Particulate inheritance is a pattern of inheritance discovered by

Mendelian genetics Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularized ...

theorists, such as

William Bateson William Bateson (8 August 1861 – 8 February 1926) was an English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscover ...

Ronald Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who a ...

Gregor Mendel Gregor Johann Mendel Order of Saint Augustine, OSA (; ; ; 20 July 1822 – 6 January 1884) was an Austrian Empire, Austrian biologist, meteorologist, mathematician, Augustinians, Augustinian friar and abbot of St Thomas's Abbey, Brno, St. Thom ...

himself, showing that

phenotypic trait A phenotypic trait, simply trait, or character state is a distinct variant of a phenotypic characteristic of an organism; it may be either inherited or determined environmentally, but typically occurs as a combination of the two.Lawrence, Eleano ...

s can be passed from generation to generation through "discrete particles" known as

genes In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

, which can keep their ability to be expressed while not always appearing in a descending generation.

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

biological diversity Biodiversity is the variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Eart ...

. They also did not understand how physical traits are inherited from one generation to the next.

Blending inheritance Blending inheritance is an obsolete theory in biology from the 19th century. The theory is that the progeny inherits any characteristic as the average of the parents' values of that characteristic. As an example of this, a crossing of a red flo ...

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 Pea (''pisum'' in Latin) is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable. Carl Linnaeus gave the species the scientific name ''Pisum sativum' ...

plants (''Pisum sativum'') to explain how variation can be inherited and maintained over time.

Blending model versus particulate model

* 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 * Particulate model: ** Offspring are a combination of both parents ** The characteristics of both parents are passed on to the next generation as separate entities ** Variation is maintained over time

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 Mendelian inheritance (also known as Mendelism) is a type of biological inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, and later popularized ...

, the Law of Independent Assortment, and the Law of Dominance:

Law of segregation

Mendel's experiment with tall and short pea plants demonstrates how each individual plant has two particles called

alleles An allele is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. Alleles can differ at a single position through single nucleotide polymorphisms (SNP), but they can also have insertions and deletions ...

. When a pea plant produces

gametes A gamete ( ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the Ge ...

(reproductive cells), it segregates one allele to each one.

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.

Law of dominance

In the pea plants, Mendel observed that the "T" allele ( dominant) masked the effects of the "t" allele (

recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...

). 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 In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

Fisher

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.

Notes

References

* Campbell, N. E. & Reece, J. B. (2002). ''Biology'' (6th ed.). San Francisco: Benjamin Cummings. * "Particulate inheritance." ''BioEd Online''. Retrieved 3-5-2009 fro
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{{DEFAULTSORT:Particulate Inheritance Classical genetics History of evolutionary biology