Particulate inheritance: Difference between revisions

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{{Short description|Pattern of inheritance in evolutionary biology}}

[[File:Gregor_Mendel.jpg|right|thumb|199px|[[Gregor Mendel]], the Father of Genetics]]

[[File:Bateson2Gregor_Mendel.jpg|right|thumb|199px|William[[Gregor Mendel]], the Father of BatesonGenetics]]

[[File:William Bateson.jpg|upright|thumb|[[William Bateson]]]]

[[File:Youngronaldfisher2.JPG|thumb|right|200pxupright|[[Ronald Fisher]]]]

'''Particulate inheritance''' is a pattern of inheritance discovered by [[Mendelian genetics]] theorists, such as [[William Bateson]], [[Ronald Fisher]] or [[Gregor Mendel]] himself, showing that [[phenotypic trait]]s can be passed from generation to generation through "discrete particles" known as [[genes]], which can keep their ability to be expressed while not always appearing in a descending generation.<ref>[http://www.webref.org/anthropology/p/particulate_theory_of_inheritanc.htm "Particulate theory of inheritance"] {{Webarchive|url=https://web.archive.org/web/20160518143433/http://www.webref.org/anthropology/p/particulate_theory_of_inheritanc.htm |date=2016-05-18 }}, WebRef</ref>

== Scientific developments leading up to the theory ==

Early in the 19th century, scientists had already recognized that Earth has been inhabited by living creatures for a very long time. On the other hand, they did not understand what mechanisms actually drove [[Biodiversity|biological diversity]]. They also did not understand how [[Trait (biology)|physical traits]] are inherited from one generation to the next. [[Blending inheritance]] was the common ideal at the time, but was later discredited by the experiments of Gregor Mendel. Mendel proposed the theory of '''particulate inheritance''' by using [[pea]] plants (''Pisum sativum'') to explain how variation can be inherited and maintained over time.{{cn|date=March 2023}}

=== Blending model versus particulate model ===

* '''[[Blending inheritance|Blending model]]:'''

** Offspring are a blend of both parents (i.e. in modern terms, alleles would blend together to form a completely new allele)

** The characteristics of the blended offspring are passed on to the next generation

** Variation is washed out over time<ref name=bioed>{{cite web |author=Lisa M. Meffert |title=Blending Model of Inheritance vs. Particulate Model of Inheritance |work=Introduction to Mendelian Genetics |url=http://www.bioedonline.org/slides/content-slides/heredity/introduction-to-mendelian-genetics/?pageaction=displaySlideDetails&tk=30&dpg=2 |publisher=BioEd Online |accessdateaccess-date=March 12, 2014 |archive-url=https://web.archive.org/web/20160624175506/http://bioedonline.org/slides/content-slides/heredity/introduction-to-mendelian-genetics/?pageaction=displayslidedetails&tk=30&dpg=2 |archive-date=June 24, 2016 |url-status=dead }}</ref>

* '''Particulate model:'''

** Offspring are a combination of both parents

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== Mendel's methods ==

=== Mendel's laws ===

Since Mendel used experimental methods to devise his particulate inheritance theory, he developed three basic laws of inheritance: the [[Law of Segregation]], the [[Law of Independent Assortment]], and the [[Law of Dominance]]:<ref name=bioed/>

==== Law of segregation ====

Mendel's experiment with tall and short pea plants demonstrates how each individual plant has two particles called [[alleles]]. When a pea plant produces [[gametes]] (reproductive cells), it segregates one allele to each one.{{cn|date=March 2023}}

==== Law of independent assortment ====

The law states that when the parents differ from each other in two or more pairs of contrasting characters, the inheritance of one pair of characters is independent to that of the other pair of characters.<br/>{{cn|date=March 2023}}

==== Law of dominance ====

In the pea plants, Mendel observed that the "T" allele ([[dominance (genetics)|dominant]]) masked the effects of the "t" allele ([[recessive]]). The terms "dominant" and "recessive" are used for the masking and the covered allele, respectively. All offspring from this cross are [[heterozygotes]] in terms of their [[genotypes]]. They also are tall (because the allele for tall masks the allele for short) in terms of their "[[phenotype]]".<ref>{{cite web |author=Lisa M. Meffert |title=Crossing the Parental Lines: Female Contribution |work=Introduction to Mendelian Genetics |url=http://www.bioedonline.org/slides/content-slides/heredity/introduction-to-mendelian-genetics/?pageaction=displaySlideDetails&tk=30&dpg=6 |publisher=BioEd Online |accessdateaccess-date=March 12, 2014 |archive-url=https://web.archive.org/web/20160623133338/http://bioedonline.org/slides/content-slides/heredity/introduction-to-mendelian-genetics/?tk=30&dpg=6&pageaction=displayslidedetails |archive-date=June 23, 2016 |url-status=dead }}</ref>

== Fisher ==

{{further|Modern synthesis (20th century)}}

In the first chapter of his 1930 book ''[[The Genetical Theory of Natural Selection]]'' [[Ronald Fisher]] demonstrates that [[Mendelian inheritance]] shows that [[natural selection]] and not [[mutation]]s drive [[evolution]], and that it firmly discounted [[blending inheritance]], thus paving the way for the [[Modern evolutionary synthesis]].<ref>Fisher R. 1930. ''[[The Genetical Theory of Natural Selection]]'', Chapter 1.</ref>

In a 1918 publication titled "The Supposition of Mendelian Inheritance Among Close Relatives," [[R.A. Fisher]] showed that particulate inheritance was capable of generating the vast amount of variation we see among closely related individuals. This helped to reconcile the Biometric and Mendelian schools of thought at the time, and was an important step in the [[Modern synthesis (20th century)|modern synthesis]].<ref>{{cite book |last=Larson |first=Edward J. |authorlink=Edward J. Larson |year=2004 |title=Evolution: The Remarkable History of a Scientific Theory |series=Modern Library Chronicles |volume=17 |___location=New York |publisher=[[Modern Library]] |isbn=0-679-64288-9 |lccn=2003064888 |oclc=53483597 |pages=[https://archive.org/details/evolutionremarka00lars/page/221 221–243] |url-access=registration |url=https://archive.org/details/evolutionremarka00lars/page/221 }}</ref>

== Notes ==

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== References ==

* Campbell, N. E. & Reece, J. B. (2002). ''Biology'' (6th ed.). San Francisco: Benjamin Cummings.

* "Particulate inheritance." ''BioEd Online''. Retrieved 3-5-2009 from [http://www.bioedonline.org/slides/slide01.cfm?tk=60 BioEd Online Slides]

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{{DEFAULTSORT:Particulate Inheritance}}

[[Category:GeneticsClassical genetics]]

[[Category:History of evolutionary biology]]