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Acquired characteristics, by definition, are characteristics that are gained by an organism after birth as a result of external influences or the organism's own activities which change its structure or function and cannot be inherited.
Lamarck argued, as part of his theory of heredity, that a blacksmith's sons inherit the strong muscles he acquires from his work. [1]Lamarckism, also known as Lamarckian inheritance or neo-Lamarckism, [2] is the notion that an organism can pass on to its offspring physical characteristics that the parent organism acquired through use or disuse during its lifetime.
In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown-eye trait" from one of the parents. [1] Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype. [2]
The idea that such characteristics cannot be inherited is associated with a distorted understanding of the principle formulated by August Weismann, according to which somatic cells cannot transmit information to germ cells. In fact, Weisman admitted the possibility of environmental influence on the substance of heredity. [76]
Genetic traits located on gonosomes sometimes show specific non-Mendelian inheritance patterns. Individuals can develop a recessive trait in the phenotype dependent on their sex—for example, colour blindness and haemophilia (see gonosomal inheritances ).
Mutationism, along with other alternatives to Darwinism like Lamarckism and orthogenesis, was discarded by most biologists as they came to see that Mendelian genetics and natural selection could readily work together; mutation took its place as a source of the genetic variation essential for natural selection to work on. However, mutationism ...
Mendelian traits behave according to the model of monogenic or simple gene inheritance in which one gene corresponds to one trait. Discrete traits (as opposed to continuously varying traits such as height) with simple Mendelian inheritance patterns are relatively rare in nature, and many of the clearest examples in humans cause disorders.
Genetic characteristics have alternate forms, each inherited from one of two parents. Today these are called alleles. One allele is dominant over the other. The phenotype reflects the dominant allele. Gametes are created by random segregation. Heterozygotic individuals produce gametes with an equal frequency of the two alleles.