes.[5]

The mechanism of transgenerational epigenetic inheritance appears to involve long noncoding RNAs (lncRNAs), which are transcripts generally expressed from regions that are thought not to code for proteins. Some lncRNAs bind to transcripts from protein coding genes. Associated chromatin-remodeling proteins than modify local chromatin and DNA through mechanisms such as DNA methylation, suppressing gene expression.Kevin Morris's 2012 article in the Scientist [6] discusses heritability of epigenetic changes in depth.

See also[edit]

Citations[edit]

  1. ^ Campbell, Neil; Reece, Jane (March 2011) [2002], "22", Biology (Sixth ed.), Benjamin Cummings, p. 431 
  2. ^ WE Agar, FH Drummond, OW Tiegs, MM Fourth (final) report on a test of McDougall's Lamarckian experiment on the training of rats Journal of Experimental Biology, 1954
  3. ^ FAE Crew A repetition of McDougall's lamarckian experiment Journal of genetics, 1936
  4. ^ B.T. Heijmans et al., “Persistent epigenetic differences associated with prenatal exposure to famine in humans,” Proceedings of the National Academy of Sciences USA, 105:17046–49, 2008
  5. ^ T.B. Franklin, I.M. Mansuy, “Epigenetic inheritance in mammals: evidence for the impact of adverse environmental effects,” Neurobiol Dis, 39:61–65, 2010.
  6. ^ Kevin V. Morris. "Lamarck and the Missing Lnc". The Scientist, Oct 1, 2012. URL: http://www.the-scientist.com/?articles.view/articleNo/32637/title/Lamarck-and-the-Missing-Lnc/

References[edit]

  • Campbell, Neil; Reece, Jane (March 2011) [2002], "22", Biology (Sixth ed.), Benjamin Cummings, p. 431